Java Library @ TechLads

Liferay 6- Scheduler Engine design change

2010-09-28T11:56:00.001+05:30

In Liferay 5.2.x, we had com.liferay.portal.kernel.job.IntervalJob as a Quartz scheduler job, which needs to be implemented for different jobs we need for Quartz trigger execution.

In Liferay 6, the design pf scheduler engine has been changed and introduced combination with JMS. I have prepared the small class cum collaboration diagram, which can help understanding how we need to make triggers now onwards.

Basically, they made use of messaging with Quartz. The Job class for liferay is now fixed which is com.liferay.portal.scheduler.job.MessageSenderJob .

Now we have a com.liferay.portal.kernel.messaging.MessageListener which is to be implemented for different job handling.

The schedulerEnginUtil class will register the listener with perticular queue destination and schedules new trigger as per the SchedulerEntry details with MessageSenderJob. When trigger fired, this Job class will eventually sends message to queue, which will eventually go to the listener.

This time, not as like previous scheduler, they have given exposure to Message which can contain some payload data if needed for job execution. This is very helpful sometimes.

By default the method schedule(SchedulerEntry schedulerEntry, ClassLoader classLoader)from SchedulerEngineUtil sends null Message. So, we might need to copy and pass some payload object if needed.

Liferay Struts Portlet: Usage of SessionErrors class...

2010-09-07T17:55:00.002+05:30

This is very common issues we come across when we want to change portal code with extension environment. Mostly we do is, copying the code from portal to ext and making new struts portlet.

And for sending errors to pages, we use SessionErrors.add(...) method, which will eventually forward to default error.jsp file. So you will never find what is happening. Simple thing, to make this working fine, is...

- Make new empty page named error.jsp in your portlet.

- Make new Struts-config and tiles-def entry of your new JSP in ext.

- From your render method, forward to the new file when you have SessionErrors filled with errors like,


 if (!SessionErrors.isEmpty(req)) {
  return mapping.findForward("portlet.portlet_name.error");
 }

See this link to understand the detailed problem...

http://www.liferay.com/community/forums/-/message_boards/message/113965

Liferay: Exposing Webservice & access using Axis Client...

2010-08-31T15:27:00.000+05:30

Basically in liferay, we create services using service builder, which is like child's play. In service.xml, we need to put local and remote both attributes, and it will generate class for web service also.

The link shows steps,

- To generate web services using service builder.

- To generate WSDD changes.

- To access web service from Axis client

More @ http://arvindm.com/2010/03/23/web-services-in-liferay/

Liferay Wrapper Plugins ...

2010-08-20T13:54:00.002+05:30

Very nice article about liferay core functionality extension. You can create wrappers around core services and it will be in service when you compile-deploy it! Isn't that's great? Check the link.

Liferay Wrapper Plugins

Liferay: Make Custom "Add Application" portlet ...

2010-08-17T17:16:00.001+05:30

Sometimes client will amaze us by giving very very complex requirements which not seem to be a value adding thing. But still we need to complete it as it's our work :). Same happened here, when i need to make a portlet replicating the "Add Application" liferay portlet.

Though its not new, it has given me chance to see how "Add Application" menu works.

Basically liferay uses a Javascript file named layout_configuration.js to call the layout_configuration portlet.

Liferay has in-built portlet named layout_configuration for this functionality. It renders the same using LayoutConfiguration.toggle('87'); where 87 is the portlet ID.

Find the following portlet in file portal\portal-web\docroot\WEB-INF\liferay-portlet.xml,

 <portlet>  
         <portlet-name>87</portlet-name>  
         <icon>/html/icons/default.png</icon>  
         <struts-path>layout_configuration</struts-path>  
         <use-default-template>false</use-default-template>  
         <show-portlet-access-denied>false</show-portlet-access-denied>  
         <show-portlet-inactive>false</show-portlet-inactive>  
         <restore-current-view>false</restore-current-view>  
         <private-request-attributes>false</private-request-attributes>  
         <private-session-attributes>false</private-session-attributes>  
         <render-weight>50</render-weight>  
         <system>true</system>  
     </portlet>

Also find the portlet in file \portal\portal-web\docroot\WEB-INF\portlet-custom.xml as below,

 <portlet>  
         <portlet-name>87</portlet-name>  
         <display-name>Layout Configuration</display-name>  
         <portlet-class>com.liferay.portlet.StrutsPortlet</portlet-class>  
         <init-param>  
             <name>view-action</name>  
             <value>/layout_configuration/view</value>  
         </init-param>  
         <expiration-cache>0</expiration-cache>  
         <supports>  
             <mime-type>text/html</mime-type>  
         </supports>  
         <resource-bundle>com.liferay.portlet.StrutsResourceBundle</resource-bundle>  
     </portlet>

You will find the path layout_configuration in files struts-config.xml and tiles-defs.xml in the same folder.

In struts-config,

     <!-- Layout Configuration -->  
     <action path="/layout_configuration/templates" forward="portlet.layout_configuration.templates" />  
     <action path="/layout_configuration/view" forward="portlet.layout_configuration.view" />

In tiles-defs,

 <!-- Layout Configuration -->  
 <definition name="portlet.layout_configuration" extends="portlet">  
     <put name="portlet_decorate" value="false" />  
 </definition>  
 <definition name="portlet.layout_configuration.templates" path="/portlet/layout_configuration/templates.jsp" />  
 <definition name="portlet.layout_configuration.view" extends="portlet.layout_configuration">  
     <put name="portlet_content" value="/portlet/layout_configuration/view.jsp" />  
 </definition>

At first I started learning what liferay is doing. Basically in this portlet, liferay generates the HTML layout of all portlets in liferay-display.xml as per the category. It makes the whole tree structure of categories and subcategories. This portlet is not described in liferay-disaply.xml, so it will not be disaplayed in the tree.

Then it loads this portlet on onclick event of "Add Application" menu click. It calls the portal servlet at url /portal/render_portlet, which will render the portlet and shows the result HTML in popup dialog.

Check the javascript function from layout_configuration.js file,

 toggle: function(ppid) {  
         var instance = this;  
         var plid = themeDisplay.getPlid();  
         var doAsUserId = themeDisplay.getDoAsUserIdEncoded();  
         if (!instance.menu) {  
             var url = themeDisplay.getPathMain() + '/portal/render_portlet';  
             var popupWidth = 250;  
             var body = jQuery('body');  
             body.addClass('lfr-has-sidebar');  
             instance._dialog = Liferay.Popup(  
                 {  
                     width: popupWidth,  
                     message: '<div class="loading-animation" />',  
                     position: [5,5],  
                     resizable: false,  
                     title: Liferay.Language.get("add-application"),  
                     onClose: function() {  
                         instance.menu = null;  
                         body.removeClass('lfr-has-sidebar');  
                     }  
                 }  
             );  
             jQuery.ajax(  
                 {  
                     url: url,  
                     data: {  
                         p_l_id: plid,  
                         p_p_id: ppid,  
                         p_p_state: 'exclusive',  
                         doAsUserId: doAsUserId  
                     },  
                     success: function(message) {  
                         instance._dialog.html(message);  
                         instance._loadContent();  
                     }  
                 }  
             );  
         }  
     }

After that, the javascript adds click and drag-drop even for all portlet divs of that popup dialog. So that user will be able to add the portlet into page by click OR drag-drop.

I need to show list of portlets of specified categories only without the categories.So i need to copy this portlet as it is and filter as per the category.

First of all i choosen the plugins environment for my new portlet, but it failed because i need to use the static resource named WebAppPool as per the code below,


PortletCategory portletCategory = (PortletCategory)WebAppPool.get(String.valueOf(company.getCompanyId()), WebKeys.PORTLET_CATEGORY);

This pool is maintained by liferay, it has all the categories on server startup. Now liferay loads the war file of plugin portlet when we add the portlet in page. So new classloader will be used here. And in java, child classloader can't access parent classloader's resources.

So i decided to move to ext environment. I made the new "Custom Add Application" portlet in ext with some code changes.

1. Need to filter the categories, for that i used portlet's init-param to define my including categories as below,

 <init-param>  
         <name>includeCategories</name>  
         <value>myCategory,yours</value> <!-- Comma seperated category names, sub-categories will not be filtered...-->  
     </init-param>

2. Changed the code in view.jsp, included the categories only given in the init-param of above step and will show in HTML un-ordered list. Sent all categories to view_category.jsp.

3. Changed the code in view_category.jsp, displayed the portlets from all categories of above step as HTML list-items. It only shows portlets, ignoring the categories from view.

4. Same JS file has been used with different name to keep the drag-drop support for portlet list-items. Changed the JS file accordingly. Like ID for the result element is passed because now we don't want it to be in popup dialog etc...

5. Made new theme from classic, and changed the navigation.vm to show the above portlet as navigation menu item.

Though this was not extra-ordinary development, i got the chance to look into some internals of Liferay's odd style of developing a complex product, which may give us harsh times if touched :) (Isn't its too complex for a portal?).

Some Useful Linux commands while deploying...

2010-08-03T18:00:00.003+05:30

While deploying any WAR in tomcat on Linux platform, most problem we have faced is Linux terminal commands. In all industries you will mostly have a Linux server for test server,staging server etc...So most of the times developers need to test the code locally and then deploy it in centralized test OR development server where other can access and test it.

The steps will be same for all programmers. We get an email from so called IT people with deployment instruction having IP, username ,password (Which is always weird and we always copy paste it :)) etc... We Linux into the server using Putty or some other terminal client. But most of windows developers will face problem here. So some commands which are very easy to remember are,


- cd (Same as windows)
- pwd (Shows current working dir)
- ./ (this folowing with script filename, will execute the script. You can also use 'su')
- ps ax (Shows running process details, with process ID. like windows task manager shows.)
- grep hi (Finds the string 'hi')
- kill -9 567 (Kills process with ID 567)

Now in Linux if you have many servers running and you want to stop only specific one then you can use following combination,

- ps ax|grep projDir (This will show the process having projDir in sys variable.)

After that we can kill that process easily.

Before running startup.sh you must have set variable for JAVA_HOME, so that tomcat can find the java env.

There are other commands which are for changing file permissions (Read only, executable etc...) but will post it later.

-- Update By Kunal --

- scp sourcepath user@destserverhost:destpath (Secure copy of file from one linux server to another)

Example

scp /root/example.html root@66.235.111.88:/home/example

Spring MVC portlet with annotations

2010-07-30T18:06:00.000+05:30

Java portlet framework is awesome for portal developers. Different portal frameworks are there which supports portlet development in their environment. They also support spring portlet. Spring's portlet support is exposed through Spring MVC interface. Spring provides MVC based portlet development which is so easy and neatly architectured.

Spring provides class org.springframework.web.portlet.DispatcherPortlet which is to be difined in portlet.xml.

  <portlet>  
     <description xml:lang="en">Portlet Description</description>  
     <portlet-name>portlet-name</portlet-name>  
     <display-name xml:lang="en">Portlet Display Name</display-name>  
     <portlet-class>org.springframework.web.portlet.DispatcherPortlet</portlet-class>  
     <init-param>  
       <name>contextConfigLocation</name>  
       <value>/WEB-INF/appContext.xml</value>  
     </init-param>  
     <expiration-cache>0</expiration-cache>  
     <supports>  
       <mime-type>text/html</mime-type>  
       <portlet-mode>VIEW</portlet-mode>  
     </supports>  
     <portlet-info>  
       <title>Portlet Name</title>  
       <short-title>Portlet Name</short-title>  
       <keywords>Spring Portlet MVC</keywords>  
     </portlet-info>  
   </portlet>

The init param contextConfigLocation defines the application context XML file to be loaded for this portlet. This file has the spring bean definition for classes implementing Controller interface OR annotated classes with @Controller.

Annotated Controller class is as follows,

 @Controller  
 @RequestMapping  
 public class MyController {  
   
     private static final Logger _LOG = Logger.getLogger(MyController.class);  
       
     //Default render method will call this method...  
     @SuppressWarnings("unchecked")  
     @RequestMapping({"VIEW","/demoportlet/jsp2.do"})  
     public Object defaultRender(Model model, PortletRequest request,RenderResponse response) {  
         response.setContentType("text/html; charset=UTF-8");  
         String action = request.getParameter("action");  
         if("action1".equals(action)) {  
              ...  
             return "demoportlet/jsp1";  
         } else {              
              ...  
             return "demoportlet/jsp2";  
         }  
     }  
       
     // Direct request mapping based on action parameter value = 'someAction'  
     @RequestMapping(params = "action=someAction")   
     public Object actionOne(RenderRequest actionRequest, RenderResponse actionResponse) throws Exception {  
         actionResponse.setContentType("text/html; charset=UTF-8");  
          ...          
         return "demoportlet/jsp2";  
     }  
 }

In web.xml we need to define a servlet org.springframework.web.servlet.DispatcherServlet and org.springframework.web.servlet.ViewRendererServlet for JSP resolving as follows,

<servlet>  
     <servlet-name>view-servlet</servlet-name>  
     <servlet-class>org.springframework.web.servlet.ViewRendererServlet</servlet-class>  
     <load-on-startup>1</load-on-startup>  
  </servlet>  
    
  <servlet>  
  <servlet-name>normal</servlet-name>  
  <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>  
  <load-on-startup>1</load-on-startup>  
  </servlet>   
   
  <servlet-mapping>  
  <servlet-name>normal</servlet-name>  
  <url-pattern>*.do</url-pattern>  
  </servlet-mapping>   
    
  <servlet-mapping>  
     <servlet-name>view-servlet</servlet-name>  
      <url-pattern>/WEB-INF/servlet/view</url-pattern>  
  </servlet-mapping>

In order for DispatcherPortlet rendering to work, you must declare an instance of the ViewRendererServlet .

In the Portlet MVC framework, each DispatcherPortlet has its own WebApplicationContext, which inherits all the beans already defined in the root WebApplicationContext. These inherited beans can be overridden in the portlet-specific scope, and new scope-specific beans can be defined local to a given portlet instance.

The DispatcherServlet will look for normal-servlet.xml as we declared its name as 'normal'. This file will contain the definitions for beans which are needed to handle the portlet scanning, annotation handling etc... So first of all, the request will come to DispatcherServlet as its Spring MVC, and then it will scan for portlet controllers using spring's <context:component-scan> tag.

We also need to define the context param contextConfigLocation in web.xml which is loaded by DispatcherServlet on server startup. This will have all the beans required by portlets.

 <context-param>  
  <description>Spring Context XML location</description>  
  <param-name>contextConfigLocation</param-name>  
  <param-value>classpath:conf/spring/global.xml</param-value>  
  </context-param>

The normal-servlet.xml will look like follows, where we need to define beans for annotation handling.

 <beans xmlns="http://www.springframework.org/schema/beans"  
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
     xmlns:context="http://www.springframework.org/schema/context"  
     xmlns:util="http://www.springframework.org/schema/util"  
     xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd  
         http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd  
         http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd">  
           
     <context:annotation-config />          
   
     <bean id="localeResolver" class="org.springframework.web.servlet.i18n.CookieLocaleResolver">  
       <property name="cookieName" value="lang"/>  
       <!-- in seconds. If set to -1, the cookie is not persisted (deleted when browser shuts down) -->  
       <property name="cookieMaxAge" value="100000"/>  
     </bean>  
   
     <bean id="localeChangeInterceptor"  
    class="org.springframework.web.servlet.i18n.LocaleChangeInterceptor">  
       <property name="paramName" value="locale"/>  
     </bean>  
       
     <bean class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping">  
         <property name="interceptors">  
             <list>  
                 <ref bean="localeChangeInterceptor"/>  
             </list>  
         </property>  
         <property name="order" value="10" />  
     </bean>    
     
   <bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"/>  
       
     <context:component-scan base-package="com.spring.controller" />      
 </beans>

The <context:component-scan> will finds the controller classes from given package which are annotated with @Controller.

Other than is, we need to enter portlet information in portal framework's configuration files in which we want to deploy and use this portlet. When we add portlet from the portal, the controller methods will get call.

Display tag - Opensource JSP paging library...

2010-07-28T17:42:00.001+05:30

Paging is important part when we have much data to show at once. We need to do all hectic coding for paging, like keep the total count, then count total pages to be shown, keep total records per page etc... This is nothing new but repeating and it takes bit time. So why not use some lib which gives you all of this with basic tags?

Note from the homepage : "The display tag library is an open source suite of custom tags that provide high-level web presentation patterns which will work in an MVC model. The library provides a significant amount of functionality while still being easy to use."

Basic steps to use are:

1. Get the jar file from http://displaytag.sourceforge.net and put it in classpath.

2. In your JSP page write following import for taglib.

 <%@ taglib uri="http://displaytag.sf.net" prefix="display" %>

3. Check the following code for displaying the list of Objects as table with paging. You can configure different propeties of table as below, also can define CSS classes for diff. tags.


 <display:table name="lstObject" defaultsort="1" pagesize="20" sort="external" partialList="true"   
     size="totalCount" uid="lstObject" id="myObject"  
             export="false" requestURI="<%=someUrl%>" class="data">   
               
             <!-- For detailed understanding for each property, check the link http://displaytag.sourceforge.net/1.2/configuration.html -->  
             <display:setProperty name="paging.banner.placement" value="both" />  
             <display:setProperty name="paging.banner.group_size" value="10" />      
             <display:setProperty name="paging.banner.no_items_found">  
                 <span class="lfloat">No {0} found.</span>  
             </display:setProperty>  
             <display:setProperty name="paging.banner.one_item_found">  
                 <span class="lfloat">One {0} found.</span>  
             </display:setProperty>              
             <display:setProperty name="paging.banner.all_items_found">  
                 <span class="lfloat">{0} {1} found, displaying all {2}.</span>  
             </display:setProperty>  
             <display:setProperty name="paging.banner.some_items_found">  
                 <span class="lfloat">{0} {1} found, displaying {2} to {3}.</span>  
             </display:setProperty>              
             <display:setProperty name="paging.banner.full">  
                 <div class="paging_footer">  
                     <div class="rfloat">  
                         <div class="lfloat" style="padding-top:6px;">[<a href="{1}">First</a> | <a href="{2}">Prev</a>]</div>  
                         <div class="paging_wrap lfloat">                          
                             {0}                          
                         </div>  
                         <div class="rfloat" style="padding-top:6px;">[<a href="{3}">Next</a> | <a href="{4}">Last</a>]</div>  
                     </div>  
                 </div><br>  
             </display:setProperty>  
             <display:setProperty name="paging.banner.first">  
                 <div class="paging_footer">  
                     <div class="rfloat">  
                         <div class="lfloat" style="padding-top:6px;">[First | Prev]</div>  
                         <div class="paging_wrap lfloat">  
                              {0}  
                         </div>  
                         <div class="rfloat" style="padding-top:6px;">[<a href="{3}">Next</a> | <a href="{4}">Last</a>]</div>  
                     </div>  
                 </div><br>  
             </display:setProperty>          
             <display:setProperty name="paging.banner.last">                  
                 <div class="paging_footer">  
                     <div class="rfloat">  
                         <div class="lfloat" style="padding-top:6px;">[<a href="{1}">First</a> | <a href="{2}">Prev</a>]</div>  
                         <div class="paging_wrap lfloat">                          
                             {0}  
                         </div>  
                         <div class="rfloat" style="padding-top:6px;">[Next | Last]</div>  
                     </div>  
                 </div><br>  
             </display:setProperty>  
             <display:setProperty name="paging.banner.onepage" value="" /> <!-- Because dont want to show any value if only one page...-->  
               
             <display:setProperty name="paging.banner.page.selected">  
                 <div class="lfloat">  
                     <a onclick="return false;" class="active" href="javascript:void(0);">{0}</a>  
                 </div>  
             </display:setProperty>                      
             <display:setProperty name="paging.banner.page.link">  
                 <div class="lfloat">  
                     <a href="{1}" title="Goto page {0}">{0}</a>  
                 </div>  
             </display:setProperty>  
               
             <display:setProperty name="paging.banner.page.separator" value=" " />    <!-- Seperator between page numbers ,, i.e this will show "[First | Prev] 1 2 3 [Last | Next]"-->          
             <% MyObject myObject = (MyObject)pageContext.getAttribute("myObject"); %> <!-- Get the object from pageContext, which is writter in 'id' attribute -->  
              <display:column title="My title" class="first">  
              <!-- An y HTMl or jsp scriptlet can be used here... -->  
              </display:column>  
              <display:column property="name" title="2nd Column"/>  
              <display:column title="3rd Column"><%= myObject.getSomeValue() %></display:column>  
              ...               
         </display:table>

4. The displaytag table can be used as follows. Where,

- pagesize is total records per page

- sort="external" means list given is sorted

- size defined the total records for which paging will be done

- name defines the list object for which the table will be generated

- id means internal object for each row which can be used in JSP scriptlets to do some data manipulations.

 <display:table name="lstObject" defaultsort="1" pagesize="20" sort="external" partialList="true"   
     size="totalCount" uid="lstObject" id="myObject"  
             export="false" requestURI="<%=someUrl%>" class="data">  
             ...  
             </display:table>

5. You can set any property for display tag as below. You can also write HTML inside the property tag. For detailed understanding for each property this library supports, check the link - http://displaytag.sourceforge.net/1.2/configuration.html

 <display:setProperty name="paging.banner.page.separator" value=" " />

HomePage: http://displaytag.sourceforge.net

Configuration properties: http://displaytag.sourceforge.net/1.2/configuration.html

Liefray: Using JSONObject for Ajax in Plugin Portlet...

2010-06-09T15:32:00.000+05:30

Many times we face situations when we need to use Ajax call from JSP pages. Using jQuery, its very easy to call any JSP through AJAX. You can just call the JSP and show its response from callback into some DOM element.

 $.ajax({  
      type: 'POST',  
      url: getUrl(),  
      data: {},                                   
      success: function(returnData) {  
          $('#someElementId').html(returnData);  
      }  
     });

But this is useful when you want some big data OR some complex UI layout which is hard to generate using callback javascript function. Simple we call the JSP in which we have already designed the layout properly so we don't need to bother about manipulating the returnData in javascript.

Now think if you only need some small amount of data from server side, how will go? Making a new JSP for such a small task is not worhty i think. One technology is there for our help,JSON. JSON is a simple string notation of any object, which represents key-value pair like hashmap but uses its own structure to define objects.

Liferay provides com.liferay.portal.struts.JSONAction class which is a struts Action class. But to use this one in portlet we need to configure the portlet as a com.liferay.portlet. But there is one more way to use JSON with plugin portlet, using overriding serveResource method from GenericPortlet class into your portlet class.

 protected void getSomeDataAsJson(ResourceRequest request, ResourceResponse response)  
 throws PortletException, IOException {  
     String myParam = ParamUtil.getString(request, "myParam","");  
     // Some service call using params from request...  
     Obj obj = getDataFromSomeService(myParam);  
     JSONObject jsonObj = JSONFactoryUtil.createJSONObject();  
     // obj can be anything... Integer,Boolean,String or some custom POJO...  
     jsonObj.put("testData", obj);  
     OutputStream os = response.getPortletOutputStream();  
     try {  
         os.write(jsonObj.toString().getBytes());  
     }  
     finally {  
         os.close();  
     }  
 }  
 @Override  
 public void serveResource(ResourceRequest request, ResourceResponse response)  
         throws PortletException, IOException {  
     String cmd = ParamUtil.getString(request,Constants.CMD);  
     if ("getSomeDataAsJson".equals(cmd)) {  
         getSomeDataAsJson(request, response);  
     }  
 }

The above method will provide the JSON object as a result in javascript callback function. Check the Ajax call,

 $("input:button[@name='<portlet:namespace />SomeThing']").click (function() {  
     $('#<portlet:namespace />myDiv').text("");  
     //URL which goes to your portlet...  
     var url = "<portlet:resourceURL><portlet:param name='<%=Constants.CMD %>' value='getSomeDataAsJson' /></portlet:resourceURL>";      
     //Append your hidden input fields in the resourceURL...   
     url +="&"+$('input:hidden').serialize();   
     $.ajax({  
             url: url,  
             data: {},  
             dataType: 'json',  
             success: function(message) {  
                     $('#<portlet:namespace />myDiv').text(message.testData);  
                     }  
             }  
         );      
     });

This way we don't need to create JSPs for small data fetching. Show other ways also using simple AJAX calling (Like DWR supports, direct calling JAVA class method from JS and returns data in JS callback).

Javascript-ajax RSS feed reader - using jQuery with jGFeed ...

2010-06-04T14:55:00.001+05:30

Check the new version of Ajax feed reader, which is using jQuery with jGFeed.

 <html><head>  
 <script type="text/javascript" src="http://code.jquery.com/jquery-1.4.2.min.js"></script>  
 <script type= "text/javascript" language='javascript'>  
 //<![CDATA[  
 (function($) {  
   $.extend( {  
 jGFeed : function(url, fnk, num, key) {  
       // Make sure url to get is defined  
       if (url == null) return false;  
       // Build Google Feed API URL  
       var gurl = "http://ajax.googleapis.com/ajax/services/feed/load?v=1.0&callback=?&q="+url;  
       if (num != null) gurl += "&num="+num;  
       if (key != null) gurl += "&key="+key;  
       // AJAX request the API  
       $.getJSON(gurl, function(data) {  
         if (typeof fnk == 'function')  
           fnk.call(this, data.responseData.feed);  
         else  
           return false;  
       });  
     }  
   });  
 })(jQuery);  
 var strArr = ['http://www.thinkdigit.com/forum/external.php?type=RSS','http://www.snapfiles.com/feeds/sf20fw.xml',  
        'http://www.download.com/3410-2001-0-10.xml','http://www.download.com/3412-2001-0-10.xml',  
        'http://www.download.com/3412-2003-0-25.xml','http://www.videohelp.com/rss/tools',  
        'http://www.videohelp.com/rss/forum','http://www.pcstats.com/rss/rss.xml','http://feeds.feedburner.com/Techdudes',  
        'http://feeds.feedburner.com/jQueryHowto'];  
 var isXml = true;  
 function loadXml() {  
   var index = Math.floor(Math.random()*strArr.length);  
   getJsonData(strArr[index],'targetDiv');  
 }  
 //loadXml();  
 function getJsonData(dataSource, divId) {  
   $.jGFeed(dataSource,  
   function(feeds) {  
     if (!feeds) {  
       alert('there was an error');  
     }  
     var html = "";  
     for (var i=0;i<feeds.entries.length;i++) {  
       var entry = feeds.entries[i];  
       var title = entry.title;  
       var link = entry.link;  
       var description = entry.contentSnippet;  
       var pubDate = entry.publishedDate;  
       html += "<div class='entry'><h4 class='postTitle'><a class='fancy block' href='" + link + "' target='_blank'>" + title + "</a></h4>";  
       // html += "<em class='date'>" + pubDate + "</em>";  
       var categories = " Lables : ";  
       if (entry.categories && entry.categories.length>0) {  
         categories += entry.categories[0];  
         for (var j=1;j<entry.categories.length;j++) {  
           categories +=", " +entry.categories[j];  
         }  
         html += "<p><b>"+categories+"</b></p>";  
       }  
       html += "<p class='description'>" + description + "</p></div>";  
     }  
     var btn = "<input type='button' value='Reload' onclick='getJsonData(\""+dataSource +"\",\""+divId+"\");' /></br>";  
     $('#'+divId).html(btn + html);  
   },  
   50);  
 }  
 function cleartDiv(divId) {  
   var obj = document.getElementById(divId);  
   if (obj) {  
     //obj.style.display = 'none';  
     obj.innerHTML="";  
   }  
 }  
 function getNewData(url,divId) {  
   if (url!=0) {  
     if (!url) {  
       var index = Math.floor(Math.random()*strArr.length);  
       getJsonData(strArr[index],divId);  
     } else {  
       getJsonData(url,divId);  
     }  
   }  
 }  
 //window.setInterval("getNewData()", 7000); // update the data every 20 mins  
 //]]>  
 </script>  
 </head>  
 <body onload="getNewData('http://www.videohelp.com/rss/tools','targetDiv');">  
     <select onchange="javascript:getNewData(this.options[this.selectedIndex].value,'targetDiv');" size="9" style="width:25%;">  
         <option value='0' selected="selected">Please Select</option>  
         <option value='http://www.thinkdigit.com/forum/external.php?type=RSS'>ThinkDigit.com</option>  
         <option value='http://www.snapfiles.com/feeds/sf20fw.xml'>SnapFiles.com</option>  
         <option value='http://www.articlecity.com/xml/main.xml'>ArticleCity.com</option>  
         <option value='http://www.download.com/3410-2001-0-10.xml'>Download.com populars</option>  
         <option value='http://www.download.com/3412-2001-0-10.xml'>Download.com New</option>  
         <option value='http://www.download.com/3412-2003-0-25.xml'>Download.com 25 New Titles</option>  
         <option value='http://feeds.feedburner.com/Techdudes'>TechDudes</option>  
     </select>  
     <div id="linkDiv" style="width:98%;height:25px;overflow:auto;"/>  
     <div id="targetDiv" style="border:dashed 1px;background:#fafafa;width:70%;height:450px;overflow:auto;font-family:verdana;font-size:10px;"/>  
 </body>  
 </html>

jGFeed: http://plugins.jquery.com/project/jgfeed

jQuery - usage of $.bind method...

2010-06-02T14:50:00.000+05:30

jQuery is widely used javascript library which provides easy ways to do complex things. By using simple Javscript, it takes too much time to code it, but jQuery simple it down to few lines.

To check multiple Checkboxes, i have written the following code.

 <script type="text/javascript" src="html/js/jquery.js"></script>  
 <script type="text/javascript">  
 //on load, register events for checkboxes...  
 $(document).ready(  
      function() {       
           $('#chk_all').change(checkAll);            
           $('form[@name="fm"] input:checkbox[@name!="chk_all"]').each (function(index) {  
                $(this).change(selectForDelete);  
           });  
      }  
 );  
 function checkAll(){  
      var isCheck = this.checked;  
      $('form[@name="fm"] input:checkbox[@name!="chk_all"]').each(function(){  
           this.checked = isCheck;  
           $(this).trigger("change");  
      });  
 }  
 function selectForDelete(){  
      var alertIdsObj = $('form[@name="fm"] input[@name="deleteIds"]');  
      if (this.checked) {  
           if (alertIdsObj.val().indexOf(this.value)==-1) {  
                if(alertIdsObj.val()=='') {  
                     alertIdsObj.val(''+this.value);  
                } else {  
                     alertIdsObj.val(alertIdsObj.val()+","+this.value);  
                }  
           }  
      } else {  
           if (alertIdsObj.val().indexOf(this.value)>=0) {  
                alertIdsObj.val(alertIdsObj.val().replace(this.value+',',''));  
                alertIdsObj.val(alertIdsObj.val().replace(','+this.value,''));  
                alertIdsObj.val(alertIdsObj.val().replace(this.value,''));  
           }  
      }  
 }  
 //Function called for item details...  
 function viewAlertDetails(alertId) {  
           $.ajax({  
            type: 'POST',  
            url: getUrl()+"&alertId="+alertId+"&cmd=detailed-market-alerts",  
            data: {},                                           
            success: function(returnData) {  
                 $('#-mainDiv').hide();  
                 $('#-detailsDiv').html(returnData);  
                 $('#-detailsDiv').show();       
            }  
           });       
 }  
 function getUrl() {  
      var url = new String(document.location);  
      var index = url.indexOf("?");  
      if (index!=-1) {  
           url = url.substring(0,index);  
      }  
      return url;  
 }  
 //function called from second page to go back to first page with latest data...  
 //Repalces the old content with new  
 function viewAlerts() {  
      $.ajax({  
            type: 'POST',  
            url: getUrl(),  
            data: {},                                           
            success: function(returnData) {       
                var myData = $(returnData).find('#-mainDiv').html();  
                $('#-mainDiv').html(myData);  
                $('#chk_all').bind('change', checkAll);  
                $('form[@name="fm"] input:checkbox[@name!="chk_all"]').each (function(index) {            
                     $(this).bind('change',selectForDelete);            
                });  
                $('#-detailsDiv').html("");  
                $('#-detailsDiv').hide();  
                $('#-mainDiv').show();  
                return true;  
            }  
           });       
      return false;  
 }  
 </script>

The flow is as below,

- First page shows list of data.

- By clicking particular item from the list, i hides the mainDiv and shows details of the item in detailsDiv using $.ajax.

- By clicking "Back" button from detailsDiv, i again loads the main page using $.ajax.

The problem is, when i go to second page and comes on the first page using $.ajax,i change the HTML content of mainDiv with the latest data in viewAlerts() javascript function as $('#-mainDiv').html(myData);.

If you check the script, you will notice that i have registered the event handling for checkboxes in the document,One for main checkbox and one for all other checkboxes of the list, using $(document).ready() jQuery function. Event handling works fine at first page. But when we change the html content of the div afterwards, event handler automatically removed.

So to re-enable the events on checkboxes,we need to use following code in viewAlerts() javascript function.

 $('#chk_all').bind('change', checkAll);  
 $('form[@name="fm"] input:checkbox[@name!="chk_all"]').each (function(index) {  
      $(this).bind('change',selectForDelete);            
 });

$(jQueryDomObj).bind(eventName,function) is very useful if you want to manipulate the element contents using javascript.

HibernateDaoSupport with HibernateTemplate - defaultAutoCommit set false...

2010-06-01T21:40:00.000+05:30

I am working on a web application which needs hibernate for DB integration. So i decided to use hibernate with spring. As we all know that Spring is very lightweight and supports hibernate in an easy way. Also i am used to spring JdbcDaoSupport for DB integration and StoredProcedure class for SQL Server stored procedures.

While working this time i decided to use HibernateDaoSupport. Your DAO class must extend this class to use HibernateTemplate class.

Steps to make DAO using this,

- Extend HibernateDaoSupport and also an interface if you have.
- Define your methods which provides different Database operations (CREATE, DELETE, FETCH, UPDATE, INSERT etc...)
- Define required beans as below,

 <bean id="dataSource"  
 class="org.apache.commons.dbcp.BasicDataSource">  
  <property name="driverClassName">  
   <value>com.mysql.jdbc.Driver</value>  
  </property>  
  <property name="url">  
   <value>jdbc:mysql://localhost/testdb</value>  
  </property>  
  <property name="username" value="username" />  
  <property name="password" value="passwordforit" />  
  <property name="defaultAutoCommit" value="true" />  
  <property name="defaultTransactionIsolation" value="2" />  
  <property name="maxActive" value="100" />  
  <property name="maxIdle" value="50" />  
  <property name="minIdle" value="50" />  
  <property name="maxWait" value="100" />  
  <property name="initialSize" value="20" />  
 </bean>  
 <!-- Database Property -->  
 <bean id="hibernateProperties"  
 class="org.springframework.beans.factory.config.PropertiesFactoryBean">  
  <property name="properties">  
   <props>  
    <prop key="hibernate.hbm2ddl.auto">update</prop>  
    <prop key="hibernate.dialect">  
    org.hibernate.dialect.MySQLDialect</prop>  
    <prop key="hibernate.show_sql">true</prop>  
    <prop key="hibernate.cache.provider_class">  
    net.sf.ehcache.hibernate.EhCacheProvider</prop>  
   </props>  
  </property>  
 </bean>  
 <!-- Hibernate SessionFactory -->  
 <bean id="sessionFactory"  
 class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">  
  <property name="dataSource">  
   <ref local="dataSource" />  
  </property>  
  <property name="hibernateProperties">  
   <ref bean="hibernateProperties" />  
  </property>  
  <!-- OR mapping files. -->  
  <property name="mappingResources">  
   <list>  
    <value>myMapping.hbm.xml</value>  
   </list>  
  </property>  
 </bean>  
 <bean id="MyDAOTarget" class="com.dao.MyDAO">  
  <property name="sessionFactory">  
   <ref bean="sessionFactory" />  
  </property>  
 </bean>

- Define transactionManager for transaction managment as below,

 <bean id="transactionManager"  
 class="org.springframework.jdbc.datasource.DataSourceTransactionManager">  
  <property name="dataSource">  
   <ref bean="dataSource" />  
  </property>  
 </bean>

- Define org.springframework.transaction.interceptor.TransactionProxyFactoryBean as below, which will eventually make proxy bean on the class given in target property.

 <bean id="MyDAO" class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean">   
   <property name="transactionManager">   
     <ref bean="transactionManager"/>  
   </property>   
   <property name="target">   
     <ref bean="MyDAOTarget"/>  
   </property>   
   <property name="transactionAttributes">  
     <props>   
       <prop key="insert*">PROPAGATION_REQUIRED, ISOLATION_READ_COMMITTED</prop>  
       <prop key="update*">PROPAGATION_REQUIRED, ISOLATION_READ_COMMITTED</prop>   
       <prop key="delete*">PROPAGATION_REQUIRED, ISOLATION_READ_COMMITTED</prop>  
       <prop key="find*">PROPAGATION_REQUIRED, ISOLATION_READ_COMMITTED, readOnly</prop>   
     </props>   
   </property>  
 </bean>

- Use getHibernateTemplate().get(Class entityClass,Serializable id) OR getHibernateTemplate().load(Class entityClass,Serializable id) to load particular enoty from Database.
- Use getHibernateTemplate().find(String queryString,Object value) to find entities using HQL/SQL query.
- Use getHibernateTemplate().delete(), getHibernateTemplate().deleteAll() for removing entities from Database.
- Use getHibernateTemplate().update() OR getHibernateTemplate().saveOrUpdate() for updating/inserting entity in the Database.

It seems so easy right? But no, wait! All these works fine when you have <property name="defaultAutoCommit" value="true" /> . When you change this property to false, all updates to database will not take effect. Because in that case we need to begin and commit transaction form the code.

I have tried using getHibernateTemplate() for update operations but it failed. It doesn't work with transactions. So try as per the following method.

 public void updateMyObj(MyObj myObj) {  
   Session session = getSession(true);// true means allow create new session if required.  
   Transaction trans = session.beginTransaction();  
   session.saveOrUpdate(myObj);  
   trans.commit();  
 }

Same thing works for any update operation. This is really strange, i tried for one whole day using getHibernateTemplate() but it never worked with <property name="defaultAutoCommit" value="false" />.

Java Wildcards Vs. Generics...

2010-05-27T22:18:00.001+05:30

I have never used wildcards in java until i read this.

Let's say I have a super class Vehicle and few sub classes like Scooter, Bike, Car, etc... Now I need to have a list of vehicles, my first thought would be something like:

 List<Vehicle> lstVehicles;

Instead, some people are recommending something like:

 List<? extends Vehicle> lstVehicles;

Why should I use wildcards instead of simple generics?

Because Java generics are invariant.

Suppose we have B extends A:

* B is a subtype of A
* an instanceof B is also an instanceof A

Since Java arrays are covariant:

* B[] is a subtype of A[]
* an instanceof B[] is also an instanceof A[]

However, Java generics are invariant:

* List<B> is NOT a subtype of List<A>
* a instanceof List<B> is NOT an instanceof List<A>.

Wildcards are used to make it more flexible while preserving type safety.

*
List<B> is a List<? extends A>

References:
Wildcards
Generics
Generics and subtyping
More fun with wildcards

Java String manipulation: Appending empty string to 'var.subString(x,y)' saves memory...

2010-05-21T15:50:00.004+05:30

In java usually we do SubString operation as follows.

    String strMainData = "Some long String..." ;
    String strSub= strMainData.subString(i,j); // Where i and j are index values...

This operation will keep the reference to same object strMainData,but only returns smaller string as per the indexes. So it uses same memory as the original String.

We should use it as follows.

    String strSub = new String(strMainData.subString(i,j));

    String strSub = strMainData.subString(i,j) +"";

This will only keep the reference to new smaller String and removes reference to original String variable.

More @ StackOverflow

Singleton refactored:Initialization on demand holder idiom...

2010-05-21T15:14:00.002+05:30

Hey guys, check this out. I found this while searching around different styles for singleton pattern. It basically provides on demand loading of the instance.

public class Something {
 private Something() {
 } 
 private static class LazyHolder {
  private static final Something INSTANCE = new Something();
 } 
 public static Something getInstance() {
  return LazyHolder.INSTANCE;
 }
}

The static class LazyHolder is only executed when the static method getInstance is invoked on the class Something, and the first time this happens the JVM will load and initialize the LazyHolder class. The initialization of the LazyHolder class results in static variable INSTANCE being initialized by executing the (private) constructor for the outer class Something.

More @ Wiki

Hibernate : One-to-many Parent-Child relationships...

2010-05-21T06:50:00.000+05:30

Hibernate is quite good ORM framework. When we need one-to-many relationship in hibernate, we need to take ArrayList or Set. If the structure is kind of tree, then hibernate can perform wired if not properly tweaked.

Basically if you are having some sort of many to one relationships structure from child to parent. In hibernate all depends on mapping. Tweak your mapping, Use One-to-many relationship from parent to child using java.util.Set.

Do not use ArrayList because List is ordered, so hibernate will add extra column for that ordering only.
Also check your lazy property. If you load parent and you have set lazy="false" on its child set property (variable which is of type Set), then all of its children will be loaded from DB which can affect the performance.

Also check 'inverse' property for children. If inverse is true in child table, that means you can manage the child entity separately. Otherwise you have to do that using the parent only.

AXIS2 web service client - without sub/proxy ...

2010-05-20T17:00:00.002+05:30

This article is regarding how to call an web service without modifying the client each time for diff. web service OR method call. Basically we use stub/proxy classes for diff. web service method calls using Axis2, but internelly it calls using XML SOAP envelopes. So, we can direcftly convert the client to use Axis2 API classes and provide an implementation which only needs to handle the response from the call. Response will be in XML format,so we need to fetch data from XML. We can covnert XML into Pojos using Castor or JAXB libs.

You can directly use ServiceClient class to call web service, which provides call using XML only and returns XML response. For different methods of web service, you have to convert the XML response to some java POJO to use it. Only Response handling needs to be done at your end. that you can do like from XML to Map etc...

So you won't need any other stub classes to call any web service, only needs to handle response XML or converted POJO.

This is the way you don't need to modify your client every time for diff. web services. You can develop like providing a response handler to client externally. So that for every different web service you will have diff. response handler class which is implementation of you interface.

//common interface for response handlers...
//implement this for diff. web service/methods

public interface WSRespHandler{
    public Object getMeResp(Object respData);
}

//pass particular handler to client when you call some WS
public class WebServiceClient {
    public Object getResp(WSRespHandler respHandler) {
        ...
        return repHandler.getMeResp(xmlData);
    }
}

References:

http://www.developer.com/java/web/article.php/3863416/Using-Axis2-and-Java-for-Asynchronous-Web-Service-Invocation-on-the-Client-Side.htm

http://www.devdaily.com/blog/post/java/java-web-service-client-read-array-list/

Facebook integration in your web application...

2010-05-20T13:43:00.004+05:30

This is not regarding only java, you can do this on any web application in different languages also.

Facebook is getting popular now a days. Almost every site has facebook login enabled, so that if the user has facebook account he can login using that and can use the site as a registered user. For this the user must allow the site to use his facebook user data (Friends list, profile details etc...). Facebook provides different set of APIs to do such integration with your site.

It basically provides different client APIs which are based on different technologies lke PHP, Java, Javascript etc.. Here i will show you how to integrate facebook only using javascript API, which is the best way to do this.

1. First step is, you have to include the javascript from FB as follows.

        <script type="text/javascript"
        src="http://static.ak.connect.facebook.com/js/api_lib/v0.4/FeatureLoader.js.php"></script>

2. You have to init the Facebook JS library with you facebook API key and provide the XDReceiver url. XDReceiver.htm is provided by facebook which is to be uploaded on you server to handle the callback to Facebook's javascript functions. It will store facebook cookies on your server so that you can access the facebook session in your site to fetch facebook data for the logged in user.

        FB.init("myApiKey","/html/xd_receiver.htm", {
        "doNotUseCachedConnectState" : false
        ,"reloadIfSessionStateChanged" : true    //Reloads the page if user logs in OR out
        ,"ifUserConnected" : showFacebookInviteLink()    //Is user connects to FB, executes the provided JS function          
        });

3. Now you need to call function which will provide the facebook login popup for user. User can login into facebook and then allows the application to use his/her data.

        FB.Connect.requireSession(); // This will give the popup to login
      
        // This will check if FB is initiated with application key and user logged in or not. On user session, it will executes the function.
        FB.ensureInit(function() {
            FB.Facebook.get_sessionState().waitUntilReady(
                    function() {
                        
            });
          
        });

    4. To logout from Facebook, you just need to call JS function FB.Connect.logout();

    Now you can access different functions of the FB JS library to acces any data it supports to use on your site/application having session initiated.I will show how to show invite friends popup dialog on your site/application. Call the below function on invite button/link click event.

       function inviteFacebookFriends() {      
        FB.ensureInit(function() {
            FB.Facebook.get_sessionState().waitUntilReady(
                function() { //on Connect succes
                        var fbml = "";
                        fbml = '<fb:fbml>\n'
                                + '<fb:request-form\n'
                                //Redirect back to this page                           
                                + ' action="'+document.location+'"\n'                           
                                + ' method="POST"\n'
                                + ' invite="true"\n'
                                + ' type="app test invite"\n'
                                + ' content="app test inviting...\n'                           
                                + '
                                + ' label=\'Join me!\' />"\n'
                                + '>\n'           
                                + ' <fb:multi-friend-selector\n'
                                + ' rows="2"\n'
                                + ' cols="4"\n'
                                + ' bypass="Cancel"\n'
                                + ' showborder="false"\n'   
                                + ' exclude_ids="excludeIds"\n'           
                                + ' actiontext="Use this form to invite your friends to connect to my site."/>\n'
                                + ' </fb:request-form>' + ' </fb:fbml>';
                      
                        var dialog = new FB.UI.FBMLPopupDialog("Invite Friends To This Site",fbml);                                      
                        dialog.setContentWidth(650);
                        //dialog.setContentHeight(450);
                        dialog.show();
            });
        });  
    }

Thats it! This will show the standard popup dialog for friends invitation. Basically this FBMl will be rendered by facebook js API.Now user can select any of his friends and send them invitation to join your site. Let me know if you have any queries OR problems, will try to help around.

Telnet Client part 2 - using Apache net implementation...

2009-03-15T00:27:00.000+05:30

I have shown Telnet client using socket programming which is my own logic.But Apache has already done this for us in their Net package which is freely available to download.So we can use that org.apache.commons.net.telnet.TelnetClient class for using telnet connection.

Its a very simple class.You can download its source and can figure out what they have done. Though i will show simple usage for it.

TelnetClient tc = new TelnetClient(); tc.connect("localhost", 23);

Then you can register a listener thread to get response from the telnet connection shown above. For full examples, check out java2s

Its nothing new, but a good implementation what we understood so far.
If you want totally command prompt like session for telnet, then you must wait for response from execution of the given command.Then only the next command will be sent over, as we do in DOS/Terminal.So for that we must have a logic which check the input stream and receives response.

Telnet client with java...

2008-12-20T13:20:00.000+05:30

Telnet is very important utiliy we use.We can call remote server commands and use different services running on perticular port.Mostly telnet server runs on 23,but can be differed .

Through java, if we want to make remote connection over some port then we have two different ways.

1. Use windows/linux telnet command line utility (which is same on both win and linux... :).)

OR

2. Use socket programming using java.net package.

In first way, we need to get hands on the process.We can achieve that using

Process p = Runtime.getRuntime().exec(<system command or exe path>)

But i don't think this should be used for telnet like communication,because telnet requires continuous session running on remote server and executing you commands.Sometimes it can be so that after executing several commands,you need to rollback so you can cancle all the commands.so its a continuous and sequential process most of the times.The Process class used can be out of our hands anytime if the executable crashes or if anything bad happen(Mostly..the exe crash...).

So, we have another,'Socket' way here, which connects to perticular host on given port number and try to open TCP connection with it.If the host is listening on port and connection accepted,then we can send our commands to the host.(I know, i know, that we all know sockets since our starting graduation days :) ,but let me tell guys... ).

There are two ways to make a telnet client using Sockets.
1.Make it CLI based,means which accepts every input from Command Line Interface entered by user.
2.Make it automated,which takes command list from some file or database,generates a script or list of commands and run it whole on host.

First one is quite easy,i think you all might have done that :).Just let me tell you little what to do...

1.CLI based Telnet...

Socket soc = new Socket(host,port); DataInputStream din=new DataInputStream(soc.getInputStream()); PrintWriter dout = new PrintWriter(soc.getOutputStream(),true); BufferedReader br=new BufferedReader(new InputStreamReader(System.in));

See,we have taken InputStream of socket and made a PrintWriter on the OutputStreamof it to send commands.Also we have taken BufferedReader for user inputs from CL.

... .... do { char[] buffer = new char[8192]; int mark = bReader.read(buffer); StringBuffer sb = null; for(int i=0;i<buffer.length;i++){ char c = buffer[i]; if(c!='\0'){ //To avoid null characters printed... if(sb == null){ sb = new StringBuffer(buffer.length); } sb.append(c); } } System.out.print((sb!=null)?sb.toString():"-- No Response --"); Command=br.readLine(); //takes commands from CL by user... if(!Command.equals("quit")) { dout.println(Command); } }while(!Command.equals("quit")); //exit the loop if user sends 'quit'... ...

This gives you same telnet as you got in your OS, so i think its simple but good to know :)

2.Automated Telnet...

It will be almost same,except we will have a ArrayList/Array of commands in hand before we create Socket.And then change the loop onto the list to execute all the commands one after another...

int j=-1; String[] commands = new String[5]; ... .... do { j++; char[] buffer = new char[8192]; int mark = bReader.read(buffer); StringBuffer sb = null; for(int i=0;i<buffer.length;i++){ char c = buffer[i]; if(c!='\0'){//To avoid null characters printed... if(sb == null){ sb = new StringBuffer(buffer.length); } sb.append(c); } } System.out.print((sb!=null)?sb.toString():"-- No Response --"); Command = commands[j]; if(Command==null || Command.length()<0) break; dout.println(Command+"\n"); }while(j<commands.length); ...

So this will executes all commands in commands Array of String.

So folks,this ends our telnet socket :).Same like this we can make client or scripts for FTP automation.It helps in real time situation when you need to make some jobs for backup,export/import files on remote host etc...Waiting for you responses...

Snmp4J - Java library for SNMP Communication...

2008-12-17T22:53:00.000+05:30

We all know that if we need to use more on socket programming in java then we must use native code in c++.SNMP (Simple network Management Protocol) is used for communication with the network devices.Any network device can be queried using SNMP request.Snmp4j is the library which provides you implementation to make SNMP requests.

We can query any device (Switch,PC etc...) if it has a SNMP agent running,which will handle our SNMP request and respond with the proper data.This library made it so easy for us without looking into much details of SNMP.

In basic,SNMP is used for getting information (GET requests),but sometimes it can be used to set values in the device (SET requests).Assume that every device has a list of pre-defined variables in it,which are called OID(Object IDs).These OIDs will have a specific structure (which is called MIB file,which seems like a tree structured as in registry).

OID looks like 1.3.6.1.4.1.318.1.1.1.12.3.2.1.3.1, which has a special meaning.It has a description(name) and an associated value in it.When you query particular OID (i.e 1.3.6.1....),it will give its associated value.You can set its value also (if its allowed ;)).OIDs also have communities(Public,Private etc...) which shows permissions.Mostly public community is allowed to be viewed by SNMP requests.

See the example below how to make a SNMP request,

import org.snmp4j.*;

...
...

OctetString communityName = new OctetString("public");

String ipAddressUrl = strIpAddress+"/"+161; //161 is used for SNMP Agent...

Address targetAddress = new UdpAddress(ipAddressUrl);

TransportMapping transport = new DefaultUdpTransportMapping();

Snmp snmp = new Snmp(transport);

snmp.listen();

CommunityTarget target = new CommunityTarget();

target.setAddress(targetAddress);
target.setRetries(3);
target.setTimeout(500);

PDU pdu = new PDU();
pdu.setType(PDU.GET);

OID oid = new OID("1.3.6.1.2.1.1.");
VariableBinding vb = new VariableBinding(oid);

pdu.add(vb);
...
...

snmp.send(pdu, target);

So the last line, snmp.send(pdu, target), will return the SNMP4j Response having the value for OID we set in the PDU.This is just the example of how to get any data from OID.We can set the values using SET PDU.

Batch insert/update DB - Use XML as you data...

2008-11-25T23:03:00.000+05:30

Today we have many strange requirements because of latest developments in the IT market. We are having tons of data to be inserted in databases or files etc.Mainly for DB operation, we can use batch insert/update, which calls DB for multiple rows of params.

This is not an excellent thing, but i think you should take care of this.Just think that if you are having 100 rows to be inserted in one table, and you make batch update call from you java code.How much time and resources it will take?We just can't answer this question.Yeah, we can't but we have different solution here.

Instead of making batch params data, you make and XML data using XSLT transformation or Castor mapping.We will see what these both things mean later. Today every Database server supports XML parameters as an input to Stored procedure/Function.You can pass your XML to the SP, and then handle the XML traversal logic inside the SP.You are done!

You just need to,

1.Create the XML data for Input param.
2.Pass the XML,execute the SP.
3.SP will handle the XML data and do the processing fetching the data from XML(Using Xpath traversal)
4.SP also can return resultset data as an XML content, which you can again transform map to Object.

XML Transformation: is done by javax.xml.Transform package, which takes one XML as input,Used XSLT file to transform input XML to XML format as defined by the XSLT.

Castor Mapping:is done by third party open source jar, which maps Object to XML and XML to object.So you can directly get XML/Object using this.

Remote Method call - EJB/HTTPClient/Web Service?

2008-07-14T10:58:00.000+05:30

This is not a new thing i am talking about,but i have used this for first time. Until now i have been used to EJB for remote method invocations. I use it for some bussiness logic which is on another distributed server. And i am not ashamed of telling that i have not used Web services :(.

This was a need in my project to call a method of another application which can be on same machine or another. First i thought i need to call a EJB and its all mess because of heavy loads for a simple method call. But when i saw the implementation, i got confused how i will cuse it! But my senior told me to check using HTTPClient from apache commons.

Its very simple to call a method on servlet using HTTPClient. Check the code below. We will just use PostMethod class for parameters to be passed and execute the request. So as per the parameters,the servlet will do its work.

PostMethod postMethod = new PostMethod("http://some.blah.com");
postMethod.setParameter("some_id", "1");
postMethod.setParameter("param1", "any data");
postMethod.setParameter("param2", "any data");
...
int status = httpClient.executeMethod(postMethod); //status will be your response...

Its so simple. But though its not a call which returns something. I mean you cna see i am just passign some information to some method to invoke some processing which is independent and i don't need its response.

Controlling Module Dependencies in Eclipse

2008-05-20T12:42:00.000+05:30

J2EE Module Dependencies is a critical issue in an enterprise application. You need your one web module to access some resources while prohibiting others. Similar is the case with EJB modules.

Let’s figure it out with Eclipse Web Tools Platform. I consider that you all have ability to create projects and modules in Eclipse; so skipping those steps. I have Eclipse 3.3 with WTP 2.0 M6.

I have created project with following details.

MyProject – Enterprise project

MyEJB_Module – Contains bean class

MyEJBClient_Module – Contains interfaces of EJB, VO, and BeanUtil.

MyWeb_Modules – Holds JSPs, servlets and all presentation tier stuffs.

MyJava_Module – Contains common classeslike constants, utilities.

Starting with MyProject, select properties from right click menu. In property dialog, select “J2EE Module Dependencies”. You will find all the modules. Select all as project is dependent on all modules.

Now you can configure dependency of individual module, let’s take an example of web module. In “J2EE Module Dependencies” window, you will find a radio button group which would has by default “Use EJB Client Jars” option selected. That radio button groups defines visibility of EJB jar.

As clients of any EJB should be isolated from bean classes, it is preferable not to select other options where you can define dependencies with EJB jar file. After all, EJB clients should not have any kind of dependencies with EJB jar.

Now here if I select MyEJB_ModuleClient.jar only, MyWeb_Module won’t able to access classes defined in MyJava_Module until you redefine module dependencies.

Similarity you can define dependencies with Utility project, specifically saying third party libraries. You want one module to access one jar and isolate others all you need to do is add library in main project (MyProject in my case) and then configure dependencies of other modules.

This feature takes care of dependencies on behalf of you and let you concentrate on other tasks.

Servicemix PollingComponentSupport - stuck if lower period and higher threadPoolSize

2008-05-15T15:35:00.000+05:30

Again i got one issue with servicemix Poller components.

We have two FilePoller components here and we kept the period to 10 minutes. Which means the instance of FilePoller will run at every 10 minutes. Now say if I have two instances, each run at 10 minutes, and 5 minutes gap between them. So it means after every five minutes, files will be picked by one of them. And the WorkManager, which is given to FilePoller as property, has threadPoolSize of 30.

All was working fine with this configuration.30 threads in pool, every five minutes any of two pullers will pick files. But now we have to change it. When we changed the period from 10 minutes to 1 minute, we got strange errors. Yes even you won't believe it. While testing concurrency we got, FileNotFound exception even though the file exists there, and many other concurrency issues. We looked into the logs and found that sometimes the load goes only on one server and the other is always idle doing nothing. Because when it comes, the first one is doing task.

Then we decided to decrease the thredPoolSize. Becasue if puller get 30 files for 30 threads from the pool, and when it comes to 31st file from the folder and if any of previous 30 threads is in the pool after it has completed its job, then it will take the file. It means, though we have pool size of 30, it may be possible that it can process more than 30 files per instance (say 32 to 38 files). So we decided to make pool size to 10.

Now after making 10 it seems to be working fine. Each one is picking almost equal numbers of files and sharing load as it should. Let’s see if more issues are coming or not.

So, key thing to be remembered is

"Keep you threadPoolSize and period on which instance will run in proportion to each other. If period is long then threads can be more but if you want to reduce the period, you must take care of pool size."

Java optimization and performance

2008-05-13T11:47:00.000+05:30

No new Exception if not needed

Many of us do this when we want to throw an error. But if you are throwing exception from another catch, then don't make new exception object. Keep throwing the same exception which you caught if possible. This will be better for performance. And also in new exception usually we change the description only to reflect the perfect error cause, but other ways are there to track it.

Avoid excessive synchronization

Yah threading can be a bit complex situation sometimes in java. And we all use synchronization to avoid dead locks. But it needs a more attention then we give it. Try to make a block of code synchronized rather then making the whole method synched. The whole method will stop all other threads, waiting to go inside it. It will generate more overhead. So keep the design like we need less sync code.

Release DB and File IO

This is the most case in which we all do something wrong.
DB connections must be closed after completing your DB transactions because its a limited resource.

Also if you are using File IO, then must close file streams after completing the task.

Best way for this is, to write the releasing code in 'finally' block of the method.

Use StringBuffer/StringBuilder rather than String

We use string manipulations in our daily coding many times. And all we do is always making new String object. As most of us know, String is immutable object (which means once assigned you can't change its value), so when you assign existing String object another value, it will make new String object. And most string operation generates lot of small String objects.

If it’s possible to use StringBuffer or StringBuilder instead of String then its more more way better. Because it will be one object having all your data in it and you can get String form it when you want.

Now StringBuilder is nonSynchronized and StringBuffer is synchronized. So if you don't have threading issues and don't need Sync, then you must use StringBuilder which is included since jdk 1.5.

Later on we will talk about more points also when i remember them :)

servicemix problems: NormalizedMessage getContent,copyPropertiesAndAttachments()

2008-05-09T17:07:00.000+05:30

Though servicemix is widely used and very nice ESB framework, it has some basic problems.The one i am talking about here is very little thing but it can be annoying if you forget this or don't know this.

While creating and sending NormalizedMessage object from any data, after doing that if you read data using NormalizedMessage.getContent() method and send the message object with exhchange to deliveryChannel, using DeliveryChannelImpl.send(MessageExchange) method, then you will get null exception in DeliveryChannelImpl class.

Yes this is true.I don't know why, but it removes content from the message object.Only the content is removed and the properties are still there.

You can read properties from it in same component as many times as you want.If you are forwarding same message to next component, properties will automatically goes.But if you read content once, you must set it again :(.

Also remember that if you need to make new MessageExchange, then you must copy all properties and attachments using TransformComponentSupport.copyPropertiesAndAttachments(outExchange,inMsg,outMsg) method.Then all your data from one message will be copied to another message.

So keep checking this if you getting null Exceptions while sending message through DeliveryChannel.

Spring Framework problem : SqlReturnResultSet() not returned

2008-05-09T17:06:00.000+05:30

One more problem with servicemix and spring is in DAO classes, when you make any private static class of StoreProcedure, then in its constructor you must declare SqlReturnResultSet before you declare SqlParameter.Otherwise you will not be able to find return data from StoredProcedure execution.Check the code below,

public MySp(JdbcTemplate jdbcTemplate){
super(jdbcTemplate,"sp_mysp");
declareParameter(new SqlReturnResultSet("strRs",rsMyResultSet));
declareParameter(new SqlReturnResultSet("strRs1",rsMyResultSet1));
declareParameter(new SqlParameter("myId", Types.INTEGER));
compile();
}

so keep in mind while using Spring DAO support.Must declare resultsets first.

Using Struts tags - ,,

2008-05-01T19:07:00.000+05:30

I was wondering what should i write about now.And suddenly i got this to do.
I have a small change in the jsp which is made using struts framework.In struts, there are many tags which are easy to use and generate output fast.easy to write.

In struts, we have ActionServlet,Action classes and ActionForms.

ActionServlet will transfer the request to ActionServlet with ActionForms containing all the HTML form data.so you can access any data of the of ActionForm from Servlet request.

See the below code.then we will talk regarding it.

<select name="sel1" id="selTestStruts" style="width:90px;">
<option value="0" selected="selected">Please Select
<logic:iterate id="myBean" name="someForm" property="someFormProp1">
<logic:equal value="test" property="someStrPropOfMyBean" name="myBean">
<option value='<bean:write name="myBean" property="someStrPropOfMyBean"/>'><bean:write name="myBean" property="someNamePropOfMyBean"/></option>
</logic:equal>
</logic:iterate>
</select>

here we are trying to fill HTML select box using struts' <logic:iterate>, <logic:equal><bean:write> tags.

<logic:iterate> will iterate on 'someFormProp1' of 'someForm' which is in the http request.it will make 'myBean' from property 'someFormProp1' which is a List of some data.

You can simply write any property from that 'myBean' we made above.But i also shown here how you can put logic to seperate things on some property value so you don't need to put logic in the SP or generate another property for it.

<logic:equal> checks the value of property named 'someStrPropOfMyBean' with the string given in 'value="test"' attribute (means with 'test' here). If the value matches then only it will make new <option> for <select> box.

same thing you can do with not including some specific value match using <logic:notEqual>

<bean:write> tag will simply write property 'someStrPropOfMyBean' of 'myBean' which is a object of some Value Object class from the List property 'someFormProp1' of 'someForm'.

Though this is very simple thing but i write because may be this can be helpful to some newbies.

Castor Xml mapping: mapping.loadMapping() gives IOException for filepath

2008-04-25T10:58:00.000+05:30

This is very know problem i think and many of you know it but then also i am writing it here.

For convert a Value Object class directly in pre-defined XML format we use castor mapping.We give xml mapping file (as we have seen in earlier tutorial) to Mapping class object as below which will write xml string in strWriter object from Object obj.

Mapping mapping = new Mapping();
mapping.loadMapping(mappingXmlFilename);
strWriter = new StringWriter();
Marshaller marshaller = new Marshaller(strWriter);
marshaller.setMapping(mapping);
marshaller.marshal(obj);

But when i given directly the filename to loadMapping method, it gives IOException as below:

IOException : \shared\p1\p2\shared\p1\p2\lai-sup-mapping.xml

i have given absolute filepath '\\shared\p1\p2\lai-sup-mapping.xml' and then also it is generating it using relative one.So throwing IOException for file.

Then i have changed the thing and instead of giving filepath, i have made a org.xml.sax.InputSource object from the xml file and passed that xml source to loadMapping() as below:

Mapping mapping = new Mapping();
InputSourcemappingSource =
newInputSource(new FileInputStream(mappingXmlFilename));
mapping.loadMapping(mappingSource);
strWriter = new StringWriter();
Marshaller marshaller = new Marshaller(strWriter);
marshaller.setMapping(mapping);
marshaller.marshal(obj);

And its working fine.Now its generating correct XML file from the given Value object.

Servicemix Queue filled - Queue size increased

2008-04-24T15:07:00.000+05:30

I have been using servicemix since more then 1 year.As we have seen in urlier articles that servicemix uses ActiveMQ for Message queuing. The messages sent are filled in the Queue of destined component which will be fetched later on.

When we started using Servicemix, we faced a strange problem.After running for sometimes,our application stops processing messages.When we looked in the JMS Queue, we found that after certain period the messages in the queue are not removing.So new messages can't be processed.The Queue is full and we must restart the application to get rid of this.

Then we dig into the source code of servicemix and found how queue is given size.We increased the size as per our need and the problem was solved.

Basically when message processed by the component, it will be removed from its queue.But for some reason, if message not processed or not removed from the queue then further messages will be stored in the queue and processing stops.The application seems to be running but messages are not processed.

The class org.apache.servicemix.jbi.util.BoundedLinkedQueue contains the property capacity_
Constructor of this class contains the magic which initializes the capacity of queue size.

By default it is 1024.you can change it as per your need. I mean how much messages you think will be processed after every restart.

code:

public BoundedLinkedQueue() {
this(1024);
}
public BoundedLinkedQueue(int capacity) {
if (capacity <= 0)
throw new IllegalArgumentException();
capacity_ = capacity;
putSidePutPermits_ = capacity;
head_ = new LinkedNode(null);
last_ = head_;
}

I just simply changes the 1024 to bigger number like 1024*10 etc...

Try this.may be it can solve your problem also.

And others who know about servicemix and want to share their problems and tweaks are welcome.Put your comments here i will post it.

Java Web application cookie lost!

2008-04-24T11:04:00.000+05:30

I got one new change to do in our java web application.I have not been in it since 2 or 4 months and forgot some of its settings.

First of all my jboss refuses to run from eclipse!i was very worried about it, but later i re-configured it as a "dynamic web application" project in eclipse.

So when jboss runs finally, i logged in it and a big blast! it redirected me to error page. I checked the logs but i can't find anything.I was thinking that even i have not chnaged the things in code,configuration etc. then also it stucks here?

But suddenly, a spark happned and i remembered that we set domain for cookies in most web applications.And that thing sucks in local environment.
cookie setting code:

Cookie c1 = new Cookie(name, value);
c1.setDomain(domainName);

So i just commented out c1.setDomain(domainName); and my application is ok.

Java Mail API with Encoded Attachment FileNames

2008-04-21T16:17:00.000+05:30

This is very strange problem i faces as per me. May be because different email clients have different encodings or something else, but we will get encoded filename header from some email clients like lotus, blackberry phone etc.

Message header for attachment:

Content-Transfer-Encoding: base64
Content-Type: image/jpeg
Content-Disposition:attachment;
filename="=?Windows-1252?B?SU1HMDAwMTYuanBn?="

Then i was stucked with the thing that how to decode the filename.I have the filename only in subject line.But i can not trust that because say if 3 attachments are there, then there will be 3 filenames in subject in order.But we should not depend on the subject of the email.

javax.mail.internet.MimeUtility util class which helps to decode the encoded strings in message header values as below

Method:

javax.mail.internet.MimeUtility.decodeText(strValueToBeDecoded);

But most of the encodings with java 1.3.1 are not supported. At least 1.4.1 must be used.

Eclipse Shortcuts

2008-04-11T16:22:00.000+05:30

I was free as my code with CR is done. i was thinking wht to write and it just sparked in my mind that this can be a good thing though many of us has explored this.But then also it can help some newbies.

Maximize/minimize the selected window - Ctrl +M
Generate getters/setter - Alt+Shift+s + r
Override/implement methods - Alt+Shift+s + v
Show type implementation - Ctrl+T on selected type in java file
quick class member browser - Ctrl+o
search usage of selected member - Ctrl+Alt+H
comment/uncomment selected lines - ctrl+/
Open declaration - F3

This is what most used ones. You also can submit if i missed important ones in commnets.

Using Apache ServiceMix - ESB with spring

2008-04-11T15:52:00.000+05:30

Apache ServiceMix is an open source ESB (Enterprise Service Bus) that combines the functionality of a Service Oriented Architecture (SOA) and an Event Driven Architecture (EDA) to create an agile, enterprise ESB.

Apache ServiceMix is an open source distributed ESB built from the ground up on the Java Business Integration (JBI) specification JSR 208 and released under the Apache license. The goal of JBI is to allow components and services to be integrated in a vendor independent way, allowing users and vendors to plug and play.

Features:

ServiceMix is lightweight and easily embeddable, has integrated Spring support and can be run at the edge of the network (inside a client or server), as a standalone ESB provider or as a service within another ESB. You can use ServiceMix in Java SE or a Java EE application server.

ServiceMix uses ActiveMQ to provide remoting, clustering, reliability and distributed failover.

ServiceMix is completely integrated into Apache Geronimo, which allows you to deploy JBI components and services directly into Geronimo. ServiceMix is being JBI certified as part of the Geronimo project.

Other J2EE application servers ServiceMix has been integrated with include JBoss, JOnAS with more to follow.

ServiceMix includes a complete JBI container supporting all parts of the JBI specification including:

* Normalized Message Service and Router
* JBI Management MBeans
* Ant Tasks for management and installation of components
* full support for the JBI deployment units with hot-deployment of JBI components

ServiceMix also provides a simple to use Client API for working with JBI components and services.

How to use?

JBI components can be created extending servicemix's implementation classes.This is required because only then can you will be able to use the plug-&-play component,which is our purpose to use servicemix ESB.

You can develop Binding components which can receive data through HTTP and Files.Servicemix has already provided specific classes so you can deal with http request,input folder.

HTTP - org.apache.servicemix.components.http.HttpConnector.
File - org.apache.servicemix.components.file.FilePoller

So your class will use the HTTP request/file to fetch data and will make an javax.jbi.messaging.NormalizedMessage class object.

This NormalizedMessage object will be then given to javax.jbi.messaging.MessageExchange implementation (InOnly or InOut) and MessageExchange will be then routed to the next component configured as service endpoint in application context xml file.

application context xml code:

<sm:activationSpec componentName="myfilePoller" service="foo:myfilePoller" destinationService="foo:myDrool">
<sm:component>
<bean class="test.my.file.MyFilePoller">
<property name="workManager" ref="workManager" />
<property name="file" value="C:/inbox" />
<property name="period" value="120000" />
<property name="deleteFile" value="true" />
</bean>
</sm:component>
</sm:activationSpec>

<sm:activationSpec componentName="myDrool" service="foo:myDrool">
<sm:component>
<bean class="org.apache.servicemix.components.drools.DroolsComponent">
<property name="ruleBaseResource" value="classpath:myRule1.xml" />
</bean>
</sm:component>
</sm:activationSpec>

Here MyFilePoller is the class which will poll files from 'C:/inbox' folder. And make messaging as we discussed above.'myDrool' is its destination component which is an drools component.

Drools is like dynamic routing.We just need to make rules in xml file and that xml will be loaded automtically if its configured in applicationContext file as above. Its jar must be in 'lib' dir of the server.

Below is the drools xml which declares the rule base on which the NormalizedMessage will be routed to appropriate destination component.

NormalizedMessage can contain data and properties.We can read its property in XML rule base.And based on particular property, we can route the message.

Check the xml below.

myRule1.xml:

<rule-set name="cheese rules"
xmlns="http://drools.org/rules"
xmlns:java="http://drools.org/semantics/java">
<application-data identifier="jbi">org.apache.servicemix.components.drools.JbiHelper</application-data>
<application-data identifier="context">javax.jbi.component.ComponentContext</application-data>
<application-data identifier="deliveryChannel">javax.jbi.messaging.DeliveryChannel</application-data>
<rule name="Rule for componentOne">
<parameter identifier="exchange">
<class>javax.jbi.messaging.MessageExchange</class>
</parameter>
<java:condition>"TRUE".equalsIgnoreCase(exchange.getMessage("in").getProperty("isForComponentOne").toString()) == true</java:condition>
<java:consequence>
jbi.forwardToService("http://servicemix.apache.org/demo/", "componentOne");
</java:consequence>
</rule>
<rule name="Rule for anotherComponent">
<parameter identifier="exchange">
<class>javax.jbi.messaging.MessageExchange</class>
</parameter>
<java:condition>"TRUE".equalsIgnoreCase(exchange.getMessage("in").getProperty("isForComponentOne").toString()) == false</java:condition>
<java:consequence>
jbi.forwardToService("http://servicemix.apache.org/demo/", "anotherComponent");
</java:consequence>
</rule>
</rule-set>

This will route the message to 'componentOne' if the property tested in condition is true and toward 'anotherComponent' otherwise.Both components also will be specified in applicationcontext xml file.

This is how routing does work.Now we will talk about how each component get notified of message transfered.

Every intemediate component in servicemix will create new message and Exchange,pass it to next component after finishing its processing and send notification to the previous component.

code:

getDeliveryChannel().send(newExchange);
done(exchange);

At last, we now talk about the service endpoint, which has opposite task compared to binding components.

BindingComponents takes in and creates messages, Service endpoints throw out the messages and finishes the process.

we have 3 to 4 different outbidding components here and its having some classes already provided.

File - org.apache.servicemix.components.file.FileWriter
FTP - org.apache.servicemix.components.net.FTPSender
HTTP - org.apache.servicemix.components.util.OutBinding ( i have used this becasue in http, we will jsut send data to some URL or so and then processing is finished.)
Mail/SMTP - org.apache.servicemix.components.email.MimeMailSender

This is how we can use servicemix. You can add different components as per your needs at any place in the whole flow and define the path in xml applicationContext and Rule base files.

The changes or additions afterward will require some small changes only. You need to define new properties in NormalizedMessage and based on that property you can create new RuleBase files. And using drools, create new routing path for new feature.

Its very easy to use though feels very tricky and complex in the beggining.

we Will discuss more. :)

Developement Processes: Some Important some boring

2008-04-11T11:05:00.000+05:30

This is no new thing i am writing about.All developers know this and gone through this when ever they got some new thing to develop. It hurts in heart when someone says something which you must do as a process and feels boring.

As per SDLC, some basic steps needed for developers are,

Reading specs and use cases

This is most annoying thing i ever found. Yes because what the analysis team does all knows. Copy-paste some basic paragraphs from the templates,making funny and ugly diagram in word which is never usable to developers,using fast vivid colors which will just make you cry or feels you are reading some horror story and finally the language which is too complex and contains thing which are not of use! What they mention you can't get and what you want them to know they can't deal with it!

Deciding approach & Making design diagrams

This is somewhat very important thing if the team is well. Otherwise all are just suggesting diff. approaches and no decisions at the end!Design diagrams must be prepared before the development but sometimes the project managers or the CEOs are in so hurry that they want get it done fast and deployed even without any Technical documents/design diagrams!
Sometimes the coder submits the diagrams and docs for review but the leaders/seniors are so busy (or may be ignoring it thinking 'its not related to my project') and not reviewed it.And after the code is done, they will find holes and design problems in that.Now say who's fault is this?
This is cool when its a small thing and approach is simple, but when you are expecting a whole big feature/module/functionality in short period ,with testing yes keep this in mind "with testing" done,then its a hell for developer. After the coding done, developer asked for diagrams. Now say, isn't its boring? Yes that what i am saying. It sucks!

Coding

Its best part if the thing is designed and design is reviewed properly.As per my experience this is the least time taking step for a good team.

Code Review

CR must be done. But if its done in quite short time after the code done. it means, CR should be fast process of all because developer can complete task fast if its in period while he is inside the thing.Once he had given for CR and you get back to him after some 1 month or so then he even doesn't remember what he had done!
And at some places, quite boring procedures for CR. you submit code filenames for CR, distribute it to some person,write comments on it and etc... This is time wasting and it stinks! It must be a simple process like pressing a button because developers' time is not for this funny things.

Deployment

This may be complex thing but it should not waste coders time. But at some places, system people stuck and call for coders.Some are intelligent to get into but some are even not understanding on total help and documentation provided by a coder.Only the instructions needed to be given by a coder.Its not his job to deploy the whole titanic into the sea!

Testing

Now is the worst thing that a developer may be need to do sometimes.Yes i have done this even more than hundreds times because of some funny and frustrating test cycles! Sometimes they even don't know how to test & What should they do!You can say its better you do it all instead giving them the idea.This is mostly happens because nowadays testing people are nontechnical! They just know clicking the button and etc.They don't know how to deal with application internals and view log and all.May be companies wants some nontechnical arts graduate as a tester in less money instead of a good testing software engineer!
And sometimes they raise wrong bugs which have been tested with wrong scenarios,even on your instructions that this is not right one to test!And when you draft a mail which makes them shy or some senior person bang on them, they feels you like an enemy!

Bug fixing

This is most 'long long long' process for coders.The diff. natured(technical/nontechnical,thinking themselves as coders) testers rais long list of bugs out which rare cases are function issues.Most are like for UI things.And when a coder is given a bug which not of his area then definitely it will consume more time and if we calculate total time for such non-related-area bugs of all coders then it will make a big difference in the process completion date.May be it can delay release if the testing cycles are more in numbers but less detailed and proper.

This is not like i am bored of coding. I love coding but everything which is having its charms,have some bad things also associated with it.Say if testers are also coders then? may be you can get more bugs? yes but you can test fats and at the end your final release would be a great thing.Same thing applies for all team in SDLC ;). i mean analysis,project management,testing all.

I am telling what i think. It depends on particular's likings ;)

Just do Code.

Relo - Relationship based Exploration (UML Like Diagrams)

2008-04-04T22:41:00.000+05:30

Relo helps developers explore and understand large codebases. Developers often face code that is hard to understand with over half their time being spent on understanding code. Relo allows developers to easily create relevant and intuitive diagrams, along with features to help automatically build diagrams based on the users past navigation.

While Relo diagrams are similar to UML, they also allow developers to zoom in to view details and edit the code using embedded text editors. These diagrams represent only a small manageable part of the code and do not include irrelevant details, thus allowing a developer to focus on important code relationships.

Relo HomePage

Java - Javascript interaction

2008-04-04T22:38:00.000+05:30

Many of us using javascript in daily coding.I am a java developer and using ajax with applet also.And i need to call applet methods from javascript.

Actually i knew this while i was facing a strange problem (ofcourse it was strange for me becasue i was not aware of this!). The applet used is compiled in JRE 1.4.0.And whenever anyone having JRE version newer than 1.4.0 tried accessing that applet, the call from javascript to applet method gives error "Object doesn't support this property". So i was very much tired of compiling applet with different versions of Jre but no luck.

So once i found the <param> tags for <Object> element which is now used for applet in HTML code.And then i used these tags for java and javascript interaction.

we will look at what parameters we should use the applet and object tags to 'switch on' the java-js communications.

According to the java 5 documentation, if you use the APPLET tag, you do not need any special parameters to allow a javascript to call the applet's method. On the other hand if you use the OBJECT tag you need to use the scriptable parameter. Things use to be slightly different in the older versions.

For an applet to call javascript methods, all you need to do is add the mayscript parameter

so the tags are

<object classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93"
width= "290" height= "290" style="border-width:0;" id="rup" name="rup"
codebase="http://java.sun.com/products/plugin/autodl/
jinstall-1_4_1-windows-i586.cab#version=1,4,1">
<param name="archive" value="jsapplet.jar">
<param name="code" value="com.raditha.articles.JSHelloWorld">
<param name="mayscript" value="yes">
<param name="scriptable" value="true">
<param name="name" value="jssapplet">
</object>

The object tag can actually cause the most recent version of the java plug in to be downloaded if the user does not have it installed or if the version present is older than the minimum requirement (in this case 1.4.1). If you want to be able to do the same for Netscape Navigator the object tag has to change slightly:

<object classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93"
width= "290" height= "290" style="border-width:0;" id="rup" name="rup"
codebase="http://java.sun.com/products/plugin/autodl/
jinstall-1_4_1-windows-i586.cab#version=1,4,1">
<param name="archive" value="jsapplet.jar">
<param name="code" value="com.raditha.articles.JSHelloWorld">
<param name="mayscript" value="yes">
<param name="scriptable" value="true">
<param name="name" value="jsapplet">
</object>

Calling applet method from javascript is simple. You just need to do document.getElementById("appletid").methodName();
But calling javascript from Applet is somewhat tricky.

In order to call javascripts we need to get hold of a JSObject. But first things first, we need to import the netscape.javascript.JSObject into our class.

public void init()
{
jsObj= JSObject.getWindow(this);
}

All that remains to do is to add the JButton to our applet. Then we add an ActionListener to the JButton, and it's actionPerformed method calls the javascript.

public void actionPerformed(ActionEvent e) {
if(jsObj != null )
try {
jsObj.call("updatePage", new String[] {txt.getText()});
}
catch (Exception ex) {
ex.printStackTrace();
}
}

thats it! it will call the method from jsObj.

hope this helps someone like me for first time.Enjoy!

Java Spring Framework : Multiple PropertyPlaceholderConfigurer configurtion

2008-04-04T22:33:00.000+05:30

This is very small thing which can be very annoying while coding in spring framework. Of cource no one can directly understand the problem until he faced that.

At first, I had only one property file from which i am reading some values into spring applicationContext Xml configuration file.So when i needed to add second one for my new feature, i think it is just to add new propertyPlaceholderConfigurer bean with second prop file.

my first prop file 'default-prop.properties' is :

default-prop.custName=testing customer
default-prop.address=building1

and the bean definition in the applicationContext xml file for this is:

<bean id="propertyConfigurer"
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="location">
<value>classpath:default-prop.properties</value>
</property>
</bean>

so while adding second one, i have just added second bean for it like:

<bean id="propertyConfigurerNew"
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="location">
<value>classpath:second-prop.properties</value>
</property>
</bean>

and in xml, prop has been read as,

<property name="customerName" value="${default-prop.custName}" />

But when i done this, i got error

"Could not resolve placeholder 'default-prop.custName' "

So i have to do some workaround and digg into spring references. And i found that we can define seperate placeHolderPrefix and suffix for each property configurer bean.

I have changed the bean definition as,

<bean id="propertyConfigurer"
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="location">
<value>classpath:default-prop.properties</value>
</property>
<property name="placeholderPrefix" value="${" />
<property name="placeholderSuffix" value="}" />
</bean>

<bean id="propertyConfigurerNew"
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="location">
<value>classpath:second-prop.properties</value>
</property>
<property name="placeholderPrefix" value="#[" />
<property name="placeholderSuffix" value="]" />
</bean>

it means, for first prop bean, we will use ${default-prop.custName} and for second bean we will use #[second-prop.secondName]

And voila! it solved my problem...

You can also use

<property name="ignoreUnresolvablePlaceholders" value="true" />

for each PropertyPlaceholderConfigurer bean defined. But, i have used the prefix-suffix one solution.
And my problem is resolved.

Give your comments on this problem and solution.