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

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...

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...

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...

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...

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.