Part II - Web service client programs

Please note that due to the current funding situation, the NGS no longer supports a Web Service interface to its resources. We have kept this tutorial online in case it is of use for users of other Grids.

In this part, we're going to work with the client programs only. The server is already up and running at a NeSC host (This is no longer available, to use this practical, set up your own GT4 server following the Part III of this practical first). There're five client programs that match required functionality.

Here are the files:

• gtwitter
  
  • src
    
    • Register.java
    • Login.java
    • Update.java
    • Lister.java
    • Follow.java
    • Streams.java
    • ClientBase.java - this is the base class to do all interfacing work.

1. Register

The first program, Register.java, is ready to compile and run, let's do it: (you can use any username and password, but keep it)

cd ~/gtwitter

ant compile-client

ant register -Duser=<your_username> -Dpass=<your_password>

If you wonder how this works, you can read the source code in Register.java and especialy ClientBase.java. The createService method contains the essential steps to connect to the remote service and obtain a resource and the service port type.

2. Login

The Login.java is left blank for you to fill in, otherwise it does nothing. Open this file in an editor, select and copy the following code block into where appropriate:

public String login(String username, String password) throws Exception 	{
           LoginInput ri = new LoginInput(); 
            ri.setUsername(username); 
            ri.setPasscode(password); 
            return this.service.login(ri);
 	} 

Save the source file, and compile and run it:

ant compile-client

ant login -Duser=<your_username> -Dpass=<your_password>

3. Update

This can be done in the same way as Login, but it's up to you to figure out what method to call this time. You can find it out from the port type stub file:

~/gtwitter/build/stubs/src/uk/ac/nesc/toe/gtwitter/stubs/Instance/GTwitterPortType.java

In this class, you can find there's a method as:

public java.lang.String update(java.lang.String param) throws java.rmi.RemoteException;

It means the update method accepts a String argument and returns a String as well. The argument is the status text to update.

Now compile and run:

ant update -Dstatus="any text you want to give"

You can add more text, but each text must be limited to no more than 140 characters long as Twitter.

4. Streams

This program will fetch what you have written on the gTwitter microblog and display.

Modify the code in the same way, then compile and run:

ant streams

5. List

Now most of you may have registered, and let's try to find out who they are. Again, edit file Lister.java, and find out how to call the service.

Modify, compile and run:

ant list

6. Follow

We have several friends on gTwitter already, so let's follow them so that we can get what they put on their microblogs.

ant follow -Duser=<username_2_follow>

You can follow more people, one each time.

7. Finally

Now let's see our streams again, and this time, you'll see also the posts by those we are following.

ant streams