J2ME : A complete HTTP Client

From TechnologicalWiki

This article shows how to create a Hello World example for a MIDlet. The client receives a Hello World Message from the server.

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.io.*;
import java.io.*;

public class HTTPHelloWorld extends MIDlet implements CommandListener, Runnable {

    private Alert alert;
    private Command exit,connect;
    private Display screen;
    private Form main;
    private TextField ftext;

    public HTTPHelloWorld() {

          /* this is the main screen of the MIDlet*/
          main = new Form("HTTP Connection");
          ftext=new TextField("Readed Text:","",30,TextField.ANY);
          connect = new Command("Connect",Command.SCREEN,0);
          exit = new Command("Exit",Command.EXIT,0);
          main.append(ftext);
          /* command to connect to the server */
          main.addCommand(connect);
          main.append(exit);
          main.setCommandListener(this);
    }

    /* This method is called at the beginning of the execution (MIDlet)*/
    public void startApp() {

          screen = Dispaly.getDisplay(this);
          screen.setCurrent(principal);
          ftext.setString("Push connect ... ");
    }

    /* MIDlet method */
    public void pauseApp() {};

    /* MIDlet method */
    public void destroyApp( boolean unconditional ) {}


    public commandAction(Command command, Displayable screenable) {

          if (command == exit) {
              destroyApp(true);
              notifyDestroyed();
          } else if (command == connect) {

              /* when connect is the connect pushed, the connection thread will be thrown */
              Thread t = new Thread(this);
              t.start();
          }
    }
    public void connect() {

          HttpConnection connection = null;
          InputStream input = null;
          int length;
          byte[] text;
          String str;
          try {

               ftext.setString("Connecting...");
               connection = (HttpConnection) Connector.open("http://mysever/helloWorld.php");

               ftext.setString("Opening...");
               input = connection.openInputStream();

               length = ( int ) connection.getLength();
               if ( length == - 1){
                    length = 255;
               }

               text = new byte[length];
               ftext.setString("Reading...");
               length = input.read(text);
               input.close();
               connection.close();
               str = new String(text,0,length);
               ftext.setString(str);

          }  catch ( Exception error ) {

               /* an error has occurred */
               alert = new Alert("Error Connecting",error.toString(),null,AlertType.WARNING);
               alert.setTimeout(Alert.FOREVER);
               screen.setCurrent(alert);
          }
    }
    public void run() {

        connect();

    }
}