It seems like an eternity since I last tried J2ME or JavaME as its known now. It was Sept 2003, when I was working at a product development company and was building a component using J2ME. I even managed to get an article published at http://my.advisor.com/articles.nsf/aid/12697.

When I tinkered with Android a few weeks back, I got the urge right then to revisit JavaME. I wanted to try out a JavaME example again and see if anything has changed. I still believe that JavaME will eventually die out in favor of a more full featured platform (whether it is Java SDK or something else I dunno). For a primer on JavaME stacks you can check my article on advisor above. It surprising how little has changed.

In this example I will build a JavaME application using Netbeans. The application will present the user with a screen to enter a ISBN number for a book. It will then make a remote web service call to validate that the ISBN number is valid or not. When I tried a similar webservice example in 2003, web services was not yet in the optional stack. Now it is. Previously I was using ksoap. Now I do not need to. I can use the built-in libraries (if the device supports that... and that is the big headache with either JavaME or Android....device capabilities).

Create a new NetBeans MIDP project named as ISBNValidator, using CLDC-1.1 and MIDP-2.1 configuration. The IDE will create a ISBNValidatorMidlet. Netbeans will throw you into a page flow designer. I switched to the source code view.  Change the code to:


package com.test;

import isbnservice.ISBNService_Stub;
import java.rmi.RemoteException;

import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;

public class ISBNValidator extends MIDlet implements CommandListener {

    private EnterISBNNumberForm isbnForm;

    public ISBNValidator() {
        isbnForm = new EnterISBNNumberForm("ISBN Validator", this);
    }

    protected void destroyApp(boolean arg0) {
    }

    protected void pauseApp() {
    }

    protected void startApp() throws MIDletStateChangeException {
        Display.getDisplay(this).setCurrent(isbnForm);
    }

    public void commandAction(Command cmd, Displayable disp) {
        if (cmd.getCommandType() == Command.EXIT) {
            destroyApp(false);
            notifyDestroyed();
        } else if (cmd.getLabel().equalsIgnoreCase("Check ISBN")) {
            final MIDlet parent = this;
            new Thread() {

                public void run() {
                    String result = validateISBN(isbnForm.getIsbnNumber());
                    String msg = "ISBN Validd => " + isbnForm.getIsbnNumber() + ", is ";
                    ISBNValidatorResultForm resultForm = new ISBNValidatorResultForm(msg, result, (CommandListener) parent);
                    Display.getDisplay(parent).setCurrent(resultForm);
                }
            }.start();
        } else if (cmd.getLabel().equalsIgnoreCase("Main")) {
            Display.getDisplay(this).setCurrent(isbnForm);
        }
    }

    private String validateISBN(String isbn) {
        ISBNService_Stub stub = new ISBNService_Stub();
        String result = "bad isbn";
        if (isbn == null || (isbn.trim().length() != 10 && isbn.trim().length() != 13)) {
            return result;
        }
        try {
            if (isbn.trim().length() == 10 && stub.IsValidISBN10(isbn)) {
                result = "good isbn";
            } else if (isbn.trim().length() == 13 && stub.IsValidISBN13(isbn)) {
                result = "good isbn";
            }
        } catch (RemoteException e) {
            e.printStackTrace();
        }
        return result;
    }
}

In the method validateISBN you can see I do the web service call. Now you must be guessing how I got the stubs created. Netbeans has made that easy for us. Right click on the project and select "New JavaME Web Service Client". Provide the WSDL URL webservices.daehosting.com/services/isbnservice.wso?WSDL and you are done.

For sake of completeness here are the other 2 classes I coded. I put the forms in two independent classes.

Class EnterISBNNumberForm
package com.test;

import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Form;
import javax.microedition.lcdui.TextField;

public class EnterISBNNumberForm extends Form {

    private Command okCommand;
    private Command exitCommand;
    private TextField isbnNumber;

    public EnterISBNNumberForm(String title, CommandListener cmdlistener) {
        super(title);

        exitCommand = new Command("Exit", Command.EXIT, 1);
        okCommand = new Command("Check ISBN", Command.OK, 1);

        isbnNumber = new TextField("ISBN#: ", "", 13, TextField.ANY);
        append(isbnNumber);
        addCommand(okCommand);
        addCommand(exitCommand);
        this.setCommandListener(cmdlistener);
    }

    public String getIsbnNumber() {
        return isbnNumber.getString();
    }
}


Class ISBNValidatorResultForm
package com.test;
import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Form;
import javax.microedition.lcdui.StringItem;

public class ISBNValidatorResultForm extends Form {
    private Command okCommand;
    private StringItem box;
    private String value;

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }

    public ISBNValidatorResultForm(String title, String value,
            CommandListener cmdlistener) {
        super(title);
        this.value = value;
        okCommand = new Command("Main", Command.OK, 1);
        box = new StringItem("ISBN Valid => ", this.value);
        append(box);
        addCommand(okCommand);
        this.setCommandListener(cmdlistener);
    }

}

If you run the project an emulator should pop up and you can launch the application. Following two images show the application in action: