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Java Developer : Article

How to Create a Simple Java J2ME Application for BlackBerry

With WebSphere Studio Device Developer

Having employees constantly connected to one's enterprise is vital to many companies. This is one of the reasons Research in Motion's BlackBerry has mustered a massive following (over three million users at the time of this article's writing) in recent years. BlackBerry addiction has become pandemic. In this article, you'll learn how to build, test, and deploy applications to Blackberry devices using WebSphere Studio Developer.

WebSphere Studio Device Developer (hereafter called Device Developer) provides you with an integrated development environment (IDE) in which you can build, test, and deploy J2ME applications.

For learning purposes, the sample MIDlet application you'll create following the steps in this article is pretty simple: it takes input text from a user, transposes the text, then displays the transposed text to the user. For example, if a user enters the text IBM, the transposed, or mirrored, text MBI is returned.

The BlackBerry Java development environment (JDE), which runs only on Windows operating systems, consists of an IDE and BlackBerry emulator tools that let you see exactly how the J2ME application you build will work on a BlackBerry device. In this article, we'll use the Device Developer IDE rather than the IDE that ships with the BlackBerry JDE. However, you still need to download and install the BlackBerry JDE in order to use the BlackBerry emulation environment. This way, you can see how your J2ME application will act on the actual BlackBerry device. See Resources for information on downloading the BlackBerry JDE.

You also need to have the following software installed:

  • Java 2 SDK, Standard Edition V5.0
  • WebSphere Studio Device Developer. Device Developer is part of the IBM WorkSpace Client Technology, Micro Edition 5.7 Integrated Package. Check out Resources for information on downloading a trial version of Device Developer.
You should have a basic knowledge of Eclipse and the BlackBerry JDE.

Create the application
First, we need to create our MIDlet application using Device Developer. We'll put our MIDlet in a MIDlet suite.

1.  Create a new MIDlet Suite project, then click Next, as shown in Figure 1:

2.  On the MIDlet Suite Creation screen, do the following:

  1. Enter MirrorMidlet for the MIDlet name.
  2. In the Midlet Suite Name field, type MirrorMidletSuite.
  3. Select 2.0 for the MIDP Version.
  4. Enter Mirror Midlet
  5. Enter a MIDlet class Package of com.ibm.test and a Name of MirrorMidlet, then click Next.
Figure 2. Create MIDlet Suite

3.  Select the default J9 JVM ive-2.2, and click Finish.

Figure 3. Select JVM

4.  The MIDP Visual Editor is launched. Since we won't be using the visual editor in this article, you can go ahead and close it.

5.  At this point our MIDlet is pretty barebones. We need to edit it to make it perform the transposition function described earlier. To do this, right-click MirrorMidlet.java and select Open with => Java Editor.

6.  Replace the existing class definition with the following:

public class MirrorMidlet extends MIDlet implements
      {protected Form form;
      protected TextField input = new
TextField("String:", null, 128, TextField.ANY);
      Command commandConvert = new Command("Convert", Command.OK, 1);

7.  Add the following to protected void startApp():

// Init form

8.  Add the following method:

public void commandAction(Command aCommand, Displayable aDisplayable)
{ if (aCommand == commandConvert){char aChar;
      int size = input.size();
      char[] charArray = new char[size];

      // determine inverse
      for (int i = 0; i < size / 2; i++){aChar = charArray[i];
      charArray[i] = charArray[size-1-i];
      charArray[size-1-i] = aChar;

      // update screen
      input.setChars(charArray, 0, size);

9.  The code above implements the transposition function. The core of the transposition logic lies in the if clause of the commandAction method, which simply transposes the letters of an input character array using a for loop.

10.  Now build the project by right-clicking on the MirrorMidlet project and selecting Build Project.

Create the Java Application Descriptor (JAD) and JAR files
Now that the code is complete, you need to create a JAR file and associated JAD file for deploying to the J2ME device. To do this, you need to set up a build by completing the following steps:

  1. Right-click on the MirrorMidlet project and select Device Developer Builds.
  2. . Select Add to create a new build.
  3. Click Next on the Create generic JAR window. (Figure 4)
  4. Select Generic JAR in the Create new build window, and click Finish. (Figure 5)
  5. In the Configure Builds window, select Run to build the JAD and JAR files, which are located in the generic/folder. (Figure 6)
  6. Optional: If you have any images or other resources associated with your project, complete the following steps to include them:
    1. Edit generic/MirrorMidletSuite.jexlinkOptions, and select the Source tab.
    2. Add the location of the folder containing the additional resources using -cp.
    3. To include the resources specify includeResource "*.xxx" (for example, *.png), as shown in Figure 7.
Debug the application
Before deploying the application to your BlackBerry, you can use the Device Developer IDE's built-in debugger to debug your J2ME application by completing the following steps:
  1. Set a breakpoint within the project, as shown in Figure 8:
  2. Select Run => Debug, then select MirrorMidlet Suite, then New to create a new debug profile.
  3. Select the default JRE of ive-2.2 and MirrorMidletSuite.jad.
  4. Click Debug to begin debugging your MIDlet. (Figure 9)
Deploy the application
You now have a JAR file that is ready to be deployed to a J2ME device. Unfortunately, we can't just deploy this JAR file to a BlackBerry. First, we have to convert the JAR file to the BlackBerry .cod format. To do this, complete the steps below:
  1. Create a jartocod.bat file to use with the Blackberry JDE, as shown:

    @ECHO "Syntax: jartocod.bat JAD_NAME JAR_NAME OUTPUT_NAME"
    @"C:\Program Files\Research In Motion\BlackBerry JDE 4.1.0\bin\rapc
    "import="C:\Program Files\Research In Motion\BlackBerry JDE
    4.1.0\lib\net_rim_api.jar" codename=%3 -midlet jad=%1 %2

  2. Copy the JAD and JAR files you created earlier from the generic/ folder to the location of the jartocod.bat.
  3. Type the command: jartocod.bat MirrorMidletSuite.jad MirrorMidletSuite.jar MirrorMidlet.
Now you have a .cod file that the BlackBerry can understand.

Deploy to the BlackBerry simulator

  1. Launch the BlackBerry Device Simulator by selecting Start => Research In Motion => BlackBerry JDE => Device Simulator.
  2. Once the simulator is loaded, install the .cod file by selecting File => Load Java Program. (Figure 10)
  3. Navigate to the directory containing your .cod file and open the file. (Figure 11)
  4. Locate the icon on the BlackBerry Simulator desktop and launch it. Hint: The up and down arrows function as Select and Back emulated BlackBerry buttons. (Figure 12)
  5. Select the Transpose function from the context menu to see the Mirror MIDlet work on the BlackBerry simulator. (Figure 13)
Deploy to a Real BlackBerry
Deploying your .cod file to a real BlackBerry device is a pretty simple operation:
  1. First, create an installcod.bat file to use with the Blackberry JDE, as shown below:

    @ECHO "Syntax: installcod.bat COD_NAME.cod"

    @"C:\Program Files\Research In Motion\BlackBerry JDE
    4.1.0\bin\javaloader" -u load %1

  2. Next, plug your BlackBerry device into your computer using a USB cable and execute the installcod.bat batch file to install the MIDlet onto the BlackBerry device.
In this article, you learned how to use the power of IBM WebSphere Device Developer to build and test J2ME applications and then deploy them to the BlackBerry platform. The J2ME application we created in this article didn't need to interact across the network to perform its function. In our next article, we'll show you how to create a more complex BlackBerry application using Device Developer that involves invoking of a Web service on WebSphere Application Server.

(This article appeared originally online at IBM Developer Works.)

More Stories By Kulvir Singh Bhogal

Kulvir Singh Bhogal works as an IBM Software Services for WebSphere consultant, devising and implementing WebSphere-centric solutions at customer sites across the nation. He has over fifty patents pending in a myriad of technology areas. He can be reached at [email protected]

More Stories By Michael Masterson

Michael Masterson is a results driven technology executive with 12 years of experience in Social, Mobile, and Enterprise Software. He currently leads business development and strategy for Compuware APM with a focus on Big Data and Cloud. Previously he held product management, strategy, and engineering roles at IBM. He has a passion for product, perseverance to build channel ecosystems, and focuses on execution. Reach him at @mlmasterson

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