Killer Game Programming in Java

Packaging the Application as a JAR

I'm converting the ImagesTests application into a JAR so all the resources (images, in this case) are packaged with the code in a single file. This makes the application easier to transport, and I get the additional benefit of compression.

Tip

I won't consider how to use applets and JAR together or advanced topics, like signing and manipulating JARs from inside Java code. The Java tutorial (trail) on JARs should be consulted on these matters.

Before JARing begins, it's important to organize the resources in relation to the application. The ImagesTests code is located in the directory ImagesTests/ (see Figure 6-21), which acts as the top-level directory for the JAR. The images are placed in an Images/ subdirectory within ImagesTests/. This makes their inclusion into the JAR easy.

One issue with using Windows is that it displays filenames in a user-friendly lowercase format. Unfortunately, Java is less forgiving, and will be unable to find a file such as BASN6A08.PNG if told to load basn6a08.png. The application developer should open a DOS window and check the filenames in Images/ directly.

The next step is to create a text file, which will become the basis of the manifest inside the JAR file. The manifest holds a range of meta-information about the JAR, related to matters like authentication, extensions, and sealing. However, I'll only add the name of the top-level class, ImagesTests, which contains the main() method. This permits the application to ...