About Java Application Descriptor (JAD) Files

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Every MIDlet suite file is accompanied by a Java Application Descriptor ( ) file. This file contains a predefined set of attributes that allow the application management software ( ) to identify, retrieve, and install the MIDlets. The JAD file enables the application management software on a mobile device to verify that the MIDlet is suited to the device before loading the full JAR file of the MIDlet suite. The descriptor also supplies configuration-specific attributes (parameters) to the MIDlet or MIDlets without modifying the JAR file.

In the IDE, the JAD file is created automatically when you create a MIDlet suite. The contents of the application descriptor file can be viewed and edited by choosing File and choosing "Project name" Properties, then selecting Application Descriptor.

The following attributes are required in a JAD file:

Other attributes are available for use, depending on the version of MIDP supported by the project configuration:

User-defined attributes in the JAD file can provide the AMS with additional information about a MIDlet that, for example, might help the AMS determine whether the application can be run on the target device.

Another use for user-defined attributes is that they can help a MIDlet dynamically adapt itself to different target devices. As a result, the same JAR file can support a variety of devices without being modified.

For example, you might add the attributes Display-Width = 160 and Display-Height = 120 to the JAD, which defines the display area of the target device.

Each user-defined attribute must have a unique name. Attribute names cannot start with MIDlet-, and cannot contain spaces.

See Also
Customizing the Application Descriptor File

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