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10.4. The Descriptor's Body

The body of any XML document begins and ends with the tag for the document's "root element," which is defined by the DTD. For a deployment descriptor, the root element is named ejb-jar, and looks like this:

... other elements ...

All other elements must be nested within the ejb-jar element. You can place the following kinds of elements within ejb-jar:

<description> (optional)

The description element can be used to provide a description of this deployment descriptor. This element can be used in many contexts within a deployment descriptor: to describe the descriptor as a whole, to describe particular beans, to describe particular security roles, etc. The Cabin bean deployment descriptor doesn't use a description element for the deployment descriptor as a whole, but it does provide a description for the Cabin bean itself.

<display-name> (optional)

The display-name element is used by tools (like a deployment wizard) that are working with the deployment descriptor. It provides a convenient visual label for the entire JAR file and individual bean components.

<small-icon> and <large-icon> (optional)

These elements point to files within the JAR file that provide icons that a deployment wizard or some other tool can use to represent the JAR file. Icons must be image files in either the JPEG or GIF format. Small icons must be 16 × 16 pixels; large icons must be 32 × 32 pixels. These icon elements are also used in the entity and session elements to represent individual bean components.

<enterprise-beans> (one required)

The enterprise-beans element contains descriptions of the bean or beans that are contained in this JAR file. A deployment descriptor must have one, and only one, enterprise-beans element. Within this element, entity and session elements describe the individual beans.

<ejb-client-jar> (optional)

The ejb-client-jar provides the path of the client JAR, which normally contains all the classes (including stubs, remote and home interface classes, etc.) that the client will need to access the beans defined in the deployment descriptor. How client JAR files are organized and delivered to the client is not specified--consult your vendor's documentation.

<assembly-descriptor> (optional)

The application assembler or bean developer adds an assembly-descriptor element to the deployment descriptor to define how the beans are used in an actual application. The assembly-descriptor contains a number of elements that define the security roles used to access the bean, the method permissions that govern which roles can call different methods, and transactional attributes.

All of these elements are quite simple, except for the enterprise-beans element and the assembly-descriptor element. These two elements contain a lot of other material nested within them. We'll look at the enterprise-beans element first.

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