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:
<ejb-jar> ... other elements ... </ejb-jar>
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 the 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 EJB deployment descriptor doesn’t use a<description>element for the deployment descriptor as a whole, but it does provide a description for the Cabin EJB itself.-
<display-name>(optional) The
<display-name>element is used by tools (such as 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 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 x 16 pixels; large icons must be 32 x 32 pixels. These icon elements are also used in the
<entity>,<session>, and<message-driven>(EJB 2.0) elements to represent individual enterprise bean components.-
<enterprise-beans>(one required) The
<enterprise-beans>element contains descriptions of one or more enterprise beans that are contained in this JAR file. A deployment descriptor may have only one<enterprise-beans>element. Within this element,<entity>,<session>, and<message-driven>(EJB 2.0) elements describe the individual beans.-
<ejb-client-jar>(optional) The
<ejb-client-jar>element provides the path of the client JAR, which normally contains all the classes (including stubs, remote and home interface classes, etc.) the client will need in order 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 enterprise 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 transaction attributes.
These elements are quite simple, with the exception of the
<enterprise-beans> and
<assembly-descriptor> elements. These two
elements contain a lot of other material nested within them.
We’ll look at the <enterprise-beans>
element first.