Describing Bean Assembly
At this point, we have said just
about all that can be said about the bean itself. We are now ready to
describe how the beans are assembled into an application. That is, we
are ready to talk about the other major element inside the
<ejb-jar> element: the
element is optional, though it is
difficult to imagine a bean being deployed successfully without one.
When we say that the
is optional, we really mean that a developer whose only role is to
create enterprise beans (for example, someone who is developing beans
for use by another party and who has no role in deploying the beans)
can omit this part of the deployment descriptor. The descriptor is
valid without it—but someone will almost certainly have to fill
in the assembly information before the bean can be deployed.
<assembly-descriptor> serves three
purposes: it describes the transaction attributes of the
bean’s methods; it describes the logical security
roles that are used in the method permissions; and it specifies the
method permissions (i.e., which roles are allowed to call each of the
methods). To this end, an
<assembly-descriptor> can contain three
kinds of elements, each of which is fairly complex in its own right.
<container-transaction>(zero or more)
This element declares which transaction attributes apply to which methods. It contains an optional
<description>element, one or more
<method>elements, and exactly ...