At this point, we have said just about all
that can be said about the bean itself. We have come to the end of
<enterprise-beans> element and 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
<ejb-jar> element: the
<assembly-descriptor> element is
optional, though it is difficult to imagine a bean being deployed
successfully without an
<assembly-descriptor>. When we say that the
<assembly-descriptor> 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> element 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 ...