Java Reference
In-Depth Information
that type, the relation will no longer validate. In this case, the relation service
will remove the relation from the group of registered relations. The relation ser-
vice is “aware” of the relations and the MBeans that correspond to the roles and
ensures that the integrity of the relations remains intact.
The service also acts as the source of notifications, providing information about
the relations it contains. If a relation is created, updated, or deleted, the relation
service will send a notification containing information about the modification.
11.1.1
Components of the relation service
In the previous section, we introduced some new terms: relation , relation type , and
role . These terms correspond to some of the classes that make up the relation ser-
vice. Throughout this chapter, we will use these terms and their classes to describe
the relation service and construct examples. Therefore, you need to have a good
understanding of these and other terms. This section will help you round out
your knowledge of the following terms:
Relation service
Relation type
Role information
Relation
Role
The relation service is a complex agent service. When you're working through
the examples in this chapter, you can come back to this section to refresh your
knowledge of these terms. Likewise, the relation framework being described may
be difficult to envision. As you work through the example step by step, these con-
cepts should become clearer.
Relation service
The relation service is an MBean that defines the methods used to create and
remove relation types and relations. In addition, the relation service provides
methods for finding a particular relation.
The relation service lets you create internal and external relations. Internal
relations are relations that exist only within the relation service MBean. This
type of relation only provides information about the MBeans that create a rela-
tionship. In contrast, external relations are registered with the relation service,
but also exist as MBeans registered in the agent. In this chapter, you will create
an external relation. This type of relation has some unique advantages that we
will expose shortly.
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