February 2004
Intermediate to advanced
848 pages
27h 25m
English
Content preview from WebLogic: The Definitive GuideBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Using J2EE Services on the Object Tier
The object tier usually maps to a WebLogic cluster that houses the heavier J2EE services such as EJB and RMI objects, as well as the JMS resources. Because the EJB objects typically need JDBC access to the backend DBMS (data tier), the object tier in our multi-tier application setup also hosts the JDBC resources. Remember, a clustered architecture need not have an object tier. If your application doesn’t use EJBs to encapsulate the business logic or doesn’t require any asynchronous message handling, you easily can bypass the object tier. In that case, you could deploy the JDBC resources to the presentation tier directly.
Even if your application does make use of EJB objects and/or JMS resources, you still need not construct a separate object tier cluster. You could deploy your entire application (servlets, JSPs, EJBs, JMS destinations, etc.) to a single WebLogic cluster. We examine the trade-offs of this combined-tier architecture later in this chapter.
This section examines the object tier by first exploring the interplay between replica-aware stubs and WebLogic’s clustered JNDI service. Then we review how EJB and RMI objects, JDBC, and JMS resources behave in a clustered environment.
Interacting with the Object Tier
Establishing the object tier cluster is
no different from setting up the web/presentation tier. The object
tier cluster, named OCluster here, is composed of
two Managed Servers, ServerF and
ServerG. Both servers coexist on another ...
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