Enterprise JavaBeans, Second Edition

Improved Performance with Session Beans

In addition to defining the interactions among entity beans and other resources (workflow), session beans have another substantial benefit: they improve performance. The performance gains from using session beans are related to the concept of granularity. Granularity describes the scope of a business component, or how much business territory the component covers. As you learned previously, very fine-grained dependent business objects are usually modeled as pass-by-value objects. At a small granularity, you are dealing with entity beans like Ship or Cabin. These have a scope limited to a single concept and can only impact the data associated with that concept. Session beans represent large, coarse-grained components with a scope that covers several business concepts—all the business concepts or processes that the bean needs in order to accomplish a task. In distributed business computing, you rely on fine-grained components like entity beans to ensure simple, uniform, reusable, and safe access to data. Coarse-grained business components like session beans capture the interactions of entities or business processes that span multiple entities so that they can be reused; in doing so, they also improve performance on both the client and the server. As a rule of thumb, client applications should do most of their work with coarse-grained components like session beans, and with limited direct interaction with entity beans.

To understand how session ...