Enterprise JavaBeans, Third Edition

Declarative Transaction Management

One of the primary advantages of Enterprise JavaBeans is that it allows for declarative transaction management. Without this feature, transactions must be controlled using explicit transaction demarcation. This involves the use of fairly complex APIs like the OMG’s Object Transaction Service (OTS) or its Java implementation, the Java Transaction Service ( JTS). Explicit demarcation is difficult for developers to use at best, particularly if you are new to transactional systems. In addition, explicit transaction demarcation requires that the transactional code be written within the business logic, which reduces the clarity of the code and, more importantly, creates inflexible distributed objects. Once transaction demarcation is hardcoded into the business object, changes in transaction behavior require changes to the business logic itself. We talk more about explicit transaction management and EJB later in this chapter.

With declarative transaction management, the transactional behavior of EJBs can be controlled using the deployment descriptor, which sets transaction attributes for individual enterprise bean methods. This means that the transactional behavior of an EJB can be changed without changing the EJB’s business logic. In addition, an EJB deployed in one application can be defined with different transactional behavior than the same EJB deployed in a different application. Declarative transaction management reduces the complexity of transactions ...