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Summary of Transaction Options for Enterprise Beans

If you're unsure about how to set up transactions in an enterprise bean, here's a tip: In the bean's deployment descriptor, specify container-managed transactions. Then set the Required transaction attribute for the entire bean. This approach will work most of the time.

Table 30-2 lists the types of transactions that are allowed for the different types of enterprise beans. An entity bean must use container-managed transactions. With container-managed transactions, you specify the transaction attributes in the deployment descriptor and you roll back a transaction by calling the setRollbackOnly method of the EJBContext interface or when a system-level exception is thrown.

Table 30-2 Allowed Transaction Types for Enterprise Beans

Bean Type	Container-Managed	Bean-Managed
		JTA	JDBC
Entity	Y	N	N
Session	Y	Y	Y
Message-driven	Y	Y	Y

A session bean can have either container-managed or bean-managed transactions. There are two types of bean-managed transactions: JDBC and JTA transactions. You delimit JDBC transactions using the commit and rollback methods of the Connection interface. To demarcate JTA transactions, you invoke the begin, commit, and rollback methods of the UserTransaction interface.

In a session bean with bean-managed transactions, it is possible to mix JDBC and JTA transactions. This practice is not recommended, however, because it can make your code difficult to debug and maintain.

Like a session bean, a message-driven bean can have either container-managed or bean-managed transactions.

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