How Do You Use an EJB in Your Application?

Interceptor Restrictions

You can use interceptors with:

• stateless session beans

• stateful session beans

• message driven beans

OC4J applies an interceptor to all business methods of a bean.

In this release, you must define an interceptor as a method of the bean class to which it applies. You may define only one interceptor method per class.

An interceptor method may not be a business method.

An interceptor method has the following signature:

public Object <METHOD>(InvocationContext) throws Exception

Within an interceptor, you can use the InvocationContext to access client invocation metadata (see "Interceptors and Invocation Context").

An interceptor must observe the following transaction restrictions:

• Interceptor method invocations occur within the same transaction and security context as the business method for which they are invoked.

• Interceptor methods can mark their transaction for rollback by throwing a runtime exception or by calling setRollbackOnly using its EJBContext object as follows:

  InvocationContext.getEJBContext().setRollbackOnly();
  
  

  Interceptors may cause this rollback before or after they call InvocationContext.proceed().

  For more information, see "Using a Rollback Strategy".

• When using container-managed transactions (see "Container-Managed Transaction (CMT)"), interceptors must not use any resource-manager specific transaction management methods that would interfere with the container's demarcation of transaction boundaries. For example, the interceptor must not use the following methods of the java.sql.Connection interface: commit, setAutoCommit, and rollback; or the following methods of the javax.jms.Session interface: commit and rollback. Interceptors must not attempt to obtain or use the javax.transaction.UserTransaction interface.

Interceptors and Invocation Context

Using the InvocationContext API, you can access (and modify) all the metadata relevant to the client invocation and implement fine grained control over method invocation flow by selectively choosing whether or not to allow the client invocation to proceed. Using EJB 3.0 interceptors, you can:

• Modify parameters before they're passed to the bean

• Modify the value returned from the bean

• Catch and swallow method exceptions

• Interrupt the call completely (for example, to implement your own security framework)

• Provide method profiling