Enterprise JavaBeans 3.1, 6th Edition

Interceptors and Injection

Interceptors belong to the same ENC as the EJBs they intercept. Like the EJBs they intercept, interceptor classes have full support for all the injection annotations, as well as injection through XML. So, you can use annotations such as @Resource, @EJB, and @PersistenceContext within your interceptor class if you so desire. Let’s illustrate this in a revised view of our auditing interceptor:

public class RecordingAuditor
{

   ...

   /**
    * The current EJB Context; to be injected by the Container
    */
   @Resource
   EJBContext beanContext;

   /**
    * Persistently records the intercepted {@link InvocationContext} such that
    * we may examine it later
    */
   @AroundInvoke
   public Object audit(final InvocationContext invocationContext) throws Exception
   {
      // Precondition checks
      assert invocationContext != null : "Context was not specified";

      // Obtain the caller
      final Principal caller = beanContext.getCallerPrincipal();

      // Create a new view
      final AuditedInvocation audit =
         new AuditedInvocation(invocationContext, caller);

      // Record the invocation
      invocations.add(audit);

      ... // The rest omitted for brevity

   }

}

The purpose of this interceptor is to log in a persistent view every method invocation done on a particular bean so that an audit trail is created. From this audit trail, system administrators can research security breaches or replay the actions of a particular user. The interceptor obtains the calling user by invoking getCallerPrincipal() on the javax.ejb.EJBContext injected into ...