Beginning Java EE 6 with GlassFish 3, Second Edition

CHAPTER 8 ■ CALLBACKS AND INTERCEPTORSLife-Cycle InterceptorIn the first part of this chapter, you learned how to handle callback events in your EJB. With a callbackannotation, you can inform the container to invoke a method at a certain life-cycle phase(@PostConstruct, @PrePassivate, @PostActivate, and @PreDestroy). For example, if you want to log anentry each time a bean instance is created, you just need to add a @PostConstruct annotation on onemethod of your bean and add some logging mechanisms to it. But what if you need to capture life-cycleevents across many types of beans? Life-cycle interceptors allow you to isolate some code into a classand invoke it when a life-cycle event is triggered.Life-cycle interceptors really look like what you’ve just seen in Listing 8-4. Instead of @AroundInvoke,methods can be annotated with callback annotations. Listing 8-6 shows the ProfileInterceptor classwith two methods: logMethod(), used for postconstruction, and profile(), used for predestruction.Listing 8-6. A Life-Cycle Interceptor Defining Two Methodspublic class ProfileInterceptor {private Logger logger = Logger.getLogger("com.apress.javaee6");@PostConstructpublic void logMethod(InvocationContext ic) {logger.entering(ic.getTarget().toString(), ic.getMethod().getName());try {return ic.proceed();} finally {logger.exiting(ic.getTarget().toString(), ic.getMethod().getName());}}@PreDestroypublic void profile(InvocationContext ic) {long initTime = System.currentTimeMillis();try {return ic.proceed();} finally {long diffTime = System.currentTimeMillis() - initTime;logger.fine(ic.getMethod() + " took " + diffTime + " millis");}}}As you can see in Listing 8-6, life-cycle interceptor methods take an InvocationContext parameter,return void instead of Object (because life-cycle callback methods return void, as explained earlier in the“Callbacks” section), and cannot throw checked exceptions.To apply the interceptor defined in Listing 8-6, the session bean needs to use the @Interceptorsannotation. As you can see in Listing 8-7, CustomerEJB defines the ProfileInterceptor. When the EJB isinstantiated by the container, the logMethod() of the interceptor will be invoked prior to the init()method. Then, if a client calls createCustomer() or findCustomerById(), no interception will happen.But, before CustomerEJB is destroyed by the container, the profile() method will be invoked.249