Associating an interceptor class with the target class

The @AroundInvoke annotation establishes the operations that an interceptor executes when the bean is intercepted. Here is a sample of an annotated operation for an interceptor:

@AroundInvoke
public Object aroundInvoke(InvocationContext ic) throws Exception {
      String methodName = ic.getMethod().getName();
      return ic.proceed();
}

To associate this interceptor to a bean, create a qualifier annotation:

@Retention(RUNTIME)
@Target({ METHOD, TYPE, CONSTRUCTOR })
@InterceptorBinding
public @interface Audit {
}

Add it on to the interceptor to identify the interceptor:

@Interceptor
@Audit
public class AuditInterceptor {
...}

And, at the end, add the qualifier in the method or field of the bean you want intercept:

@Audit
public List<Item> getList() {
     return items;
}

Now when the getList() method is invoked, automatically the method of the Interceptor marked as @AroundInvoke is invoked.

In the case of Timeout method interceptors, the interceptor applies to all Timeout methods of the target class:

@AroundTimeout
public Object aroundTimeout(InvocationContext ic) throws Exception {
    Object[] parameters = (Object[]) ic.getParameters();
    return ic.proceed();
}

To execute this method of the interceptor, we need a bean marked as EJB working with the time service. It will be seen in detail in Chapter 4, Implementing Business logic.

A new invocation method of the interceptor introduced in Java EE 7 is the invocation through constructor:

@AroundConstruct
public Object aroundConstruct(InvocationContext ic) throws Exception {
     Map<String, Object> data = ic.getContextData();
     data.forEach((k, v) -> logger.info("data key: " + k + " - value: " + v));
     return ic.proceed();
}

To start it, simply add the qualifier annotation in a constructor of a bean:

public class ItemServiceBean ...{
   @Audit
   public ItemServiceBean() {
     items = new ArrayList<Item>();
   }
...
}

We can exclude the invocation of class-level interceptors through the ExcludedInterceptors.class annotation or through deployment descriptors different by beans.xml. An example of a descriptor is the ejb-jar.xml that lets us exclude default and class interceptors.

Here's a sample of exclusion of class interceptors through annotation:

@interceptors({ ExcludedInterceptor.class, IncludedInterceptor.class })
public class SimpleService {
     private Item item;
     @ExcludeClassInterceptors
     public Item getItem() {
          return item;
     }
     public void setItem(Item item) {
          this.item = item;
     }
}

The getItem method will never be intercepted by ExcludedInterceptor and IncludedInterceptor, while setItem will be intercepted by both.