Explanation of the @Interceptor Annotation

Ahoy there, ye scurvy dogs! Today, we be diving into the deep waters of CDI and exploring the mysterious @Interceptor annotation. This here annotation be a powerful tool for ye to modify the behavior of yer code by intercepting method invocations. So grab yer spyglass and let’s set sail!

How the @Interceptor Annotation is Used to Specify an Interceptor Class

Now, imagine ye be a pirate with a trusty parrot on yer shoulder. Whenever ye be talking, the parrot be repeating everything ye say. But what if ye could intercept the parrot’s speech and modify it before it reached the ears of yer mateys? That’s where the @Interceptor annotation comes in handy.

In CDI, an interceptor is a class that can intercept method invocations of other beans. By adding the @Interceptor annotation to a class, ye be telling CDI that it be an interceptor class. Ye can then specify which methods ye want to intercept by adding the @AroundInvoke annotation to the method.

Here be an example to help ye understand better:

@Interceptor
public class PirateInterceptor {
    @AroundInvoke
    public Object intercept(InvocationContext context) throws Exception {
        System.out.println("Avast! Ye be calling a method on " + context.getMethod().getName());
        Object result = context.proceed();
        System.out.println("Shiver me timbers! The method " + context.getMethod().getName() + " be done!");
        return result;
    }
}

In this example, we’ve created an interceptor class called PirateInterceptor. It has a single method called intercept that intercepts the method invocations of other beans. The method takes an InvocationContext object as a parameter, which provides information about the intercepted method.

Inside the intercept method, we be printing a message before and after the method invocation, then calling the context.proceed() method to proceed with the original method invocation. Finally, we be returning the result of the method invocation.

Now, let’s use this interceptor to intercept the method invocations of a bean:

@Stateless
public class ShipService {
    @Inject
    EntityManager em;
    
    @Interceptors(PirateInterceptor.class)
    public void sailTheSevenSeas() {
        System.out.println("Setting sail!");
    }
}

In this example, we’ve created a ShipService bean that has a method called sailTheSevenSeas. We’ve added the @Interceptors(PirateInterceptor.class) annotation to the method, which tells CDI to use the PirateInterceptor class to intercept method invocations of this method.

Now, when we call the sailTheSevenSeas method, the PirateInterceptor intercepts the method invocation and prints a message before and after the method invocation. Ye can use interceptors to add additional functionality to yer code without changing the original code.

Conclusion

Well, me hearties, that be all for today’s adventure into the world of CDI and the @Interceptor annotation. Ye can now use interceptors to modify the behavior of yer code by intercepting method invocations. Just remember to use them wisely and avoid the Kraken! Until next time, happy coding!