Skip to main content Link Menu Expand (external link) Document Search Copy Copied

How to Use CDI Interceptors

Header Image

Welcome aboard, mateys! Today, we’re going to talk about CDI interceptors and how to use them in your Java applications. As you know, CDI (Contexts and Dependency Injection) is a powerful framework that allows you to create loosely coupled and highly modular applications. With interceptors, you can take that modularity to the next level by intercepting method invocations and modifying their behavior.

Using the @Interceptor Annotation

So, what exactly is an interceptor? Well, an interceptor is a class that intercepts method invocations and can modify the method’s behavior. This can be useful for things like logging, performance monitoring, and security checks. In CDI, you can specify an interceptor class using the @Interceptor annotation.

To create an interceptor, you first need to define a class with the behavior you want to intercept. Let’s say you want to log the start and end of every method invocation in a particular class. Here’s an example of what that interceptor class might look like:

@Interceptor
public class LoggingInterceptor {

    @AroundInvoke
    public Object logMethodInvocation(InvocationContext context) throws Exception {
        System.out.println("Starting method: " + context.getMethod().getName());
        Object result = context.proceed();
        System.out.println("Ending method: " + context.getMethod().getName());
        return result;
    }

}

In this example, we’ve defined an interceptor class called LoggingInterceptor. The class is annotated with @Interceptor, which tells CDI that this class is an interceptor. The class also has a method called logMethodInvocation that will be called every time a method is intercepted.

The logMethodInvocation method is annotated with @AroundInvoke, which tells CDI that this method should be called around the intercepted method. The InvocationContext parameter gives you access to information about the intercepted method, such as its name, parameters, and return type. In this case, we’re simply logging the start and end of the method invocation and then proceeding with the method as normal.

To use the LoggingInterceptor, you simply need to apply it to the class or method you want to intercept using the @Interceptors annotation. Here’s an example of how to apply the interceptor to a class:

@Interceptors(LoggingInterceptor.class)
public class MyClass {
    // ...
}

In this example, we’re applying the LoggingInterceptor to the MyClass class. Now, every time a method in MyClass is called, the logMethodInvocation method in the LoggingInterceptor will be called before and after the method is executed.

And there you have it, me hearties! Using the @Interceptor annotation, you can easily create interceptors that modify the behavior of your methods. Whether you’re logging, monitoring performance, or checking security, interceptors are a powerful tool in your arsenal.

Conclusion

Thanks for sailing with us today as we explored the exciting world of CDI interceptors. We hope this article has been informative and entertaining. Remember to use the @Interceptor annotation to specify an interceptor class, and you’ll be well on your way to creating highly modular and flexible applications. Until next time, fair winds and following seas!