Java Reference
In-Depth Information
Creating interceptors
There is one more CDI feature worth mentioning here, the interceptors. Sometimes, ap-
plications contain logic and cross-cutting multiple layers; the most simple example is log-
ging. Under the Java EE platform, it can be achieved using interceptors. First, we need to
create a new annotation:
@Inherited
@InterceptorBinding [1]
@Retention(RetentionPolicy.RUNTIME)
@Target({ ElementType.METHOD, ElementType.TYPE })
public @interface Logged {
// empty
}
This annotation defines an interceptor binding. It can be used to specify methods that you
would like to intercept. The bindings can be used on types as well; in that case, every
method call on that type is intercepted. The most important part of this definition is the
@InterceptorBinding [1]
annotation. Be sure to add it!
Then, we have to create the interceptor definition itself:
@Interceptor
@Logged [1]
public class LoggingInterceptor implements
Serializable
{
@AroundInvoke [2]
public Object log(InvocationContext context) throws
Exception {
final Logger logger =
Logger.getLogger(context.getTarget().getClass());
logger.infov("Executing method {0}",
context.getMethod().toString());
return
context.proceed() [3];
}
}
We start by stating that our class is
@Interceptor
and it will be using the interceptor
binding that we've defined earlier (
@Logged [1]
). Next, we create a method log that
