ConstructorInterceptor

Intercepts the construction of a new object.

The user should implement the method to modify the original behavior. E.g. the following class implements a singleton interceptor (allows only one unique instance for the intercepted class):

 class DebuggingInterceptor implements ConstructorInterceptor { Object instance=null; Object construct(ConstructorInvocation i) throws Throwable { if(instance==null) { return instance=i.proceed(); } else { throw new Exception("singleton does not allow multiple instance"); } } } 

Invocation

This interface represents an invocation in the program.

An invocation is a joinpoint and can be intercepted by an interceptor.

MethodInterceptor

Intercepts calls on an interface on its way to the target. These are nested "on top" of the target.

The user should implement the #invoke(MethodInvocation) method to modify the original behavior. E.g. the following class implements a tracing interceptor (traces all the calls on the intercepted method(s)):

 class TracingInterceptor implements MethodInterceptor { Object invoke(MethodInvocation i) throws Throwable { System.out.println("method "+i.getMethod()+" is called on "+ i.getThis()+" with args "+i.getArguments()); Object ret=i.proceed(); System.out.println("method "+i.getMethod()+" returns "+ret); return ret; } } 

MethodInvocation

Description of an invocation to a method, given to an interceptor upon method-call.

A method invocation is a joinpoint and can be intercepted by a method interceptor.