https://github.com/spring-projects/spring-framework: Spring AOP (Spring IO)
  • Juergen Hoeller 
/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.aopalliance.intercept;


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;
  }
}



Author:Rod Johnson
/**
 * Intercepts calls on an interface on its way to the target. These
 * are nested "on top" of the target.
 *
 * <p>The user should implement the {@link #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)):
 *
 * <pre class=code>
 * 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;
 *   }
 * }
 * </pre>
 *
 * @author Rod Johnson
 */
@FunctionalInterface
public interface MethodInterceptor extends Interceptor {

	
Implement this method to perform extra treatments before and after the invocation. Polite implementations would certainly like to invoke Joinpoint.proceed(). 
Params:
  • invocation – the method invocation joinpoint
Throws:
  • Throwable – if the interceptors or the target object
throws an exception
Returns:the result of the call to Joinpoint.proceed(); might be intercepted by the interceptor
/**
	 * Implement this method to perform extra treatments before and
	 * after the invocation. Polite implementations would certainly
	 * like to invoke {@link Joinpoint#proceed()}.
	 * @param invocation the method invocation joinpoint
	 * @return the result of the call to {@link Joinpoint#proceed()};
	 * might be intercepted by the interceptor
	 * @throws Throwable if the interceptors or the target object
	 * throws an exception
	 */
	Object invoke(MethodInvocation invocation) throws Throwable;

}