Spring AOP配置与管理的补充—环绕通知

 Spring AOP 之 环绕通知

    在所有的通知类型中，环绕通知最为强大。因为它能完全控制方法的执行过程，所以可以把前一篇文章中所有通知动作都合并到一个单独的通知里。甚至可以控制是否以及何时继续执行原始方法。

    在Spring AOP中，环绕通知必须实现MethodInterceptor接口。这个接口是AOP联盟为了保持不同AOP框架之间的兼容性而定义的。当编写环绕通知时，必须记住——如果要继续执行原始方法，那么就必须调用methodInvocation.proceed()。如果忘记执行这一步，那么原始方法将不会被调用。下面的环绕通知合并了前面所创建的前置、后置和异常通知。

package org.mahz.easyaop.calculator.aop;

import java.util.Arrays;

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;

public class LoggingAroundAdvice implements MethodInterceptor {

	public Object invoke(MethodInvocation invocation) throws Throwable {
		String methodName = invocation.getMethod().getName();

		printTitle(methodName);

		System.out.println("The method " + methodName + "()begin with "
				+ Arrays.toString(invocation.getArguments()));
		try {
			Object returnValue = invocation.proceed();
			System.out.println("The Method " + methodName + "() ends with "
					+ returnValue);
			return returnValue;
		} catch (IllegalArgumentException e) {
			System.out.println(e.getMessage());
			throw e;
		}
	}

	private void printTitle(String methodName) {
		System.out.println("==========================================");
		System.out.println("============ Test " + methodName
				+ " Method =============");
		System.out.println("==========================================");
	}
}

    环绕通知类型非常强大、非常灵活，你甚至可以改变原始的方法参数值以及最终的返回结果。但是因为很容易忘记执行原始的方法，所以在使用这种通知时必须非常小心。

    因为这个通知结合了前面所有通知，所以只需要为代理指定这一个通知即可。

 

<bean id="arithmeticCalculator" class="org.mahz.easyaop.calculator.impl.ArithmeticCalculatorImpl" />
	<bean id="unitCalculator" class="org.mahz.easyaop.calculator.impl.UnitCalculatorImpl" />

	<!-- 
	<bean id="logginBeforeAdvice" class="org.mahz.easyaop.calculator.aop.LoggingBeforeAdvice" />
	<bean id="logginAfterAdvice" class="org.mahz.easyaop.calculator.aop.LoggingAfterAdvice" />
	<bean id="logginThrowsAdvice" class="org.mahz.easyaop.calculator.aop.LoggingThrowsAdvice" />
	 -->
	<bean id="logginAroundAdvice" class="org.mahz.easyaop.calculator.aop.LoggingAroundAdvice" />
	<bean class="org.springframework.aop.framework.autoproxy.BeanNameAutoProxyCreator">
	<property name="beanNames">
		<list>
			<value>*Calculator</value>
		</list>
	</property>
	<property name="interceptorNames">
		<list>
			<!-- 
			<value>logginBeforeAdvice</value>
			<value>logginAfterAdvice</value>
			<value>logginThrowsAdvice</value>
			-->
			<value>logginAroundAdvice</value>
		</list>
	</property>
</bean>

 

    执行结果：

 

==========================================
============ Test add Method =============
==========================================
The method add()begin with [4.0, 0.0]
4.0 + 0.0 = 4.0
The Method add() ends with 4.0
==========================================
============ Test sub Method =============
==========================================
The method sub()begin with [4.0, 0.0]
4.0 - 0.0 = 4.0
The Method sub() ends with 4.0
==========================================
============ Test mul Method =============
==========================================
The method mul()begin with [4.0, 0.0]
4.0 * 0.0 = 0.0
The Method mul() ends with 0.0
==========================================
============ Test div Method =============
==========================================
The method div()begin with [4.0, 0.0]
Division by zero