Spring-AOP 通过配置文件实现环绕增强

小小工匠

发布于 2021-08-16 16:39:44

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发布于 2021-08-16 16:39:44

文章被收录于专栏：小工匠聊架构

文章目录

概述

环绕增强允许在目标类方法调用前后织入横切逻辑，它综合实现了前置，后置增强两者的功能.

实例

代码已托管到Github—> https://github.com/yangshangwei/SpringMaster

下面是我们用环绕增强同时实现上面的我们的示例。步骤如下：创建业务接口类：Waiter.java 创建业务实现类：NativeWaiter.java 创建业务增强类：GreetingInterceptor.java 创建配置文件：conf-advice.xml 创建增强测试类：MethodInterceptorTest.java

业务接口类

package com.xgj.aop.spring.advice.methodInterceptor;

public interface Waiter {

	void greetTo(String name);

	void serverTo(String name);
}

业务实现类

package com.xgj.aop.spring.advice.methodInterceptor;

public class NaiveWaiter implements Waiter {

	@Override
	public void greetTo(String name) {
		System.out.println("greetTo " + name);
	}

	@Override
	public void serverTo(String name) {
		System.out.println("serverTo " + name);
	}

}

业务增强类GreetingInterceptor.java

package com.xgj.aop.spring.advice.methodInterceptor;

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

public class GreetingInterceptor implements MethodInterceptor {
	/**
	 * 截取目标类方法的执行，并在前后添加横切逻辑
	 * 
	 * @param invocation
	 *            封装了目标方法和入参数组以及目标方法所带的实例对象
	 * @return 代理对象
	 * @throws Throwable
	 */
	@Override
	public Object invoke(MethodInvocation invocation) throws Throwable {
		// 获取目标方法的入参
		Object[] args = invocation.getArguments();
		// 在目标方法执行前调用
		String clientName = (String) args[0];
		System.out.println("GreetingInterceptor：How are you!" + clientName);
		// 利用反射机制来调用目标方法
		Object object = invocation.proceed();
		// 在目标方法执行后调用
		System.out.println("GreetingInterceptor: please enjoy youself!");
		return object;
	}

}

Spring直接使用AOP联盟所定义的MethodInterceptor作为环绕增强的接口，该接口拥有唯一的接口方法

public Object invoke(MethodInvocation invocation) throws Throwable

MethodInvocation不但封装了目标方法及其入参数组，还封装了目标方法所在的实例对象。通过MethodInvocation的getArguments（）方法可以获取到目标方法的入参数组，通过proceed（）方法反射调用目标实例相应的方法。

通过在实现类中定义横切逻辑可以很容易的实现方法前后的增强。

接下来在配置文件中对其进行配置：

<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:p="http://www.springframework.org/schema/p"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
	
	<bean id="target" class="com.xgj.aop.spring.advice.methodInterceptor.NaiveWaiter"/>
	
	<bean id="greetingAroundAdvice" class="com.xgj.aop.spring.advice.methodInterceptor.GreetingInterceptor">bean>
	
	<bean id="waiter" class="org.springframework.aop.framework.ProxyFactoryBean"
		p:proxyInterfaces="com.xgj.aop.spring.advice.methodInterceptor.Waiter"
		p:interceptorNames="greetingAroundAdvice"
		p:target-ref="target"/>

beans>

编写单元测试

package com.xgj.aop.spring.advice.methodInterceptor;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MethodInterceptorTest {

	@Test
	public void test() {
		ApplicationContext ctx = new ClassPathXmlApplicationContext(
				"classpath:com/xgj/aop/spring/advice/methodInterceptor/conf-advice.xml");

		Waiter waiter = ctx.getBean("waiter", Waiter.class);
		waiter.greetTo("Xiao");
		waiter.serverTo("GongJiang");
	}

}

运行结果