AOP简介及Spring AOP的4种实现

AOP

AOP（Aspect Oriented Programing，面向切面编程）用于在不侵入原有代码的基础上，为代码统一添加新功能，例如性能监控、日志记录、事务管理等。AOP的原理如图所示：

其中：
1）连接点（Jointpoint），表示方法执行的某个位置，如方法调用前、方法调用后、方法抛出异常等；
2）通知（Advice），表示需要在某个连接点加入的新功能，通知包括以下5种类型：Before advice，After returning advice，After throwing advice，After (finally) advice，Around advice；
3）切入点（Pointcut），用于描述某些类的某些方法；
4）切面（Aspect），通知和切入点组成切面，通过切面实现在指定类的指定方法上，加入通知。

Spring AOP的4种实现

Spring AOP的实现基于动态代理，有以下4种实现方式：
1）基于Aspect注解；
2）基于aop标签配置；
3）基于ProxyFactoryBean；
4）基于DefaultAdvisorAutoProxyCreator。
通过一个例子分别说明上述4种实现方式。例子中包含TestService接口及其实现TestServiceImpl，TestServiceImpl的test方法输出“execute test method”：

package com.magicwt.service;

public interface TestService {

    public void test();

}

package com.magicwt.service;

public interface TestService {

public void test();

}

package com.magicwt.service.impl;

import com.magicwt.service.TestService;

public class TestServiceImpl implements TestService {

    public void test() {
        System.out.println("execute test method");
    }

}

package com.magicwt.service.impl;

import com.magicwt.service.TestService;

public class TestServiceImpl implements TestService {

public void test() {

System.out.println("execute test method");

}

main方法初始化Spring上下文，获取TestService实例，并执行test方法：

package com.magicwt;

import com.magicwt.service.TestService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test {

    public static void main(String[] args) {
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("context.xml");
        TestService testService = (TestService) applicationContext.getBean("testService");
        testService.test();
    }
}

package com.magicwt;

import com.magicwt.service.TestService;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test {

public static void main(String[] args) {

ApplicationContext applicationContext = new ClassPathXmlApplicationContext("context.xml");

TestService testService = (TestService) applicationContext.getBean("testService");

testService.test();

}

Spring上下文配置文件context.xml：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       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-3.2.xsd">

    <bean id="testService" class="com.magicwt.service.impl.TestServiceImpl"/>

</beans>

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

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-3.2.xsd">

</beans>

执行main方法，输出：

execute test method

以下通过Spring AOP，在test方法调用前和调用后，增加切面。

基于Aspect注解

新建类TestAspect：

package com.magicwt.aop;

import org.aspectj.lang.annotation.*;
import org.springframework.stereotype.Component;

/**
 * 配置切面和组件
 */
@Component
@Aspect
public class TestAspect {

    /**
     * 配置切入点，com.magicwt.service包下所有类的所有方法
     */
    @Pointcut("execution(* com.magicwt.service..*(..))")
    public void pointcut() {}

    /**
     * 方法调用前通知
     */
    @Before("pointcut()")
    public void before() {
        System.out.println("execute before advice");
    }

    /**
     * 方法调用后通知
     */
    @After("pointcut()")
    public void after() {
        System.out.println("execute after advice");
    }

}

package com.magicwt.aop;

import org.aspectj.lang.annotation.*;

import org.springframework.stereotype.Component;

/**

* 配置切面和组件

@Component

@Aspect

public class TestAspect {

/**

* 配置切入点，com.magicwt.service包下所有类的所有方法

@Pointcut("execution(* com.magicwt.service..*(..))")

public void pointcut() {}

/**

* 方法调用前通知

@Before("pointcut()")

public void before() {

System.out.println("execute before advice");

}

/**

* 方法调用后通知

@After("pointcut()")

public void after() {

System.out.println("execute after advice");

}

context.xml修改为：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:aop="http://www.springframework.org/schema/aop"
       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-3.2.xsd
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context-3.2.xsd
    http://www.springframework.org/schema/aop
    http://www.springframework.org/schema/aop/spring-aop-3.2.xsd">

    <bean id="testService" class="com.magicwt.service.impl.TestServiceImpl"/>

    <!-- 扫描com.magicwt.aop包下的组件，进行初始化 -->
    <context:component-scan base-package="com.magicwt.aop"/>

    <!-- 根据注解自动创建代理，织入切面 -->
    <aop:aspectj-autoproxy />

</beans>

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

xmlns:context="http://www.springframework.org/schema/context"

xmlns:aop="http://www.springframework.org/schema/aop"

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-3.2.xsd

http://www.springframework.org/schema/context

http://www.springframework.org/schema/context/spring-context-3.2.xsd

http://www.springframework.org/schema/aop

http://www.springframework.org/schema/aop/spring-aop-3.2.xsd">

<context:component-scan base-package="com.magicwt.aop"/>

<aop:aspectj-autoproxy />

</beans>

执行main方法，输出：

execute before advice
execute test method
execute after advice

基于aop标签配置

TestAspect：

package com.magicwt.aop;

public class TestAspect {

    public void before() {
        System.out.println("execute before advice");
    }

    public void after() {
        System.out.println("execute after advice");
    }

}

package com.magicwt.aop;

public class TestAspect {

public void before() {

System.out.println("execute before advice");

}

public void after() {

System.out.println("execute after advice");

}

context.xml修改为：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:aop="http://www.springframework.org/schema/aop"
       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-3.2.xsd
    http://www.springframework.org/schema/aop
    http://www.springframework.org/schema/aop/spring-aop-3.2.xsd">

    <bean id="testService" class="com.magicwt.service.impl.TestServiceImpl"/>

    <bean id="testAspect" class="com.magicwt.aop.TestAspect"/>

    <aop:config>
        <!-- 配置切面 -->
        <aop:aspect ref="testAspect">
            <!-- 配置切入点，com.magicwt.service包下所有类的所有方法 -->
            <aop:pointcut id="pointcut" expression="execution(* com.magicwt.service..*(..))"/>
            <!-- 配置方法调用前通知 -->
            <aop:before method="before" pointcut-ref="pointcut"/>
            <!-- 配置方法调用后通知 -->
            <aop:after method="after" pointcut-ref="pointcut"/>
        </aop:aspect>
    </aop:config>

</beans>

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

xmlns:aop="http://www.springframework.org/schema/aop"

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-3.2.xsd

http://www.springframework.org/schema/aop

http://www.springframework.org/schema/aop/spring-aop-3.2.xsd">

<aop:config>

<aop:aspect ref="testAspect">

<aop:pointcut id="pointcut" expression="execution(* com.magicwt.service..*(..))"/>

<aop:before method="before" pointcut-ref="pointcut"/>

<aop:after method="after" pointcut-ref="pointcut"/>

</aop:aspect>

</aop:config>

</beans>

执行main方法，输出：

execute before advice
execute test method
execute after advice

基于ProxyFactoryBean

新建类TestAdvice，实现接口MethodBeforeAdvice、AfterReturningAdvice，重写before、afterReturning方法：

package com.magicwt.aop;

import org.springframework.aop.AfterReturningAdvice;
import org.springframework.aop.MethodBeforeAdvice;

import java.lang.reflect.Method;

public class TestAdvice implements MethodBeforeAdvice, AfterReturningAdvice {

    @Override
    public void before(Method method, Object[] args, Object target) throws Throwable {
        System.out.println("execute before advice");
    }

    @Override
    public void afterReturning(Object returnValue, Method method, Object[] args, Object target) throws Throwable {
        System.out.println("execute after advice");
    }
}

package com.magicwt.aop;

import org.springframework.aop.AfterReturningAdvice;

import org.springframework.aop.MethodBeforeAdvice;

import java.lang.reflect.Method;

public class TestAdvice implements MethodBeforeAdvice, AfterReturningAdvice {

@Override

public void before(Method method, Object[] args, Object target) throws Throwable {

System.out.println("execute before advice");

}

@Override

public void afterReturning(Object returnValue, Method method, Object[] args, Object target) throws Throwable {

System.out.println("execute after advice");

}

context.xml修改为：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       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-3.2.xsd">

    <bean id="realTestService" class="com.magicwt.service.impl.TestServiceImpl"/>

    <bean id="testAdvice" class="com.magicwt.aop.TestAdvice"/>

    <!-- 配置切入点，com.magicwt.service包下所有类的所有方法 -->
    <bean id="pointcut" class="org.springframework.aop.aspectj.AspectJExpressionPointcut">
        <property name="expression" value="execution(* com.magicwt.service..*(..))"/>
    </bean>

    <!-- 配置切面 -->
    <bean id="advisor" class="org.springframework.aop.support.DefaultPointcutAdvisor">
        <property name="advice" ref="testAdvice"/>
        <property name="pointcut" ref="pointcut"/>
    </bean>

    <!-- 创建代理，织入切面 -->
    <bean id="testService" class="org.springframework.aop.framework.ProxyFactoryBean">
        <property name="target" ref="realTestService"/>
        <property name="interceptorNames" value="advisor" />
        <property name="proxyInterfaces" value="com.magicwt.service.TestService" />
    </bean>

</beans>

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

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-3.2.xsd">

</bean>

</bean>

</bean>

</beans>

执行main方法，输出：

execute before advice
execute test method
execute after advice

基于DefaultAdvisorAutoProxyCreator

与基于ProxyFactoryBean的实现相比，只需修改context.xml：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       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-3.2.xsd">

    <bean id="testService" class="com.magicwt.service.impl.TestServiceImpl"/>

    <bean id="testAdvice" class="com.magicwt.aop.TestAdvice"/>

    <!-- 配置切入点，com.magicwt.service包下所有类的所有方法 -->
    <bean id="pointcut" class="org.springframework.aop.aspectj.AspectJExpressionPointcut">
        <property name="expression" value="execution(* com.magicwt.service..*(..))"/>
    </bean>

    <!-- 配置切面 -->
    <bean id="advisor" class="org.springframework.aop.support.DefaultPointcutAdvisor">
        <property name="advice" ref="testAdvice"/>
        <property name="pointcut" ref="pointcut"/>
    </bean>

    <!-- 通过DefaultAdvisorAutoProxyCreator自动创建代理，织入切面 -->
    <bean class="org.springframework.aop.framework.autoproxy.DefaultAdvisorAutoProxyCreator"/>

</beans>

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

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-3.2.xsd">

</bean>

</bean>

</beans>

执行main方法，输出：

execute before advice
execute test method
execute after advice

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原文地址: http://magicwt.com/2013/09/15/aop%e7%ae%80%e4%bb%8b%e5%8f%8aspring-aop%e7%9a%844%e7%a7%8d%e5%ae%9e%e7%8e%b0/

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