应用Spring的注解方式实现AOP

一、使用实例

1、导入需要的包

首先，为了使用Spring的AOP注解功能，必须在pom.xml中导入如下几个包。

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<properties>

<org.springframework-version>3.2.9.RELEASE</org.springframework-version>

<commons-logging.version>1.1</commons-logging.version>

<org.slf4j-version>1.7.2</org.slf4j-version>

</properties>

<dependencies>

<!-- Spring -->

<dependency>

<groupId>org.springframework</groupId>

<artifactId>spring-context</artifactId>

<version>${org.springframework-version}</version>

<exclusions>

<!-- Exclude Commons Logging in favor of SLF4j -->

<exclusion>

<groupId>commons-logging</groupId>

<artifactId>commons-logging</artifactId>

</exclusion>

</exclusions>

</dependency>

<dependency>

<groupId>org.springframework</groupId>

<artifactId>spring-webmvc</artifactId>

<version>${org.springframework-version}</version>

</dependency>

<dependency>

<groupId>org.springframework</groupId>

<artifactId>spring-test</artifactId>

<version>${org.springframework-version}</version>

<scope>test</scope>

</dependency>

<dependency>

<groupId>org.springframework</groupId>

<artifactId>spring-context-support</artifactId>

<version>${org.springframework-version}</version>

</dependency>

<dependency>

<groupId>org.springframework</groupId>

<artifactId>spring-aop</artifactId>

<version>${org.springframework-version}</version>

</dependency>

<dependency>

<groupId>org.springframework</groupId>

<artifactId>spring-orm</artifactId>

<version>${org.springframework-version}</version>

</dependency>

<dependency>

<groupId>org.springframework</groupId>

<artifactId>spring-web</artifactId>

<version>${org.springframework-version}</version>

</dependency>

<dependency>

<groupId>org.dbunit</groupId>

<artifactId>dbunit</artifactId>

<version>2.4.6</version>

<scope>test</scope>

</dependency>

<dependency>

<groupId>org.springframework</groupId>

<artifactId>spring-jdbc</artifactId>

<version>${org.springframework-version}</version>

<exclusions>

<!-- Exclude Commons Logging in favor of SLF4j -->

<exclusion>

<groupId>commons-logging</groupId>

<artifactId>commons-logging</artifactId>

</exclusion>

</exclusions>

</dependency>

<dependency>

<groupId>commons-logging</groupId>

<artifactId>commons-logging</artifactId>

<version>${commons-logging.version}</version>

</dependency>

<!-- Logging -->

<dependency>

<groupId>org.slf4j</groupId>

<artifactId>slf4j-api</artifactId>

<version>${org.slf4j-version}</version>

</dependency>

<dependency>

<groupId>log4j</groupId>

<artifactId>log4j</artifactId>

<version>1.2.15</version>

<exclusions>

<exclusion>

<groupId>javax.mail</groupId>

<artifactId>mail</artifactId>

</exclusion>

<exclusion>

<groupId>javax.</groupId>

<artifactId>jms</artifactId>

</exclusion>

<exclusion>

<groupId>com.sun.jdmk</groupId>

<artifactId>jmxtools</artifactId>

</exclusion>

<exclusion>

<groupId>com.sun.jmx</groupId>

<artifactId>jmxri</artifactId>

</exclusion>

</exclusions>

<scope>runtime</scope>

</dependency>

<dependency>

<groupId>org.aspectj</groupId>

<artifactId>aspectjrt</artifactId>

<version>1.6.11</version>

</dependency>

<dependency>

<groupId>org.aspectj</groupId>

<artifactId>aspectjweaver</artifactId>

<version>1.6.11</version>

</dependency>

<dependency>

<groupId>cglib</groupId>

<artifactId>cglib</artifactId>

<version>2.1</version>

</dependency>

</dependencies>

2、配置文件applicationContext.xml

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

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

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

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

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

xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
<span style="color:#FF0000;">http://www.springframework.org/schema/aop

&n
a41b
bsp; http://www.springframework.org/schema/aop/spring-aop-2.5.xsd</span> http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<!-- 声明注解方式加载bean-->

<context:annotation-config/>

<!-- 要加载的bean的包路径-->

<context:component-scan base-package="com.meituan.hyt.test.service"/>

<!-- 自动扫描被@Aspect注解的bean-->

<aop:aspectj-autoproxy/>

<bean id="myInterceptor" class="com.meituan.hyt.test.aop.MyInterceptor"/>

</beans>

3、编写自己的业务接口和实现类，注解为spring bean

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package com.meituan.hyt.test.service;

public interface PersonService {

public void save(String name);

public void update(int name);

public void throwException();

public String getPersonName();

}

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package com.meituan.hyt.test.service;

import org.springframework.stereotype.Service;

@Service(value = "personService")

public class PersonServiceImpl implements PersonService {

@Override

public String getPersonName() {

System.out.println("我是getPersonName()方法。。。");

return "返回结果";

}

@Override

public void save(String name) {

System.out.println("我是save()方法。。。");

}

@Override

public void update(int name) {

System.out.println("我是update()方法。。。");

}

@Override

public void throwException() {

System.out.println("我是throwException()方法。。。");

throw new RuntimeException("异常了。。");

}

}

4、编写切面

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package com.meituan.hyt.test.aop;

import org.aspectj.lang.ProceedingJoinPoint;

import org.aspectj.lang.annotation.*;

/**

* Created by heyutao on 15/11/2.

*/

@Aspect

public class MyInterceptor {

@Pointcut("execution(* com.meituan.hyt.test.service.*.*(..))")

//声明一个切入点

private void anyMethod() {

}

@Before("anyMethod() && args(name)")//声明前置通知

public void doBefore(String name) {

System.out.println("前置通知");

System.out.println("---" + name + "---");

}

@AfterReturning(pointcut = "anyMethod()", returning = "result")//声明后置通知

public void doAfterReturning(String result) {

System.out.println("后置通知");

System.out.println("---" + result + "---");

}

@AfterThrowing(pointcut = "anyMethod()", throwing = "e")//声明例外通知

public void doAfterThrowing(Exception e) {

System.out.println("例外通知");

System.out.println(e.getMessage());

}

@After("anyMethod()")//声明最终通知

public void doAfter() {

System.out.println("最终通知");

}

@Around("anyMethod()")//声明环绕通知

public Object doAround(ProceedingJoinPoint pjp) throws Throwable {

System.out.println("进入方法---环绕通知");

//显示调用，确保被代理的方法被调用

Object o = pjp.proceed();

System.out.println("退出方法---环绕通知");

return o;

}

}

1、@Pointcut("execution(* com.meituan.hyt.test.service.*.*(..))")声明一个切入点，可以拦截具体到某个方法，即在执行此方法之前、之后、最终、异常……时可以执行的其他业务方法（通知advice）；

括号内的意思是：拦截某个方法，返回值是所有类型（第一个*），要拦截的是com.aoptest.service包及其子包下的所有类（..*）类下所有的方法（第三个.*）

2、args(name)

可以得到参数值，此时args(name)限制条件限定了"eexecution(* com.meituan.hyt.test.service.*.*(..))"中只拦截参数个数只有1个且类型为String的方法，而不是所有方法

5、编写测试方法

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import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.meituan.hyt.test.service.PersonService;

/**

* Created by heyutao on 15/11/2.

*/

public class Main {

public static void main(String[] args) {

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

PersonService personService = (PersonService) cxt.getBean("personService");

System.out.println("----------------save start------------");

personService.save("我是参数");

System.out.println("----------------save end------------");

System.out.println("----------------update start------------");

personService.update(100);

System.out.println("----------------update end------------");

System.out.println("----------------throwException start------------");

personService.throwException();

System.out.println("----------------throwException end------------");

System.out.println("----------------getPersonName start------------");

String result = personService.getPersonName();

System.out.println(result);

System.out.println("----------------getPersonName end------------");

}

}

6、执行结果

----------------save start------------

进入方法---环绕通知

前置通知

---我是参数---

我是save()方法。。。

退出方法---环绕通知

最终通知

后置通知

---null---

----------------save end------------

----------------update start------------

进入方法---环绕通知

我是update()方法。。。

退出方法---环绕通知

最终通知

后置通知

---null---

----------------update end------------

----------------throwException start------------

进入方法---环绕通知

我是throwException()方法。。。

最终通知

例外通知

异常了。。

Exception in thread "main" java.lang.RuntimeException: 异常了。。

at com.meituan.hyt.test.service.PersonServiceImpl.throwException(PersonServiceImpl.java:32)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

at java.lang.reflect.Method.invoke(Method.java:597)

at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)

at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183)

at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)

at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:80)

at com.meituan.hyt.test.aop.MyInterceptor.doAround(MyInterceptor.java:51)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

at java.lang.reflect.Method.invoke(Method.java:597)

at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethodWithGivenArgs(AbstractAspectJAdvice.java:621)

at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethod(AbstractAspectJAdvice.java:610)

at org.springframework.aop.aspectj.AspectJAroundAdvice.invoke(AspectJAroundAdvice.java:65)

at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)

at org.springframework.aop.aspectj.AspectJAfterAdvice.invoke(AspectJAfterAdvice.java:42)

at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)

at org.springframework.aop.framework.adapter.AfterReturningAdviceInterceptor.invoke(AfterReturningAdviceInterceptor.java:51)

at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)

at org.springframework.aop.aspectj.AspectJAfterThrowingAdvice.invoke(AspectJAfterThrowingAdvice.java:55)

at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)

at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:91)

at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)

at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)

at com.sun.proxy.$Proxy12.throwException(Unknown Source)

at Main.main(Main.java:24)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

at java.lang.reflect.Method.invoke(Method.java:597)

at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)

二、原理分析

1、命名空间

<aop:aspectj-autoproxy proxy-target-class="true"> 该命名空间会交给org.springframework.aop.config.AopNamespaceHandler处理，并在AspectJAutoProxyBeanDefinitionParser中，会执行parse方法解析配置：

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public BeanDefinition parse(Element element, ParserContext parserContext) {

AopNamespaceUtils.registerAspectJAnnotationAutoProxyCreatorIfNecessary(parserContext, element);

extendBeanDefinition(element, parserContext);

return null;

}

其中AopNamespaceUtils.registerAspectJAnnotationAutoProxyCreatorIfNecessary(parserContext, element);目的是注册AnnotationAwareAspectJAutoProxyCreator：

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if (registry.containsBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME)) {

BeanDefinition apcDefinition = registry.getBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME);

if (!cls.getName().equals(apcDefinition.getBeanClassName())) {

int currentPriority = findPriorityForClass(apcDefinition.getBeanClassName());

int requiredPriority = findPriorityForClass(cls);

if (currentPriority < requiredPriority) {

apcDefinition.setBeanClassName(cls.getName());

}

}

return null;

}

即首先判断当前容器中是否包含名字为AUTO_PROXY_CREATOR_BEAN_NAME的Bean， 如果包含：然后判断优先级，谁优先级高谁获胜，即最后那个获胜的是实际的AutoProxyCreator。到此我们可以看到跟使用xml配置的方式 "<bean class="org.springframework.aop.aspectj.autoproxy.AspectJAwareAdvisorAutoProxyCreator">"配置没什么区别，除了没有名字外。

2、AspectJAwareAdvisorAutoProxyCreator

AspectJAwareAdvisorAutoProxyCreator的注册，对于AOP的实现基本就靠这个类实现。AspectJAwareAdvisorAutoProxyCreator实现了SmartInstantiationAwareBeanPostProcessor这个接口，它是BeanPostProcessor的子接口。

BeanPostProcessor接口作用是：如果这个接口的某个实现类被注册到某个容器，那么spring容器的每个受管Bean在调用初始化方法之前，都会获得该接口实现类的一个回调，回调方法包括postProcessBeforeInstantiation以及postProcessAfterInstantiation方法。AspectJAwareAdvisorAutoProxyCreator的实现原理就是在回调方法中，找到所有的标有@AspectJ类中的增加方法，即标有@Before,@After,@AfterReturning,@Around等注解的方法，并且从中挑出能cut到当前bean的advisor，一个增强方法对应Advisor，最终形成一个Advisor的列表，并且是有序的集合，顺序分别是Around,
Before, After, AfterReturning, AfterThrowing。然后将这个Advisor的列表作为参数，生成目标对象的代理对象，并返回。动态生成代理对象的方式有两种：jdk动态代理和cglib。