应用Spring的注解方式实现AOP

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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。

<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

<?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       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

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();}

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

package com.meituan.hyt.test.aop;import org.aspectj.lang.ProceedingJoinPoint;import org.aspectj.lang.annotation.*;/** * Created by heyutao on 15/11/2. */@Aspectpublic 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

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：

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：

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。具体请参考http://blog.csdn.net/heyutao007/article/details/49738887

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