Spring AOP 中 advice 的四种类型 before after throwing advice around

本文主要是介绍Spring AOP 中 advice 的四种类型 before after throwing advice around，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

Spring AOP(Aspect-oriented programming) 是用于切面编程，简单的来说：AOP相当于一个拦截器，去拦截一些处理，例如：当一个方法执行的时候，Spring 能够拦截正在执行的方法，在方法执行的前或者后增加额外的功能和处理。

在Spring AOP中支持4中类型的通知：

1：before advice 在方法执行前执行。

2：after returning advice 在方法执行后返回一个结果后执行。

3：after throwing advice 在方法执行过程中抛出异常的时候执行。

4：Around advice 在方法执行前后和抛出异常时执行，相当于综合了以上三种通知。

下面是一个简单的AOP advice 的例子：

首先给出一个简单的Spring 注入的例子，

定义一个Book类：

package com.myapp.core.aop.advice;public class Book {private  String  name;private  String  url;private   int    pages;public String getName() {return name;}public void setName(String name) {this.name = name;}public String getUrl() {return url;}public void setUrl(String url) {this.url = url;}public int getPages() {return pages;}public void setPages(int pages) {this.pages = pages;}public  void  printName(){System.out.println("Book name "+ this.name);}public  void  printUrl(){System.out.println("Book URL "+this.url);}public  void  printThrowException(){throw  new  IllegalArgumentException();}}

相应的配置文件：

<?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/beanshttp://www.springframework.org/schema/beans/spring-beans-3.0.xsd"><!-- more bean definitions for data access objects go here --><bean id="book" class="com.myapp.core.aop.advice.Book"><property name="name" value="Effective java" /><property name="url" value="www.google.cn"/><property name="pages" value="300" /></bean>
</beans>

对应的测试类：

package com.myapp.core.aop.advice;import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;public class MainTest {public static void main(String[] args) {ApplicationContext  context  = new  ClassPathXmlApplicationContext("resource/aop.xml");Book   book  =   (Book) context.getBean("book");System.out.println("---------------------");book.printName();System.out.println("---------------------");book.printUrl();System.out.println("----------------------");try{book.printThrowException();}catch(Exception e){//  e.printStackTrace();}}
}

输出结果：

三月 20, 2013 11:01:01 上午 org.springframework.context.support.AbstractApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@11e831: startup date [Wed Mar 20 11:01:01 CST 2013]; root of context hierarchy
三月 20, 2013 11:01:01 上午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [resource/aop.xml]
三月 20, 2013 11:01:01 上午 org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons
INFO: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@13b5500: defining beans [book]; root of factory hierarchy
---------------------
Book name Effective java
---------------------
Book URL www.google.cn
----------------------

下面对以上的Book加上Spring AOP advices

1：before advice

before advice将在方法执行前执行，创建一个实现MethodBeforeAdvice接口的类能够定义执行方法前的操作。

类如下：

package com.myapp.core.aop.advice;import java.lang.reflect.Method;import org.springframework.aop.MethodBeforeAdvice;public class BeforeMethod  implements MethodBeforeAdvice {@Overridepublic void before(Method arg0, Object[] arg1, Object arg2)throws Throwable {// TODO Auto-generated method stubSystem.out.println("Before  Method");System.out.println("--------------------");}}

配置对应的bean：

在aop.xml中配置，创建一个BeforeMethod类，一个新的代理命名为：bookProxy

1： target 设置你想拦截的bean

2：interceptorNames设置通知，你想作用于proxy/target上的

对应的配置文件如下：

<?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/beanshttp://www.springframework.org/schema/beans/spring-beans-3.0.xsd"><!-- more bean definitions for data access objects go here --><bean id="book" class="com.myapp.core.aop.advice.Book"><property name="name" value="Effective java" /><property name="url" value="www.google.cn"/><property name="pages" value="300" /></bean><bean id="beforeMethodBean" class="com.myapp.core.aop.advice.BeforeMethod" /><bean id="bookProxy" class="org.springframework.aop.framework.ProxyFactoryBean"><property name="target" ref="book"/><property name="interceptorNames"><list><value>beforeMethodBean</value></list></property></bean>
</beans>

注意：为了使用proxy（代理）我们需要引入 CGLIB2， pom.xml文件中注入如下：

	<dependency><groupId>cglib</groupId><artifactId>cglib</artifactId><version>2.2.2</version></dependency>

运行测试类：

package com.myapp.core.aop.advice;import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;public class MainTest {public static void main(String[] args) {ApplicationContext  context  = new  ClassPathXmlApplicationContext("resource/aop.xml");Book   book  =   (Book) context.getBean("bookProxy");System.out.println("---------------------");book.printName();System.out.println("---------------------");book.printUrl();System.out.println("----------------------");try{book.printThrowException();}catch(Exception e){//  e.printStackTrace();}}
}

注意以上获得的是代理bean；

运行结果如下：

三月 20, 2013 2:18:56 下午 org.springframework.context.support.AbstractApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@eb67e8: startup date [Wed Mar 20 14:18:55 CST 2013]; root of context hierarchy
三月 20, 2013 2:18:56 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [resource/aop.xml]
三月 20, 2013 2:18:57 下午 org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons
INFO: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@157985: defining beans [book,beforeMethodBean,bookProxy]; root of factory hierarchy
---------------------
Before  Method
--------------------
Book name Effective java
---------------------
Before  Method
--------------------
Book URL www.google.cn
----------------------
Before  Method
--------------------

2： after advice

在方法运行返回结果后将执行这个 afterReturning方法，创建的这个类必须实现：AfterReturningAdvice接口

package com.myapp.core.aop.advice;import java.lang.reflect.Method;import org.springframework.aop.AfterReturningAdvice;public class AfterMethod  implements  AfterReturningAdvice {@Overridepublic void afterReturning(Object arg0, Method arg1, Object[] arg2,Object arg3) throws Throwable {// TODO Auto-generated method stubSystem.out.println("-------------------");System.out.println("After  method ");}}

xml配置文件：

<?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/beanshttp://www.springframework.org/schema/beans/spring-beans-3.0.xsd"><!-- more bean definitions for data access objects go here --><bean id="book" class="com.myapp.core.aop.advice.Book"><property name="name" value="Effective java" /><property name="url" value="www.google.cn"/><property name="pages" value="300" /></bean><bean id="beforeMethodBean" class="com.myapp.core.aop.advice.BeforeMethod" /><bean id="afterMethodBean" class="com.myapp.core.aop.advice.AfterMethod" /><bean id="bookProxy" class="org.springframework.aop.framework.ProxyFactoryBean"><property name="target" ref="book"/><property name="interceptorNames"><list><value>beforeMethodBean</value><value>afterMethodBean</value></list></property></bean>
</beans>

运行结果如下：

三月 20, 2013 2:22:19 下午 org.springframework.context.support.AbstractApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@eb67e8: startup date [Wed Mar 20 14:22:19 CST 2013]; root of context hierarchy
三月 20, 2013 2:22:19 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [resource/aop.xml]
三月 20, 2013 2:22:20 下午 org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons
INFO: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@157985: defining beans [book,beforeMethodBean,afterMethodBean,bookProxy]; root of factory hierarchy
---------------------
Before  Method
--------------------
Book name Effective java
-------------------
After  method 
---------------------
Before  Method
--------------------
Book URL www.google.cn
-------------------
After  method 
----------------------
Before  Method
--------------------

3：after throwing advice

当方法执行抛出一个异常后，会执行这个方法，创建一个类实现：ThrowsAdvice接口，创建一个afterThrowing拦截：IllegalArgumentException异常。

类如下：

package com.myapp.core.aop.advice;import org.springframework.aop.ThrowsAdvice;public class ThrowException  implements ThrowsAdvice{public  void  afterThrowing(IllegalArgumentException e)  throws  Throwable{System.out.println("after Throwing  Exception");}
}

xml中配置文件如下：

<?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/beanshttp://www.springframework.org/schema/beans/spring-beans-3.0.xsd"><!-- more bean definitions for data access objects go here --><bean id="book" class="com.myapp.core.aop.advice.Book"><property name="name" value="Effective java" /><property name="url" value="www.google.cn"/><property name="pages" value="300" /></bean><!-- before  advice --><bean id="beforeMethodBean" class="com.myapp.core.aop.advice.BeforeMethod" /><!-- after  advice --><bean id="afterMethodBean" class="com.myapp.core.aop.advice.AfterMethod" /><!-- throwing  advice --><bean id="throwException" class="com.myapp.core.aop.advice.ThrowException" /><bean id="bookProxy" class="org.springframework.aop.framework.ProxyFactoryBean"><property name="target" ref="book"/><property name="interceptorNames"><list><value>beforeMethodBean</value><value>afterMethodBean</value><value>throwException</value></list></property></bean>
</beans>

执行结果如下：

三月 20, 2013 2:37:36 下午 org.springframework.context.support.AbstractApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@eb67e8: startup date [Wed Mar 20 14:37:36 CST 2013]; root of context hierarchy
三月 20, 2013 2:37:36 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [resource/aop.xml]
三月 20, 2013 2:37:36 下午 org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons
INFO: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@157985: defining beans [book,beforeMethodBean,afterMethodBean,throwException,bookProxy]; root of factory hierarchy
---------------------
Before  Method
--------------------
Book name Effective java
-------------------
After  method 
---------------------
Before  Method
--------------------
Book URL www.google.cn
-------------------
After  method 
----------------------
Before  Method
--------------------
after Throwing  Exception

4：Around advice

这个advice 联合了上面的三个advices，在方法执行期间执行，创建一个类实现MethodInterceptor接口，需要在方法中执行Object result = methodInvocation.proceed();方法才能得到执行，否则方法不会执行。

类如下：

package com.myapp.core.aop.advice;import java.util.Arrays;import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;public class AroundMethod  implements MethodInterceptor{@Overridepublic Object invoke(MethodInvocation methodInvocation) throws Throwable {// TODO Auto-generated method stubSystem.out.println("method  name:" + methodInvocation.getMethod().getName());System.out.println("method  arguments" + Arrays.toString(methodInvocation.getArguments()));System.out.println("Around  method : before ");try{Object result = methodInvocation.proceed();System.out.println("Around method : after ");return  result;}catch(IllegalArgumentException e){System.out.println("Around method : throw  an  exception ");throw  e;}}}

配置文件如下：

<?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/beanshttp://www.springframework.org/schema/beans/spring-beans-3.0.xsd"><!-- more bean definitions for data access objects go here --><bean id="book" class="com.myapp.core.aop.advice.Book"><property name="name" value="Effective java" /><property name="url" value="www.google.cn"/><property name="pages" value="300" /></bean><bean id="aroundMethod"  class="com.myapp.core.aop.advice.AroundMethod" /><bean id="bookProxy" class="org.springframework.aop.framework.ProxyFactoryBean" ><property name="target" ref="book"/><property name="interceptorNames"><list><value>aroundMethod</value></list></property></bean>
</beans>

测试结果：

三月 20, 2013 3:02:19 下午 org.springframework.context.support.AbstractApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@eb67e8: startup date [Wed Mar 20 15:02:19 CST 2013]; root of context hierarchy
三月 20, 2013 3:02:19 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [resource/aop.xml]
三月 20, 2013 3:02:19 下午 org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons
INFO: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@e29127: defining beans [book,aroundMethod,bookProxy]; root of factory hierarchy
---------------------
method  name:printName
method  arguments[]
Around  method : before 
Book name Effective java
Around method : after 
---------------------
method  name:printUrl
method  arguments[]
Around  method : before 
Book URL www.google.cn
Around method : after 
----------------------
method  name:printThrowException
method  arguments[]
Around  method : before 
Around method : throw  an  exception

around advice得到实现。 over

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