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

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/beans
           http://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 {

    @Override
    public void before(Method arg0, Object[] arg1, Object arg2)
            throws Throwable {
        // TODO Auto-generated method stub

        System.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/beans
           http://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 {

    @Override
    public void afterReturning(Object arg0, Method arg1, Object[] arg2,
            Object arg3) throws Throwable {
        // TODO Auto-generated method stub

        System.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/beans
           http://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/beans
           http://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{

    @Override
    public Object invoke(MethodInvocation methodInvocation) throws Throwable {
        // TODO Auto-generated method stub

        System.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/beans
           http://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