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

2015-12-24 10:34 453 查看
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:

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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:

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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"

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:

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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:

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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:

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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:

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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"

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:

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<dependency>

<groupId>cglib</groupId>

<artifactId>cglib</artifactId>

<version>2.2.2</version>

</dependency>

运行测试类:

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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:

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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

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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:

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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"

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:

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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:

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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:

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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"

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:

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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:

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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:

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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"

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:

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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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