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