Spring 自动代理创建器详细介绍及简单实例

Spring 自动代理创建器

前言:

在经典的spring Aop中,可以手工为目标Bean创建代理Bean,配置文件必须为每一个需要增强的Bean声明一个代理,结果配置文件里声明了大量的代理Bean。

在经典的Spring Aop中,Spring提供了自动代理创建器(Aotu proxy creator),有了自动代理创建器,就不再需要使用ProxyFactoryBean手工地创建代理了。

接口Animal和Book:


 package com.zzj.aop; public interface Animal { public void eat(); public void drink(); }
package com.zzj.aop; 
 
public interface Book { 
 public void read(); 
} 

目标类:

package com.zzj.aop; 
 
public class Human implements Animal, Book{ 
 @Override 
 public void eat() { 
  System.out.println("eat..."); 
 } 
 
 @Override 
 public void drink() { 
  System.out.println("drink..."); 
 } 
 
 @Override 
 public void read() { 
  System.out.println("read..."); 
 } 
} 

前置通知和后置通知:

package com.zzj.aop; 
 
import java.lang.reflect.Method; 
 
import org.springframework.aop.MethodBeforeAdvice; 
 
public class MethodBefore implements MethodBeforeAdvice { 
 
 public void before(Method arg0, Object[] arg1, Object arg2) 
   throws Throwable { 
  System.out.println("before " + arg0.getName()); 
 } 
 
} 

package com.zzj.aop; 
 
import java.lang.reflect.Method; 
 
import org.springframework.aop.AfterReturningAdvice; 
 
public class MethodAfter implements AfterReturningAdvice { 
 
 public void afterReturning(Object arg0, Method arg1, Object[] arg2, 
   Object arg3) throws Throwable { 
  System.out.println( "after " + arg1.getName()); 
 } 
 
} 

Spring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.xsd"> 
  <!-- 定义目标对象 --> 
  <bean id="human" class="com.zzj.aop.Human"></bean> 
  
  <!-- 定义通知 --> 
  <bean id="beforeAdvice" class="com.zzj.aop.MethodBefore"></bean> 
  <bean id="afterAdvice" class="com.zzj.aop.MethodAfter"></bean> 
  
  <!-- 定义切入点 --> 
  <bean id="methodNamePointcut" 
   class="org.springframework.aop.support.NameMatchMethodPointcut"> 
   <property name="mappedNames"> 
    <list> 
     <value>eat</value> 
     <value>read</value> 
    </list> 
   </property> 
  </bean> 
  
  <!-- 定义后置增强器(关联通知和切入点) --> 
  <bean id="AfterMethodNameAdvisor" 
   class="org.springframework.aop.support.DefaultPointcutAdvisor"> 
   <property name="advice" ref="afterAdvice"></property> 
   <property name="pointcut" ref="methodNamePointcut"></property> 
  </bean> 
  <!-- 定义前置增强器(关联通知和切入点) --> 
  <bean id="BeforeMethodNameAdvisor" 
   class="org.springframework.aop.aspectj.AspectJExpressionPointcutAdvisor"> 
   <property name="advice" ref="beforeAdvice"></property> 
   <property name="expression"> 
    <value>execution(* *.*in*(..))</value><!-- 可匹配drink --> 
   </property> 
  </bean> 
  
  <!-- 定义自动代理创建器 --> 
  <bean class="org.springframework.aop.framework.autoproxy.BeanNameAutoProxyCreator"> 
   <property name="beanNames"> 
    <list> 
     <value>*human</value> 
    </list> 
   </property> 
   <property name="interceptorNames"> 
    <list> 
     <value>AfterMethodNameAdvisor</value> 
     <value>BeforeMethodNameAdvisor</value> 
    </list> 
   </property> 
  </bean> 
</beans> 

以上自动代理器可以为以human结尾的Bean创建代理。

测试:


package com.zzj.aop; 
 
import org.springframework.context.ApplicationContext; 
import org.springframework.context.support.ClassPathXmlApplicationContext; 
 
public class Test { 
 
 /** 
  * @param args 
  */ 
 public static void main(String[] args) { 
  ApplicationContext context = new ClassPathXmlApplicationContext( 
    "applicationContext.xml"); 
  Animal animal = (Animal) context.getBean("human"); 
  Book book = (Book) animal; 
  animal.eat(); 
  animal.drink(); 
  book.read(); 
 
 } 
 
} 

输出:

eat... 
after eat 
before drink 
drink... 
read... 
after read 

Spring还提供了另一个自动代理创建器:DefaultAdvisorAutoProxyCreator。这个自动代理创建器不需要任何配置,他会自动检查Ioc容器里声明的每一个增强器和Bean。如果存在与增强器切入点匹配的的Bean,那么DefaultAdvisorAutoProxyCreator将自动为其创建代理。

<bean class="org.springframework.aop.framework.autoproxy.DefaultAdvisorAutoProxyCreator"/> 

需要注意的是,DefaultAdvisorAutoProxyCreator可能会代理那些不希望被代理的目标Bean,所以使用时要格外小心。

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