spring2.0 aop总结

面向切面编程，针对的对象主要是类的方法。也就是说，当某个类（某些类）的某个方法（某些方法）进行一次包装。比如，权限控制，当执行某个方法时，首先判断是否具有某种权限。

这里的包装有两个前提：1，不修改原有类的任何代码；2，用来包装的代码是易插拔的。也就是说，对于某个方法，用于包装它的代码，可以随意地在其执行前/后执行。

 

三个概念：Advice，用于进行包装的类；pointcut，包装操作的切入点；Aspect，切面，一个切面应该包括，Advice和pointcut。

四种类型：Before Advice，After Advice，Around Advice，AfterThrowingAdvice。

 

Spring2.0在AOP控制上实现的非常简化。首先在applicationContext的配置文件中声明两个bean，一个是Advice，另一个是被切入的对象。

 

然后声明一个aspect，一个aspect指定切入的详细信息。

例如，

    <bean id="logBeforeAdvice" class="com.hc.test.LogBeforeAdvice"/>
    <bean id="helloSpeaker" class="com.hc.test.HelloSpeaker"/>

    <aop:config>
        <aop:aspect id="logging" ref="logAdvice">
            <aop:before pointcut="execution(* com.hc.test.IHello.*(..))" method="before"/>
        </aop:aspect>
    </aop:config>

其中<aop:aspect>指定一个切面，ref="logBeforeAdvice"是该切面所使用的类实例。

<aop:before>指定切面处于切入点之前。pointcut="execution(* com.hc.test.IHello.*(..))" method="before"/>指定切入点。method="before"指定该切面所使用的类实例中哪个方法将被执行。

 

HelloSpeaker.java

package com.hc.test;

public class HelloSpeaker implements IHello {
   public void sayHello() throws Exception {
    System.out.println( "Hello baby !");
  }
   public void toHello() {
    System.out.println( "to hello to you");
  }
}

 

IHello.java

package com.hc.test;

public interface IHello {
   public void sayHello() throws Exception;
    
   public void toHello();
}

LogAdvice

package com.hc.test;

import org.aspectj.lang.JoinPoint;

public class LogAdvice {
   public void before(JoinPoint jointPoint) {
    System.out.println( "........the before content of logging.......");
  }
}

在spring 容器中获得一个HelloSpeaker对象，并执行其sayHello()和toHello()方法。

执行结果如下所示。

........the before content of logging.......
Hello baby !
........the before content of logging.......
to hello to you

 

对于AfterAdvice、AroundAdvice和After Throwing Advice示例如下所示。

LogAdvice.java

package com.hc.test;

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.ProceedingJoinPoint;
public class LogAdvice {
   public void before(JoinPoint jointPoint) {
    System.out.println( "........the before content of logging.......");
  }

   public void after(JoinPoint jointPoint) {
    System.out.println( "........the after content of logging.......");
  }

   public Object around(ProceedingJoinPoint jointPoint) {
    System.out.println( "........the begin around content of logging.......");
    Object retVal = null;
     try {
      retVal = jointPoint.proceed();
    } catch(Throwable throwable) {
        
    }
    System.out.println( "........the end around content of logging.......");
     return retVal;
  }

   public void throwing(JoinPoint jointPoint, Throwable throwable) {
    System.out.println( "........the trowing content of logging.......");
  }
}

HelloSpeaker.java

package com.hc.test;

public class HelloSpeaker implements IHello {
   public void test1() {
    System.out.println( "Hello test 1 !");
  }

   public void test2() {
    System.out.println( "Hello test 2 !");
  }

   public void test3() {
    System.out.println( "Hello test 3 !");
  }

   public void test4() throws Exception {
    System.out.println( "Hello test 4 !");
     throw new Exception();
  }
}

Spring配置文件

         < bean id ="logBeforeAdvice" class ="com.hc.test.LogAdvice" />
         < bean id ="helloSpeaker" class ="com.hc.test.HelloSpeaker" />
         < aop:config >
                 < aop:aspect id ="logging" ref ="logBeforeAdvice" >
                         < aop:before pointcut ="execution(* com.hc.test.IHello.test1(..))" method ="before" />
                         < aop:after pointcut ="execution(* com.hc.test.IHello.test2(..))" method ="after" />
                         < aop:around pointcut ="execution(* com.hc.test.IHello.test3(..))" method ="around" />
                         < aop:after-throwing pointcut ="execution(* com.hc.test.IHello.test4(..))" throwing ="throwable" method ="throwing" />
                 </ aop:aspect >
         </ aop:config >