Spring AOP Step-by-step(1)

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一: 概念

Aspect,常译为“方面”,是对施加于不同Class实例的相同问题域的抽象。

二: 参与者

(1) Pointcut: ”方面”的切点--用来决定是否执行Advice的谓词

(2) Advice: 对”方面”的处理

(3) Advisor: Pointcut和Advice的粘合剂

三：Step-by-step

1 Bean: IShape, Rectange, Circle(代码忽略)

   IShape.java:IShape接口

package com.rainsoft.exercise1.aop;

/**
 * Interface for shapes like "circle", "rectange" etc.
 * @author RainS.Yang
 * @version 1.0
 */
public interface IShape {
    void draw();
}

Rectange.java:IShape的一个实现

package com.rainsoft.exercise1.aop;

/**
 * @author RainS.Yang
 * @version 1.0
 */
public class Rectange implements IShape {
    public void draw() {
        System.out.println("Rectange is drawn.");
    }
}

Note:

(1) SpringAOP Framework缺省通过Dynamic Proxy实现,所以要定义接口;而且接口编程被强烈建议

2 Advice:以MethodBeforeAdvice为例

    TimestampMethodBeforeAdvice.java

package com.rainsoft.exercise1.aop;

import java.lang.reflect.Method;
import java.text.SimpleDateFormat;
import java.util.Date;

import org.springframework.aop.MethodBeforeAdvice;

/**
 * Print timestamp to stdout when enter specified methods(pointcuts)
 *
 * @author RainS.Yang
 * @version 1.0
 */
public class TimestampMethodBeforeAdvice implements MethodBeforeAdvice {
    SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH/mm/ss");

    public void before(Method method, Object[] args, Object target)
            throws Throwable {
        System.out.println(df.format(new Date()) + ":entering method - "
                + method.getName());
    }
}

Note:

(1) Spring AOP Frame内置5种Advice,所有Advice都从org.aopalliance.aop.Advice继承来

 

  Spring AOP Frmaework支持的Advice

Before advice	org.springframework.aop.BeforeAdvice; org.springframework.aop.MethodBeforeAdvice
After returning advice	org.springframework.aop.AfterReturningAdvice
After throwing advice	org.springframework.aop.ThrowsAdvice
After (finally) advice	?
Aroud advice	?

3 Config:

spring-aop-demo.xml

xml version="1.0" encoding="UTF-8"?>
>
<beans>

  <bean id="rect" class="org.springframework.aop.framework.ProxyFactoryBean">
    <property name="proxyInterfaces">
      <value>com.rainsoft.exercise1.aop.IShapevalue>
    property>
    <property name="target">
      <ref local="rectTarget"/>
    property>
    <property name="interceptorNames">
      <list>
        <value>timestampAdvisorvalue>
      list>
    property>
  bean>


  <bean id="rectTarget" class="com.rainsoft.exercise1.aop.Rectange">bean>


  <bean id="timestampAdvisor" class="org.springframework.aop.support.RegexpMethodPointcutAdvisor">
    <property name="advice">
      <ref local="timestampAdvice"/>
    property>
    <property name="pattern">
      <value>com\.rainsoft\.exercise1\.aop\.IShape\.drawvalue>
    property>
  bean>


  <bean id="timestampAdvice" class="com.rainsoft.exercise1.aop.TimestampMethodBeforeAdvice"/>
beans>

4 主程序

Main.java

package com.rainsoft.exercise1.aop;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.FileSystemXmlApplicationContext;

/**
 * Demo how to use Spring AOP
 * @author RainS.Yang
 * @version 1.0
 */
public class Main {
    public static void main(String[] args) {
        try {
            ApplicationContext ctx = new FileSystemXmlApplicationContext("spring-aop-demo.xml");
            IShape shape = (IShape)ctx.getBean("rect");
            shape.draw();
        }
        catch (Exception ex) {
            ex.printStackTrace();
        }
    }
}

5 运行结果

2006-12-05 01/32/03:entering method - draw
Rectange is drawn.