SPRING IN ACTION 第4版笔记-第一章-003-AOP介绍

一、目标

要在BraveKnight调用embarkOnQuest()前后各做一些处理(调用Minstrel的方法)

二、

1.minstrel.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:aop="http://www.springframework.org/schema/aop"
  xsi:schemaLocation="http://www.springframework.org/schema/aop 
      http://www.springframework.org/schema/aop/spring-aop.xsd
        http://www.springframework.org/schema/beans 
      http://www.springframework.org/schema/beans/spring-beans.xsd">

  <bean id="knight" class="chapter01.sia.knights.BraveKnight">
    <constructor-arg ref="quest" />
  </bean>

  <bean id="quest" class="chapter01.sia.knights.SlayDragonQuest">
    <constructor-arg value="#{T(System).out}" />
  </bean>

  <bean id="minstrel" class="chapter01.sia.knights.Minstrel">
    <constructor-arg value="#{T(System).out}" />
  </bean>

  <aop:config>
    <aop:aspect ref="minstrel">
      <aop:pointcut id="embark"
          expression="execution(* *.embarkOnQuest(..))"/>
        
      <aop:before pointcut-ref="embark" 
          method="singBeforeQuest"/>

      <aop:after pointcut-ref="embark" 
          method="singAfterQuest"/>
    </aop:aspect>
  </aop:config>
  
</beans>

分析：

(1)首先声明xsi:schemaLocation="http://www.springframework.org/schema/aop

(2)把Minstrel.java声明为bean，给spring管理

(3)声明<aop:config><aop:aspect，指定到ref="minstrel"

(4)声明<aop:pointcut，指定在这些方法中aop,expression="execution(* *.embarkOnQuest(..))"

(5)声明<aop:before、<aop:after

2.Minstrel

package chapter01.sia.knights;

import java.io.PrintStream;

public class Minstrel {

  private PrintStream stream;
  
  public Minstrel(PrintStream stream) {
    this.stream = stream;
  }

  public void singBeforeQuest() {
    stream.println("Fa la la, the knight is so brave!");
  }

  public void singAfterQuest() {
    stream.println("Tee hee hee, the brave knight " +
            "did embark on a quest!");
  }

}

3.KnightMain

public class KnightMain {

  public static void main(String[] args) throws Exception {
    //ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath:knight.xml");
    ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath:minstrel.xml");
    Knight knight = context.getBean(Knight.class);
    knight.embarkOnQuest();
    context.close();
  }

}

4.运行结果

三月 01, 2016 10:49:57 上午 org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@3f3471d: startup date [Tue Mar 01 10:49:57 CST 2016]; root of context hierarchy
三月 01, 2016 10:49:57 上午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
信息: Loading XML bean definitions from class path resource [minstrel.xml]
Fa la la, the knight is so brave!
Embarking on quest to slay the dragon!
Tee hee hee, the brave knight did embark on a quest!
三月 01, 2016 10:49:58 上午 org.springframework.context.support.ClassPathXmlApplicationContext doClose
信息: Closing org.springframework.context.support.ClassPathXmlApplicationContext@3f3471d: startup date [Tue Mar 01 10:49:57 CST 2016]; root of context hierarchy