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