SPRING IN ACTION 第4版笔记-第二章Wiring Beans-005-<constructor-arg>和c-namespace

1.

 package soundsystem;

 public class SgtPeppers implements CompactDisc {

   private String title = "Sgt. Pepper's Lonely Hearts Club Band";
   private String artist = "The Beatles";

   public void play() {
     System.out.println("Playing " + title + " by " + artist);
   }

 }

2.

 package soundsystem;
 import org.springframework.beans.factory.annotation.Autowired;

 public class CDPlayer implements MediaPlayer {
   private CompactDisc cd;

   @Autowired
   public CDPlayer(CompactDisc cd) {
     this.cd = cd;
   }

   public void play() {
     cd.play();
   }

 }

一、-<constructor-arg>

<?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">

  <bean id="compactDisc" class="soundsystem.SgtPeppers" />

  <bean id="cdPlayer" class="soundsystem.CDPlayer">
    <constructor-arg ref="compactDisc" />
  </bean>

</beans>

二、c-namespace(3.0开始有)

(1)指定参数名称

 <?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:c="http://www.springframework.org/schema/c"
   xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

   <bean id="compactDisc" class="soundsystem.SgtPeppers" />

   <bean id="cdPlayer" class="soundsystem.CDPlayer"
         c:cd-ref="compactDisc" />

 </beans>

(2)指定参数顺序

<bean id="cdPlayer" class="soundsystem.CDPlayer"
c:_0-ref="compactDisc" />

(3)如查构造函数只有一个参数，则可以连顺序都不用指定

<bean id="cdPlayer" class="soundsystem.CDPlayer"
c:_-ref="compactDisc" />