【Spring實戰】—— 6 內部Bean

本篇文章講解了Spring的經過內部Bean設置Bean的屬性。

　　相似內部類，內部Bean與普通的Bean關聯不一樣的是：

　　1 普通的Bean，在其餘的Bean實例引用時，都引用同一個實例。

　　2 內部Bean，每次引用時都是新建立的實例。

　　鑑於上述的場景，內部Bean是一個很經常使用的編程模式。

　　下面先經過前文所述的表演者的例子，描述一下主要的類：

package com.spring.test.setter; import com.spring.test.action1.PerformanceException; import com.spring.test.action1.Performer; public class Instrumentalist implements Performer{ private String song; private int age; private Instrument instrument; public int getAge() { return age; } public void setAge(int age) { this.age = age; } public String getSong() { return song; } public void setSong(String song) { this.song = song; } public Instrument getInstrument() { return instrument; } public void setInstrument(Instrument instrument) { this.instrument = instrument; } public Instrumentalist(){} public Instrumentalist(String song,int age,Instrument instrument){ this.song = song; this.age = age; this.instrument = instrument; } public void perform() throws PerformanceException { System.out.println("Instrumentalist age:"+age); System.out.print("Playing "+song+":"); instrument.play(); } }

　　其餘代碼，以下：

package com.spring.test.setter; public interface Instrument { public void play(); }

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package com.spring.test.setter; public class Saxophone implements Instrument { public Saxophone(){} public void play() { System.out.println("TOOT TOOT TOOT"); } }

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package com.spring.test.action1; public interface Performer { void perform() throws PerformanceException; }

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　　若是使用 設值注入 須要設定屬性和相應的setter getter方法。

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.springframework.org/schema/beans" xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
     <bean id="kenny" class="com.spring.test.setter.Instrumentalist">
         <property name="song" value="Jingle Bells" />
         <property name="age" value="25" />
         <property name="instrument">
             <bean class="com.spring.test.setter.Saxophone"/>
         </property>
     </bean>
</beans>

　　若是使用 構造注入 須要構造函數。

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.springframework.org/schema/beans" xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
     <bean id="kenny-constructor" class="com.spring.test.setter.Instrumentalist">
         <constructor-arg value="Happy New Year"/>
         <constructor-arg value="30"/>
         <constructor-arg>
             <bean class="com.spring.test.setter.Saxophone"/>
         </constructor-arg>
     </bean>
</beans>

　　應用上下文使用方法：

public class test { public static void main(String[] args) throws PerformanceException { ApplicationContext ctx = new ClassPathXmlApplicationContext("bean.xml"); Instrumentalist performer = (Instrumentalist)ctx.getBean("kenny"); performer.perform(); Instrumentalist performer2 = (Instrumentalist)ctx.getBean("kenny-constructor"); performer2.perform(); } }