【Spring实战】—— 6 内部Bean

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本篇文章讲解了Spring的通过内部Bean设置Bean的属性。
　　类似内部类，内部Bean与普通的Bean关联不同的是：
　　1 普通的Bean，在其他的Bean实例引用时，都引用同一个实例。
　　2 内部Bean，每次引用时都是新创建的实例。

　　鉴于上述的场景，内部Bean是一个很常用的编程模式。

　　下面先通过前文所述的表演者的例子，描述一下主要的类：

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();    }}

　　其他代码，如下：

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

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

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

　　如果使用 设值注入 需要设定属性和相应的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>

　　如果使用 构造注入 需要构造函数。

<?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>

　　应用上下文使用方法：

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();    }}

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