【Spring实战】——6内部Bean
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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