如果想要使用spring来实现依赖注入，需要几个重要的步骤：
1 定义主要的类和需要分离的属性。这里主要的类，是指程序的主要对象，在例子中是Juggler杂技员。而想要分离构造的属性，是它手中的袋子的数目beanBags。
2 配置bean.xml。通过配置文件，确定主要的类和属性之间的关系，以及实现类。
3 通过应用上下文，获取bean，并进行使用。
注入属性
实例代码：
1 表演者接口：Performer.java
package com.spring.test.action1;
public interface Performer {
void perform() throws PerformanceException;
}2 杂技员：Juggler，继承了表演者接口
package com.spring.test.action1;
public class Juggler implements Performer{
private int beanBags = ;
public Juggler(){
}
public Juggler(int beanBags){
this.beanBags = beanBags;
}
public void perform() throws PerformanceException {
System.out.println("Juggler "+beanBags+" beanBags");
}
}3 Spring配置文件：bean.xml
<?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="duke" class="com.spring.test.action1.Juggler">
<constructor-arg value=""/>
</bean>
</beans>
4 应用上下文获取指定的bean
package com.spring.test.action1; import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext; public class test {
public static void main(String[] args) {
ApplicationContext ctx = new ClassPathXmlApplicationContext("bean.xml");
Performer performer = (Performer)ctx.getBean("duke");
try {
performer.perform();
} catch (PerformanceException e) {
e.printStackTrace();
}
}
}
执行结果如下：
Juggler beanBags
注入对象
1 例如，上面的杂技演员不仅仅会仍袋子，还会表演诗歌，那么诗歌这个对象就需要注入到表演者的构造函数中，可以如下表示会朗诵诗歌的杂技演员：PoeticJuggler
package com.spring.test.action1;
public class PoeticJuggler extends Juggler{
private Poem poem;
public PoeticJuggler(Poem poem){
super();
this.poem = poem;
}
public PoeticJuggler(int beanBags,Poem poem){
super(beanBags);
this.poem = poem;
}
public void perform() throws PerformanceException {
super.perform();
System.out.println("While reciting...");
poem.recite();
}
}2 诗歌对象：Sonnet29
package com.spring.test.action1;
public class Sonnet29 implements Poem{
private static String lines = "嘛咪嘛咪哄";
public Sonnet29() {
}
public void recite() {
System.out.println(lines);
}
}3 Bean.xml配置文件如下
<?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="duke" class="com.spring.test.action1.Juggler">
<constructor-arg value=""/>
</bean>
<bean id="sonnet29" class="com.spring.test.action1.Sonnet29"/>
<bean id="poeticDuke" class="com.spring.test.action1.PoeticJuggler">
<constructor-arg value=""/>
<constructor-arg ref="sonnet29"/>
</bean>
</beans>
4 主要的执行代码，通过应用上下文获取制定的bean
package com.spring.test.action1; import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext; public class test {
public static void main(String[] args) {
ApplicationContext ctx = new ClassPathXmlApplicationContext("bean.xml");
// Performer performer = (Performer)ctx.getBean("duke");
Performer performer1 = (Performer)ctx.getBean("poeticDuke");
try {
// performer.perform();
performer1.perform();
} catch (PerformanceException e) {
e.printStackTrace();
}
}
}
5 执行结果如下
一月 , :: 下午 org.springframework.context.support.AbstractApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@35bf8de1: startup date [Sat Jan :: CST ]; root of context hierarchy
一月 , :: 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
信息: Loading XML bean definitions from class path resource [bean.xml]
一月 , :: 下午 org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons
信息: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@3401a0ad: defining beans [duke,sonnet29,poeticDuke]; root of factory hierarchy
Juggler beanBags
While reciting...
嘛咪嘛咪哄