本文讲解了构造注入以及spring的基本使用方式，通过一个杂技演员的例子，讲述了依赖注入属性或者对象的使用方法。
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 = 3; 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="15"/> </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 15 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="15"/> </bean> <bean id="sonnet29" class="com.spring.test.action1.Sonnet29"/> <bean id="poeticDuke" class="com.spring.test.action1.PoeticJuggler"> <constructor-arg value="15"/> <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 24, 2015 4:40:46 下午 org.springframework.context.support.AbstractApplicationContext prepareRefresh 信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@35bf8de1: startup date [Sat Jan 24 16:40:46 CST 2015]; root of context hierarchy 一月 24, 2015 4:40:46 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions 信息: Loading XML bean definitions from class path resource [bean.xml] 一月 24, 2015 4:40:46 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 15 beanBags While reciting... 嘛咪嘛咪哄
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