Spring—— 构造注入

　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