Java Spring学习笔记----Bean的依赖注入（设值注入方式）1

Spring常用的两种依赖注入方式：一种是设值注入方式，利用Bean的setter方法设置Bean的属性值；另一种是构造注入，通过给Bean的构造方法传递参数来实现Bean的属性赋值；

1、设值注入方式

直接上代码例子，示例的树结构图如下

 Shape.java接口内容

package chapter3;

public interface Shape {
    public double area();//求形状的面积
}    

Circle.java内容：

package chapter3;

public class Circle implements Shape {

    double r;
    public double getR(){
        return this.r;
    }
    public void setR(double r){
        this.r=r;
    }
    
    @Override
    public double area() {
        // TODO Auto-generated method stub
        return Math.PI*Math.pow(r, 2);
    }

}

Rectangle.java内容

package chapter3;

public class Rectangle implements Shape {

    double width,height;
    
    public double getWidth(){
        return this.width;
    }
    public void setWidth(double width){
        this.width=width;
    }
    
    public double getHeight(){
        return this.height;
    }
    public void setHeight(double height){
        this.height=height;
    }
    
    @Override
    public double area() {
        // TODO Auto-generated method stub
        return width*height;
    }

}

AnyShape.java内容

package chapter3;

public class AnyShape {
    Shape shape;
    public void setShape(Shape shape) {this.shape=shape;}
    public Shape getShape(){return this.shape;}
    public void outputArea(){
        System.out.println("面积="+shape.area());
    }
}

Test.java内容

package chapter3;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.*;

public class Test {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        ApplicationContext context=new FileSystemXmlApplicationContext("src/myContext.xml");
        AnyShape shape=(AnyShape)context.getBean("anyShape");
        shape.outputArea();
        
        AnyShape shape2=(AnyShape)context.getBean("anyShape2");
        shape2.outputArea();
    }

}

xml配置文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
           http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">
           
           <bean id="myShape" class="chapter3.Circle">
           <property name="R">
           <value>2.5</value>
           </property>
           </bean>
           
           <bean id="myShape2" class="chapter3.Rectangle">
           <property name="height">
           <value>2</value>
           </property>
           <property name="width">
           <value>5</value>
           </property>
           </bean>
           
           <bean id="anyShape" class="chapter3.AnyShape">
           <property name="shape">
           <ref bean="myShape"/>
           </property>
           </bean>
           
            <bean id="anyShape2" class="chapter3.AnyShape">
           <property name="shape">
           <ref bean="myShape2"/>
           </property>
           </bean>

</beans>

 在配置文件中，每个Bean的id属性定义Bean的标识。查找和引用Bean是通过该标识进行的。Bean的class属性顶了Bean对应的类和路径名称。通过Bean的子元素property实现属性值的设置，它是通过调用相应属性的setter方法实现属性值的注入。标识为“anyshape”的Bean在设置shape的属性时通过<ref/>标签引用了标识为“myshape”的bean,也就是shape属性由标识为“myshape”的Bean决定的。