spring IOC构造器注入使用

- 日理万妓 2022-04-10 02:59 244阅读 0赞

运行主类

package com.beans;
    
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    public class Main {
    
    	public static void main(String[] args) {
    		
           //1.创建spring的IOC容器对象
    		//ApplicationContext 代表IOC容器 是 BeanFactory 接口的子接口
    		
    		// ClassPathXmlApplicationContext: 是 ApplicationContext的实现类，从类路径下来加载配置文件
            ApplicationContext ctx=new ClassPathXmlApplicationContext("applicationContext.xml");
            
            //2.从IOC容器中获取bean实例
            //利用id定位到IOC容器中的bean
          
            Car car=ctx.getBean(car);
            System.out.println(car);
    	}
    
    }

Car类

package com.beans;
    
    public class Car {
    	   private String brand;
    	   private String corp;
           private double price;
           private int maxSpeed;
           
           public Car(String brand, String corp, double price, int maxSpeed) {
       		super();
       		this.brand = brand;
       		this.corp = corp;
       		this.price = price;
       		this.maxSpeed = maxSpeed;
       	}
           @Override
       	public String toString() {
       		return "Car [brand=" + brand + ", corp=" + corp + ", price=" + price + ", maxSpeed=" + maxSpeed + "]";
       	}
    
    }

xml配置文件，主要注意的地方是这个标签没有name属性，所以一定要按构造器的属性的先后顺序编写好配置文件。  
比如第一个属性String brand;

<constructor-arg value="Audi" index="0"></constructor-arg>

对应好位置就可以了。

<?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.xsd">
    
        
        
    
        
        <bean id="car" class="com.beans.Car">
        <constructor-arg value="Audi" index="0"></constructor-arg>
        <constructor-arg value="ShangHai" index="1"></constructor-arg>
        <constructor-arg value="30000" index="2"></constructor-arg>
        <constructor-arg value="200" index="3"></constructor-arg>
        </bean>
        
        
    </beans>