spring IOC一个类有多个构造器，用构造器注入怎么解决匹配问题

本是古典何须时尚 2022-04-10 03:00 247阅读 0赞

Car 类写入两个构造器（参数不同）

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

配置文件如下

<?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>
        
        </bean>
        
        <bean id="car2" class="com.beans.Car">
        <constructor-arg value="Boma"></constructor-arg>
        <constructor-arg value="ChangSha"></constructor-arg>
        <constructor-arg value="240"></constructor-arg>
        </bean>
        
        
    </beans>

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=(Car)ctx.getBean("car");
            System.out.println(car);
            
            Car car2=(Car)ctx.getBean("car2");
            System.out.println(car2);
    	}
    
    }

运行结果如图所示，都匹配到了第一个构造器。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3Nzc0MTcx_size_16_color_FFFFFF_t_70]

那么怎么让第二个bean匹配到第二个构造器呢?  
加一下属性类型就可以了，如下图

再次运行。it is ok.  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3Nzc0MTcx_size_16_color_FFFFFF_t_70 1]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3Nzc0MTcx_size_16_color_FFFFFF_t_70]: /images/20220403/851e9d537ee145ce974f2fd9d40eaa0c.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3Nzc0MTcx_size_16_color_FFFFFF_t_70 1]: /images/20220403/2087e097f95a4e189c48470ffe9d7b1a.png