java – 构造函数参数解析

package com.springinaction.springidol;

public interface Performer {
    void perform();
}
package com.springinaction.springidol;

public class Juggler implements Performer {

    private int beanBags=3;
    private String name;

    public Juggler(){
    }

    public Juggler(String name,int beanBags){
        System.out.println("First constructor gets called");
        this.beanBags=beanBags;
        this.name=name;
    }

    public Juggler(int beanBags,String name){
        System.out.println("Second constructor gets called");
        this.beanBags=beanBags;
        this.name=name;
    }

    public void perform(){
    System.out.println("JUGGLING "+beanBags+name+" BEANBAGS");
    }
}

请查看下面我使用的spring配置文件的实例.

<?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-3.0.xsd">

<bean id="duke" class="com.springinaction.springidol.Juggler">
    <constructor-arg value="Jinesh" />
    <constructor-arg value="77" />
</bean>

在上面的场景中,调用的构造函数是第一个构造函数.但之后我稍微更改了xml文件并为两个参数添加了type属性.

<?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-3.0.xsd">

<bean id="duke" class="com.springinaction.springidol.Juggler">

<constructor-arg type="java.lang.String" value="Jinesh" />
<constructor-arg type="int" value="77" />

</bean>

</beans>

在上面的例子中,spring调用的构造函数是第二个构造函数.我不明白为什么spring决定调用第二个构造函数而不是第一个构造函数？在上面的例子中,当我们传递type属性时spring如何决定调用哪个构造函数？