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Spring doc for Autowiring by constructor 说它与 byType 相同，但用于构造函数参数。

如果是这样，那么为什么以下程序不会失败：

配置文件

<bean id="traingle" class="org.practise.autowiring.Triangle" autowire="constructor" />

<bean id="pointA" class="org.practise.autowiring.Point">
    <property name="x" value="0"/>
    <property name="y" value="10"/>
</bean>

<bean id="pointB" class="org.practise.autowiring.Point">
    <property name="x" value="220"/>
    <property name="y" value="330"/>
</bean>

<bean id="pointC" class="org.practise.autowiring.Point">
    <property name="x" value="40"/>
    <property name="y" value="60"/>
</bean>

在上述情况下，我尝试在以下类中注入 3 个相同类型（Point）的 bean：

    public class Triangle {
    private Point pointA;
    private Point pointB;
    private Point pointC;

    public Triangle(Point pointA, Point pointB, Point pointC) {
        this.pointA = pointA;
        this.pointB = pointB;
        this.pointC = pointC;
    }
    public Point getPointA() {
        return pointA;
    }
    public void setPointA(Point pointA) {
        this.pointA = pointA;
    }
    public Point getPointB() {
        return pointB;
    }
    public void setPointB(Point pointB) {
        this.pointB = pointB;
    }
    public Point getPointC() {
        return pointC;
    }
    public void setPointC(Point pointC) {
        this.pointC = pointC;
    }


    public void draw() {
        System.out.println("Point A: " + getPointA().getX() + ", " + getPointA().getY());
        System.out.println("Point B: " + getPointB().getX() + ", " + getPointB().getY());
        System.out.println("Point C: " + getPointC().getX() + ", " + getPointC().getY());
    }
}

观点

public class Point {
private int x;
private int y;

public int getX() {
    return x;
}
public void setX(int x) {
    this.x = x;
}
public int getY() {
    return y;
}
public void setY(int y) {
    this.y = y;
}

}

执行代码：

public static void main(String[] args) {
    ApplicationContext context = new ClassPathXmlApplicationContext("org/practise/autowiring/spring-autowiring.xml");
    Triangle triangle = (Triangle) context.getBean(Triangle.class);
    triangle.draw();
}

它传递并打印以下内容：

Aug 18, 2013 2:04:56 PM org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@43ee1619: startup date [Sun Aug 18 14:04:56 PDT 2013]; root of context hierarchy
Aug 18, 2013 2:04:56 PM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [org/practise/autowiring/spring-autowiring.xml]
Aug 18, 2013 2:04:56 PM org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons
INFO: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@13c6395b: defining beans [traingle,pointA,pointB,pointC]; root of factory hierarchy
Point A: 0, 10
Point B: 220, 330
Point C: 40, 60

当我将接线类型更改为“byType”时，它会引发预期的异常。只有在上述情况下它才能正常工作。我正在使用 Spring 3.2

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