Autowire 在 Spring 中不工作

Question

我有以下 class:

public class Triangle implements Shape {
    /*@Autowired
     @Qualifier("A")*/

    private Point A;
    /*@Autowired
     @Qualifier("B")*/
    private Point B;
    /*@Autowired
     @Qualifier("C")*/
    private Point C;

    private static AtomicInteger id = new AtomicInteger();

    private int ownId;
    private int beanAttribute;
    @SuppressWarnings("unused")
    private int secondaryId;
    private String constructor = "Simple type --";

    private static final String NAME = "triangle";

    Triangle() {
        System.out.println("Triangle created without a secondaryId \n");
        secondaryId = -1;

    }

    Triangle(int secondaryId) {
        this.secondaryId = secondaryId;
        this.ownId = id.addAndGet(1);
    }

    Triangle(int secondaryId, String constructor) {
        this.secondaryId = secondaryId;
        this.ownId = id.addAndGet(1);
        this.constructor = constructor;
    }

    public Point getA() {
        return A;
    }

    public void setA(Point a) {
        A = a;
    }

    public Point getB() {
        return B;
    }

    public void setB(Point b) {
        B = b;
    }

    public Point getC() {
        return C;
    }

    public void setC(Point c) {
        C = c;
    }

    public int getOwnId() {
        return ownId;
    }
}

使用以下 XML 配置：

<beans>
<bean id="triangleDouble" class="draw.Triangle"
     scope="prototype" autowire="byName">
    <constructor-arg index="1" value="Double type ++" />
    <constructor-arg index="0" value="0" />
    <property name="beanAttribute" value="2" />
</bean>

<bean id="triangleSimple" class="draw.Triangle"
 scope="prototype" autowire="byName">
    <constructor-arg value="1" />
    <property name="beanAttribute" value="1" />
</bean>

<bean id="A" class="draw.Point">
    <property name="x" value="1" />
    <property name="y" value="2" />
</bean>

<bean id="B" class="draw.Point">
    <property name="x" value="2" />
    <property name="y" value="3" />
</bean>

<bean id="C" class="draw.Point">
    <property name="x" value="3" />
    <property name="y" value="4" />
</bean>

</beans>

问题是自动装配不工作。如果我设置 <property name="A" ref="A"/> 等，将不会出现 NullPointerException 并且我可以访问 Point.x 或 Point.y，因此代码编写正确，但如果我按名称自动装配，自动装配将不起作用并且当我尝试从 Triangle 访问 Point.x 时，我得到一个 java.lang.NullPointerException.

我尝试将 class 成员 A、B、C 设置为 @Autowire，都设置为 @Autowire 和 @Qualifier("A")，并且根本没有注释，但仍然没用。

Answer 1

你的程序运行后的错误：

Bean property 'beanAttribute' is not writable or has an invalid setter method. Does the parameter type of the setter match the return type of the getter?

<context:annotation-config />
<bean id="triangleDouble" bean id="triangleDouble" class="draw.Triangle"
         scope="prototype" autowire="byName">
        <constructor-arg index="1" value="Double type ++" />
        <constructor-arg index="0" value="0" />
        <property name="beanAttribute" value="2" />
</bean>

您错过了 beanAttribute.Add 的 setter 方法，它应该有效。

有关详细信息，请参阅 setter-injection

Answer 2

将您的 Point bean 名称重命名为小写，并将 'setA()'、'setB' 等设置器添加到三角形 class。它会解决问题。

问题是您没有遵循 JavaBeans 约定。

Autowire 在 Spring 中不工作

Autowire not working in Spring

java

xml

spring

autowired