java - Autowiring 在 Spring 中不起作用

Question

我有以下类(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 Autowiring 不工作。如果我设置 <property name="A" ref="A"/>等等，不会有 NullPointerException，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 Autowiring ， Autowiring 将不起作用，当我尝试从 Triangle 访问 Point.x 时，我得到一个java.lang.NullPointerException .

我试图用 @Autowire 设置类成员 A、B、C , 都带有 @Autowire和 @Qualifier("A")并且根本没有注释，但它仍然不起作用。

Answer 1

运行程序后的错误:

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 的 setter 方法。添加相同的方法，它应该可以工作。

有关更多信息，请参阅 setter-injection