Question

我有以下课程：

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>

问题是自动装配不起作用。如果我设置<property name="A" ref="A"/>等，就没有NullPointerException，我可以访问Point.x或Point.y，所以代码写得正确，但如果我通过名称自动装配，自动装配将无法工作，何时我会尝试从Triangle访问Point.x我得到一个java.lang.NullPointerException。

我尝试使用@Autowire设置班级成员A，B，C，@Autowire和@Qualifier("A")并且根本没有注释，但它仍然没有工作

Answer 1

运行程序后的错误：

Bean属性＆＃39; beanAttribute＆＃39;不可写或具有无效的setter 方法。 setter的参数类型是否与返回类型匹配吸气鬼？

<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>

你错过了beanAttribute的setter方法。添加相同的方法，它应该可以工作。

有关详细信息，请参阅setter-injection

Answer 2

将Point bean名称重命名为小写，并将“setA（）”，“setB”等setter添加到Triangle类中。它将解决问题。

麻烦的是你没有遵循JavaBeans惯例。

Autowire不在Spring工作

2 个答案: