我有一个名为circle的简单类,它有一个名为center的属性,我有一个名为circle的简单类,它有一个名为center的属性,我在其上应用了@Resource注释来注入(inject)来自spring.xml的依赖项,但不知何故中心值不是从 spring.xml 注入(inject)的,这就是为什么我在获取值时遇到空指针异常。 我有一个在 xml 中定义的 bean,其名称与圆的属性名称相同
//Circle class:
package org.devesh.learning.spring;
import javax.annotation.Resource;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
public class Circle implements Shape {
private Point center;
@Override
public void draw() {
System.out.println("Circle drawn");
System.out.println("Circle center is : "+ center.getX() + "," + center.getY());
}
public Point getCenter() {
return center;
}
//@Autowired
//@Qualifier("circle related")
@Resource
public void setCenter(Point center) {
this.center = center;
}
}
Point class:
package org.devesh.learning.spring;
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;
}
}
spring.xml:
<?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 https://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context/spring-context-3.2.xsd
https://www.springframework.org/schema/context/spring-context-3.2.xsd"
xmlns:context="http://www.springframework.org/schema/context/spring-context-3.2.xsd">
<bean id="circle" class="org.devesh.learning.spring.Circle">
</bean>
<bean id ="pointA" class="org.devesh.learning.spring.Point">
<property name="x" value="${pointA.pointX}"></property>
<property name="y" value="${pointA.pointY}"></property>
</bean>
<bean id = "center" class="org.devesh.learning.spring.Point">
<property name="x" value="20"></property>
<property name="y" value="0"></property>
</bean>
<bean id = "pointC" class="org.devesh.learning.spring.Point">
<property name="x" value="-20"></property>
<property name="y" value="0"></property>
</bean>
<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="locations" value="pointconfig.properties"></property>
</bean>
</beans>
最佳答案
你有多个相同点类型的bean,通过它的ID注入(inject)中心, @Resource(名称=“中心”)
关于java - setter方法上使用@Resource注解使用getter方法获取值时返回空指针异常,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/58145791/