java - Spring "cannot be cast"

Question

我尝试使用 Eclipse 运行一个简单的 Spring(4.0.0 版本)程序。但我被困在一处。它说“无法施放”。

绘图.java

package org.spring;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Drawing {

    public static void main(String[] args) {
        ApplicationContext context= new ClassPathXmlApplicationContext("org/spring/spring.xml");
        Square myBean= (Square) context.getBean("square");
        myBean.paint();
    }

Square.java

package org.spring;

public class Square {
    public void paint() {
        System.out.println("Square Drawn");
    }
}

spring.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN 2.0//EN"  
"http://www.springframework.org/dtd/spring-beans-2.0.dtd"> 

<beans>
  <bean id="square" class="org.spring.Drawing">
  </bean>
</beans>

当我尝试执行它时，它会打印:

Exception in thread "main" java.lang.ClassCastException: org.spring.Drawing cannot be cast to org.spring.Square
    at org.spring.Drawing.main(Drawing.java:10)

Answer 1

这个

<bean id="square" class="org.spring.Drawing">

应该是

<bean id="square" class="org.spring.Square">

Drawing 不是 Square 的子类型，因此无法转换为 Square。