Spring在继承时创建两次子bean，并且从不创建父bean

<!-- 错误的示例 -->
<bean id="childBean" class="com.example.ChildBean" parent="parentBean"/>
<bean id="childBean" class="com.example.ChildBean" parent="parentBean"/> <!-- 重复定义 -->

@Configuration
@ComponentScan(basePackages = "com.example")
public class AppConfig {
}

<bean id="parentBean" class="com.example.ParentBean"/>
<bean id="childBean" class="com.example.ChildBean" parent="parentBean"/>

@Component
@Scope("singleton")
public class ChildBean extends ParentBean {
}

@Configuration
public class AppConfig {

    @Bean
    public ParentBean parentBean() {
        return new ParentBean();
    }

    @Bean
    public ChildBean childBean() {
        return new ChildBean(parentBean());
    }
}

public class ParentBean {
    // 父bean的属性和方法
}

public class ChildBean extends ParentBean {
    public ChildBean(ParentBean parentBean) {
        // 初始化子bean，可以使用父bean的实例
    }
    // 子bean的属性和方法
}