java - spring 通用应用程序事件无法到达目的地

Question

我有以下 Spring 架 bean 。这个想法是它保留某物的一个实例，并在某物发生变化时触发一个更改事件(同时提供旧值和新值):

public class Holder<T> implements ApplicationEventPublisherAware {
    private final Class<T> payloadType; //because java generics are incomplete
    private T curr; //latest value being held
    private ApplicationEventPublisher publisher; //spring context ref

    public Holder(Class<T> payloadType) {
        this.payloadType = payloadType;
    }

    public void change() throws Exception {
        T prev = curr;
        curr = payloadType.newInstance();
        publisher.publishEvent(new ContentsChangedEvent<>(prev, curr));
    }
}

然后我有一个监听器类对这些事件使用react:

@Named
public class Listener {

    @EventListener
    public void onChange(ContentsChangedEvent<Cat> event) {
        //never gets called
    }

    @EventListener
    public void onErasedChange(ContentsChangedEvent<?> event) {
        //does get called
    }
}

我的问题是通用(正确)事件监听器方法永远不会被调用(获得 Event<Cat> 的那个)，只有被删除的那个。

为了完整起见，这里是 spring context.xml

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans-4.2.xsd
       http://www.springframework.org/schema/context
       http://www.springframework.org/schema/context/spring-context-4.2.xsd">

    <context:annotation-config/>
    <context:component-scan base-package="net.radai"/>

    <bean id="holder" class="net.radai.Holder">
        <constructor-arg type="java.lang.Class" value="net.radai.Cat"/>
    </bean>
</beans>

我也把整件事都放在了 github - https://github.com/radai-rosenblatt/spring-events 上。它是一个 Maven 项目——你构建它，你会得到一个失败的测试。

我究竟做错了什么？

注意: 在实际用例中，我希望有多个这样的持有者，并迫使所有监听器以 Not Acceptable 方式丢弃与他们无关的事件

Answer 1

public class ContentsChangedEvent<T> extends ApplicationEvent{

    public ContentsChangedEvent(Holder<T> source, T prev, T curr) {
        super(source);
        this.prev = prev;
        this.curr = curr;
    }                                  

}   

//Holder class
public void change() {
        T prev = curr;
        try {
        curr = payloadType.newInstance();
        } catch (Exception e) {
            int g = 8;
        }
        publisher.publishEvent(new ContentsChangedEvent<T>(this, prev, curr));
 }

onChange 和 onErasedChange 都会被调用。