Reusing annotations by creating meta annotations

Question

I am just wondering whether we can create a meta-annotation and reuse it everywhere. For example, I have an annotation like so:

@QueueBinding(value = @Queue, exchange = @Exchange(value = "MY_FANOUT_EXCHANGE", type = ExchangeTypes.FANOUT))

I need to use it in multiple places. I just want to simplify it something like:

@MyFanoutExchangeBinding = @QueueBinding(value = @Queue, exchange = @Exchange(value = "MY_FANOUT_EXCHANGE", type = ExchangeTypes.FANOUT))

and then use the @MyFanoutExchangeBinding on methods everywhere. If I understand annotations correctly, its not possible. Or is it?

Answer 1

元注释在此上下文中不起作用，因为@RabbitListener bindings属性是QueueBinding[]且注释没有继承。

要实现它需要一个自定义的RabbitListenerAnnotationBeanPostProcessor，但由于它不能以通用的方式完成，我认为它不能成为框架的一部分，至少在你描述的方式。

我们可能会以其他方式减少样板;随意打开JIRA issue，我们可以看一看可能的情况。

修改

收到JIRA Issue之后我又考虑了一些问题，您可以使用自定义侦听器注释获得所需结果，并使用@RabbitListener进行元注释...

@Target({ElementType.TYPE, ElementType.METHOD, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@RabbitListener(bindings = @QueueBinding(
        value = @Queue,
        exchange = @Exchange(value = "test.metaFanout", type = ExchangeTypes.FANOUT, autoDelete = "true")))
public @interface MyAnonFanoutListener {
}

public static class MetaListener {

    @MyAnonFanoutListener
    public void handle1(String foo) {
        ...
    }

    @MyAnonFanoutListener
    public void handle2(String foo) {
        ...
    }

}

每个侦听器都会获得一个绑定到扇出交换的匿名自动删除队列。