java - 如何为java自定义注释提供属性占位符支持

Question

我创建了一个自定义 Java 注释并具有某些属性。如何支持字符串属性的属性占位符？

例如:

Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface PublishEvent {

    public EventStore eventStore();
    public boolean isPersistent() default false;
    public String channelName();


}

我想用作:

@PublishEvent(channelName="${rabbit.event.default}")
public void someMethod(){}

其中rabbit.event.default是application.properties文件中定义的属性的键。我希望将属性键替换为值，就像 spring 的 @Value 注释一样。

我正在使用Spring AOP来拦截注释并进行处理。

Answer 1

我使用org.springframework.util.StringValueResolver#resolveStringValue解析占位符值的方法。也许下面的示例代码可以帮助您:

@Configuration
public class PublishEventConfiguration implements ApplicationContextAware, EmbeddedValueResolverAware {
  private ApplicationContext context;
  private StringValueResolver resolver;

  @Override
  public void setApplicationContext(ApplicationContext context) throws BeansException {
    this.context = context;
  }

   @Override
  public void setEmbeddedValueResolver(StringValueResolver resolver) {
    this.resolver = resolver;
  }


  @PostConstruct
  public void init() throws Exception {
    Collection<Object> publishEvents = context.getBeansWithAnnotation(PublishEvent.class).values();
    for (Object v : publishEvents) {
      PublishEvent cfg = v.getClass().getAnnotation(PublishEvent.class);
      String channelName = resolver.resolveStringValue(cfg.channelName());
    }
  }
}