Guava EventBus:如何从事件处理程序返回结果

import com.google.common.eventbus.EventBus;
import com.google.common.eventbus.Subscribe;

public class Main {
  public static void main(String[] args) {
    EventBus eventBus = new EventBus();
    eventBus.register(new MyEventProcessor());

    eventBus.post(new MyEvent());
  }

  private static class MyEventProcessor implements EventBus.Handler {
    @Subscribe
    public void handleMyEvent(MyEvent event) {
      System.out.println("Received MyEvent: " + event.getMessage());
    }
  }

  public static class MyEvent {
    private String message;

    public MyEvent(String message) {
      this.message = message;
    }

    public String getMessage() {
      return message;
    }
  }
}

import com.google.common.eventbus.EventBus;
import com.google.common.eventbus.Subscribe;

public class Main {
  public static void main(String[] args) {
    EventBus eventBus = new EventBus();
    eventBus.register(new MyEventProcessor());

    eventBus.post(new MyEvent("Hello, World!"));
  }

  private static class MyEventProcessor implements EventBus.Handler {
    @Subscribe(returns = RETURN_CURRENT_VALUE)
    public String handleMyEvent(MyEvent event) {
      return event.getMessage();
    }
  }

  public static class MyEvent {
    private String message;

    public MyEvent(String message) {
      this.message = message;
    }

    public String getMessage() {
      return message;
    }
  }
}