org.bushe.swing.event.annotation.VetoSubscriber Maven / Gradle / Ivy

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A simple but powerful publish-subscribe API that is based on class semantics and/or string (topic) matching.

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package org.bushe.swing.event.annotation;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import org.bushe.swing.event.EventService;
import org.bushe.swing.event.EventServiceLocator;
import org.bushe.swing.event.ThreadSafeEventService;

/**
 * An Annotation for adding VetoListener subscriptions to EventService Events.
 * 
 * This annotation simplifies much of the repetitive boilerplate used for adding veto listeners
 * (which in EventBus 2.0 will be called VetoSubscribers, thus this annotation name difference)
 * to EventService Events.  Example:
 * 

 * 
 * public class MyAppController {
 *   public MyAppController {
 *       AnnotationProcessor.process(this);//this line can be avoided with a compile-time tool or an Aspect
 *   }
 *   @EventSubscriber(eventClass=AppAppClosingEvent.class)
 *   public void onAppClosingEvent(AppClosingEvent appClosingEvent) {
 *      //close connections, close windows
 *   }
 * }
 *
 * public class MyDocumentController {
 *   @VetoSubscriber(eventClass=AppAppClosingEvent.class)
 *   public boolean ensureDocumentIsSaved(AppAppClosingEvent appClosingEvent) {
 *      if (docHasUnsavedChanges()) {
 *         boolean answer = MyModalDialog.show("Are you sure you want to close and lose your changes?");
 *         if (answer == StandardButtonValues.Cancel) {
 *            //stop processing this event
 *            return true;
 *         }
 *      }
 *      //It's OK to close
 *      return false;
 *   }
 * }
 * 
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface VetoSubscriber {
   /** The class to subscribe to, if not specified, a subscription is created for the type of the method parameter. */
   public abstract Class eventClass() default UseTheClassOfTheAnnotatedMethodsParameter.class;

   /** Determines the order in which this veto subscriber is called, default is FIFO.*/
   public abstract int priority() default 0;

   /** Whether or not to subscribe to the exact class or a class hierarchy, defaults to class hierarchy (false). */
   public abstract boolean exact() default false;

   /** Whether to subscribe weakly or strongly. */
   public abstract ReferenceStrength referenceStrength() default ReferenceStrength.WEAK;

   /** The event service to subscribe to, default to the EventServiceLocator.SERVICE_NAME_EVENT_BUS. */
   public abstract String eventServiceName() default EventServiceLocator.SERVICE_NAME_EVENT_BUS;

   /**
    * Whether or not to autocreate the event service if it doesn't exist on subscription, default is true. If the
    * service needs to be created, it must have a default constructor.
    */
   public abstract Class autoCreateEventServiceClass() default ThreadSafeEventService.class;
}