Get rid of visitor pattern for event handling

@EventListener is used for handler methods instead of implementing
a visitor interface.

src/main/java/de/thm/arsnova/cache/CacheBusterImpl.java

@@ -19,6 +19,7 @@ package de.thm.arsnova.cache;
 
 import de.thm.arsnova.event.*;
 import org.springframework.cache.annotation.CacheEvict;
+import org.springframework.context.event.EventListener;
 import org.springframework.stereotype.Component;
 
 /**
@@ -26,105 +27,29 @@ import org.springframework.stereotype.Component;
  * caches, e.g, for a specific session.
  */
 @Component
-public class CacheBusterImpl implements CacheBuster, ArsnovaEventVisitor {
+public class CacheBusterImpl implements CacheBuster {
 
 	@CacheEvict(value = "statistics", allEntries = true)
-	@Override
-	public void visit(NewCommentEvent event) { }
+	@EventListener
+	public void handleNewComment(NewCommentEvent event) { }
 
 	@CacheEvict(value = "statistics", allEntries = true)
-	@Override
-	public void visit(DeleteCommentEvent event) { }
-
-	@Override
-	public void visit(NewQuestionEvent event) { }
-
-	@Override
-	public void visit(UnlockQuestionEvent event) { }
-
-	@Override
-	public void visit(UnlockQuestionsEvent newQuestionsEvent) { }
-
-	@Override
-	public void visit(LockQuestionEvent lockQuestionEvent) { }
-
-	@Override
-	public void visit(LockQuestionsEvent lockQuestionsEvent) { }
+	@EventListener
+	public void handleDeleteComment(DeleteCommentEvent event) { }
 
 	@CacheEvict(value = "answerlists", key = "#event.content.id")
-	@Override
-	public void visit(NewAnswerEvent event) { }
-
-	@Override
-	public void visit(DeleteAnswerEvent event) { }
-
-	@Override
-	public void visit(DeleteQuestionEvent event) { }
-
-	@Override
-	public void visit(DeleteAllQuestionsEvent event) { }
-
-	@Override
-	public void visit(DeleteAllQuestionsAnswersEvent event) { }
-
-	@Override
-	public void visit(DeleteAllPreparationAnswersEvent event) { }
-
-	@Override
-	public void visit(DeleteAllLectureAnswersEvent event) { }
-
-	@Override
-	public void visit(NewFeedbackEvent event) { }
-
-	@Override
-	public void visit(DeleteFeedbackForRoomsEvent event) { }
-
-	@Override
-	public void visit(StatusRoomEvent event) { }
+	@EventListener
+	public void handleNewAnswer(NewAnswerEvent event) { }
 
 	@CacheEvict(value = "statistics", allEntries = true)
-	@Override
-	public void visit(ChangeScoreEvent changeLearningProgress) { }
-
-	@Override
-	public void visit(PiRoundDelayedStartEvent piRoundDelayedStartEvent) { }
-
-	@Override
-	public void visit(PiRoundEndEvent piRoundEndEvent) { }
-
-	@Override
-	public void visit(PiRoundCancelEvent piRoundCancelEvent) { }
-
-	@Override
-	public void visit(PiRoundResetEvent piRoundResetEvent) { }
+	@EventListener
+	public void handleChangeScore(ChangeScoreEvent changeLearningProgress) { }
 
 	@CacheEvict(value = "statistics", allEntries = true)
-	@Override
-	public void visit(NewRoomEvent newSessionEvent) { }
+	@EventListener
+	public void handleewRoom(NewRoomEvent newSessionEvent) { }
 
 	@CacheEvict(value = "statistics", allEntries = true)
-	@Override
-	public void visit(DeleteRoomEvent deleteSessionEvent) { }
-
-	@Override
-	public void visit(LockVoteEvent lockVoteEvent) { }
-
-	@Override
-	public void visit(LockVotesEvent lockVotesEvent) { }
-
-	@Override
-	public void visit(UnlockVoteEvent unlockVoteEvent) { }
-
-	@Override
-	public void visit(UnlockVotesEvent unlockVotesEvent) { }
-
-	@Override
-	public void visit(FeatureChangeEvent featureChangeEvent) { }
-
-	@Override
-	public void visit(LockFeedbackEvent lockFeedbackEvent) { }
-
-	@Override
-	public void visit(FlipFlashcardsEvent flipFlashcardsEvent) { }
-
+	@EventListener
+	public void handleDeleteRoom(DeleteRoomEvent deleteSessionEvent) { }
 }

src/main/java/de/thm/arsnova/cache/CacheBusterListener.java

-/*
- * This file is part of ARSnova Backend.
- * Copyright (C) 2012-2018 The ARSnova Team and Contributors
- *
- * ARSnova Backend is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * ARSnova Backend is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- */
-package de.thm.arsnova.cache;
-
-import de.thm.arsnova.event.ArsnovaEvent;
-import de.thm.arsnova.event.ArsnovaEventVisitor;
-import org.springframework.beans.factory.annotation.Autowired;
-import org.springframework.context.ApplicationListener;
-import org.springframework.stereotype.Component;
-
-/**
- * Listener registration for the cache buster.
- *
- * Note that this class is necessary in order for the annotations to work.
- */
-@Component
-public class CacheBusterListener implements ApplicationListener<ArsnovaEvent> {
-
-	@Autowired
-	private CacheBuster cacheBuster;
-
-	@Override
-	public void onApplicationEvent(ArsnovaEvent event) {
-		event.accept((ArsnovaEventVisitor) cacheBuster);
-	}
-
-}

src/main/java/de/thm/arsnova/config/AppConfig.java

@@ -34,7 +34,6 @@ import de.thm.arsnova.web.PathApiVersionContentNegotiationStrategy;
 import de.thm.arsnova.web.ResponseInterceptorHandler;
 import de.thm.arsnova.websocket.ArsnovaSocketioServer;
 import de.thm.arsnova.websocket.ArsnovaSocketioServerImpl;
-import de.thm.arsnova.websocket.ArsnovaSocketioServerListener;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.beans.factory.config.PropertiesFactoryBean;
@@ -275,11 +274,6 @@ public class AppConfig implements WebMvcConfigurer {
 		return socketioServer;
 	}
 
-	@Bean
-	public ArsnovaSocketioServerListener arsnovaSocketListener() {
-		return new ArsnovaSocketioServerListener();
-	}
-
 	@Bean
 	public CacheManager cacheManager() {
 		return new ConcurrentMapCacheManager();

src/main/java/de/thm/arsnova/event/ArsnovaEvent.java

@@ -30,6 +30,4 @@ public abstract class ArsnovaEvent extends ApplicationEvent {
 		super(source);
 	}
 
-	public abstract void accept(ArsnovaEventVisitor visitor);
-
 }

src/main/java/de/thm/arsnova/event/ArsnovaEventVisitor.java

-/*
- * This file is part of ARSnova Backend.
- * Copyright (C) 2012-2018 The ARSnova Team and Contributors
- *
- * ARSnova Backend is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * ARSnova Backend is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- */
-package de.thm.arsnova.event;
-
-/**
- * Listeners wanting to receive ARSnova's internal events should implement this interface.
- */
-public interface ArsnovaEventVisitor {
-
-	void visit(NewCommentEvent newCommentEvent);
-
-	void visit(DeleteCommentEvent deleteCommentEvent);
-
-	void visit(NewQuestionEvent newQuestionEvent);
-
-	void visit(UnlockQuestionEvent unlockQuestionEvent);
-
-	void visit(UnlockQuestionsEvent newQuestionsEvent);
-
-	void visit(LockQuestionEvent lockQuestionEvent);
-
-	void visit(LockQuestionsEvent lockQuestionsEvent);
-
-	void visit(NewAnswerEvent newAnswerEvent);
-
-	void visit(DeleteAnswerEvent deleteAnswerEvent);
-
-	void visit(DeleteQuestionEvent deleteQuestionEvent);
-
-	void visit(DeleteAllQuestionsEvent deleteAllQuestionsEvent);
-
-	void visit(DeleteAllQuestionsAnswersEvent deleteAllAnswersEvent);
-
-	void visit(DeleteAllPreparationAnswersEvent deleteAllPreparationAnswersEvent);
-
-	void visit(DeleteAllLectureAnswersEvent deleteAllLectureAnswersEvent);
-
-	void visit(NewFeedbackEvent newFeedbackEvent);
-
-	void visit(DeleteFeedbackForRoomsEvent deleteFeedbackEvent);
-
-	void visit(StatusRoomEvent statusSessionEvent);
-
-	void visit(ChangeScoreEvent changeLearningProgress);
-
-	void visit(PiRoundDelayedStartEvent piRoundDelayedStartEvent);
-
-	void visit(PiRoundEndEvent piRoundEndEvent);
-
-	void visit(PiRoundCancelEvent piRoundCancelEvent);
-
-	void visit(PiRoundResetEvent piRoundResetEvent);
-
-	void visit(NewRoomEvent newSessionEvent);
-
-	void visit(DeleteRoomEvent deleteSessionEvent);
-
-	void visit(LockVoteEvent lockVoteEvent);
-
-	void visit(LockVotesEvent lockVotesEvent);
-
-	void visit(UnlockVoteEvent unlockVoteEvent);
-
-	void visit(UnlockVotesEvent unlockVotesEvent);
-
-	void visit(FeatureChangeEvent featureChangeEvent);
-
-	void visit(LockFeedbackEvent lockFeedbackEvent);
-
-	void visit(FlipFlashcardsEvent flipFlashcardsEvent);
-}

src/main/java/de/thm/arsnova/event/ChangeScoreEvent.java

@@ -30,9 +30,4 @@ public class ChangeScoreEvent extends RoomEvent {
 		super(source, room);
 	}
 
-	@Override
-	public void accept(ArsnovaEventVisitor visitor) {
-		visitor.visit(this);
-	}
-
 }

src/main/java/de/thm/arsnova/event/DeleteAllLectureAnswersEvent.java

@@ -30,9 +30,4 @@ public class DeleteAllLectureAnswersEvent extends RoomEvent {
 		super(source, room);
 	}
 
-	@Override
-	public void accept(ArsnovaEventVisitor visitor) {
-		visitor.visit(this);
-	}
-
 }

src/main/java/de/thm/arsnova/event/DeleteAllPreparationAnswersEvent.java

@@ -29,9 +29,4 @@ public class DeleteAllPreparationAnswersEvent extends RoomEvent {
 	public DeleteAllPreparationAnswersEvent(Object source, Room room) {
 		super(source, room);
 	}
-
-	@Override
-	public void accept(ArsnovaEventVisitor visitor) {
-		visitor.visit(this);
-	}
 }

src/main/java/de/thm/arsnova/event/DeleteAllQuestionsAnswersEvent.java

@@ -29,9 +29,4 @@ public class DeleteAllQuestionsAnswersEvent extends RoomEvent {
 	public DeleteAllQuestionsAnswersEvent(Object source, Room room) {
 		super(source, room);
 	}
-
-	@Override
-	public void accept(ArsnovaEventVisitor visitor) {
-		visitor.visit(this);
-	}
 }

src/main/java/de/thm/arsnova/event/DeleteAllQuestionsEvent.java

@@ -31,9 +31,4 @@ public class DeleteAllQuestionsEvent extends RoomEvent {
 		super(source, room);
 	}
 
-	@Override
-	public void accept(ArsnovaEventVisitor visitor) {
-		visitor.visit(this);
-	}
-
 }

src/main/java/de/thm/arsnova/event/DeleteAnswerEvent.java

@@ -34,11 +34,6 @@ public class DeleteAnswerEvent extends RoomEvent {
 		this.content = content;
 	}
 
-	@Override
-	public void accept(ArsnovaEventVisitor visitor) {
-		visitor.visit(this);
-	}
-
 	public Content getQuestion() {
 		return content;
 	}

src/main/java/de/thm/arsnova/event/DeleteCommentEvent.java

@@ -34,11 +34,6 @@ public class DeleteCommentEvent extends RoomEvent {
 		this.comment = comment;
 	}
 
-	@Override
-	public void accept(ArsnovaEventVisitor visitor) {
-		visitor.visit(this);
-	}
-
 	public Comment getQuestion() {
 		return comment;
 	}

src/main/java/de/thm/arsnova/event/DeleteFeedbackForRoomsEvent.java

@@ -46,9 +46,4 @@ public class DeleteFeedbackForRoomsEvent extends ArsnovaEvent {
 		return userId;
 	}
 
-	@Override
-	public void accept(ArsnovaEventVisitor visitor) {
-		visitor.visit(this);
-	}
-
 }

src/main/java/de/thm/arsnova/event/DeleteQuestionEvent.java

@@ -38,9 +38,4 @@ public class DeleteQuestionEvent extends RoomEvent {
 		return this.content;
 	}
 
-	@Override
-	public void accept(ArsnovaEventVisitor visitor) {
-		visitor.visit(this);
-	}
-
 }

src/main/java/de/thm/arsnova/event/DeleteRoomEvent.java

@@ -31,9 +31,4 @@ public class DeleteRoomEvent extends RoomEvent {
 		super(source, room);
 	}
 
-	@Override
-	public void accept(ArsnovaEventVisitor visitor) {
-		visitor.visit(this);
-	}
-
 }

src/main/java/de/thm/arsnova/event/FeatureChangeEvent.java

@@ -30,9 +30,4 @@ public class FeatureChangeEvent extends RoomEvent {
 		super(source, room);
 	}
 
-	@Override
-	public void accept(ArsnovaEventVisitor visitor) {
-		visitor.visit(this);
-	}
-
 }

src/main/java/de/thm/arsnova/event/FlipFlashcardsEvent.java

@@ -29,9 +29,4 @@ public class FlipFlashcardsEvent extends RoomEvent {
 	public FlipFlashcardsEvent(Object source, Room room) {
 		super(source, room);
 	}
-
-	@Override
-	public void accept(ArsnovaEventVisitor visitor) {
-		visitor.visit(this);
-	}
 }

src/main/java/de/thm/arsnova/event/LockFeedbackEvent.java

@@ -29,9 +29,4 @@ public class LockFeedbackEvent extends RoomEvent {
 	public LockFeedbackEvent(Object source, Room room) {
 		super(source, room);
 	}
-
-	@Override
-	public void accept(ArsnovaEventVisitor visitor) {
-		visitor.visit(this);
-	}
 }

src/main/java/de/thm/arsnova/event/LockQuestionEvent.java

@@ -38,9 +38,4 @@ public class LockQuestionEvent extends RoomEvent {
 		return this.content;
 	}
 
-	@Override
-	public void accept(ArsnovaEventVisitor visitor) {
-		visitor.visit(this);
-	}
-
 }

src/main/java/de/thm/arsnova/event/LockQuestionsEvent.java

@@ -40,9 +40,4 @@ public class LockQuestionsEvent extends RoomEvent {
 		return this.contents;
 	}
 
-	@Override
-	public void accept(ArsnovaEventVisitor visitor) {
-		visitor.visit(this);
-	}
-
 }