Add a 'view' parameter for all entity endpoints

A JsonView for serialization is applied based on the 'view' query
parameter.

The following values are currently supported:
* admin (View.Admin.class)
* owner (View.Owner.class)
* <unset> (Public.Admin.class)

src/main/java/de/thm/arsnova/controller/JsonViewControllerAdvice.java

+/*
+ * This file is part of ARSnova Backend.
+ * Copyright (C) 2012-2019 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.controller;
+
+import de.thm.arsnova.model.serialization.View;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.core.MethodParameter;
+import org.springframework.http.MediaType;
+import org.springframework.http.converter.json.MappingJacksonValue;
+import org.springframework.http.server.ServerHttpRequest;
+import org.springframework.http.server.ServerHttpResponse;
+import org.springframework.security.access.prepost.PreAuthorize;
+import org.springframework.web.bind.annotation.ControllerAdvice;
+import org.springframework.web.servlet.mvc.method.annotation.AbstractMappingJacksonResponseBodyAdvice;
+import org.springframework.web.util.UriComponentsBuilder;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * This {@link ControllerAdvice} applies a {@link View} based on the
+ * <code>view</code> query parameter which is used by
+ * {@link com.fasterxml.jackson.annotation.JsonView} for serialization and makes
+ * sure that the user is authorized.
+ *
+ * @author Daniel Gerhardt
+ */
+@ControllerAdvice
+public class JsonViewControllerAdvice extends AbstractMappingJacksonResponseBodyAdvice {
+	private static final String VIEW_PARAMETER = "view";
+
+	private static final Logger logger = LoggerFactory.getLogger(JsonViewControllerAdvice.class);
+
+	@Override
+	protected void beforeBodyWriteInternal(final MappingJacksonValue bodyContainer,
+			final MediaType contentType, final MethodParameter returnType,
+			final ServerHttpRequest request, final ServerHttpResponse response) {
+		/* TODO: Why does @ControllerAdvice(assignableTypes = AbstractEntityController.class) not work? */
+		if (!AbstractEntityController.class.isAssignableFrom(returnType.getContainingClass())) {
+			return;
+		}
+
+		final List<String> viewList = UriComponentsBuilder.fromUri(request.getURI()).build()
+				.getQueryParams().getOrDefault(VIEW_PARAMETER, Collections.emptyList());
+		if (viewList.isEmpty()) {
+			return;
+		}
+		final String view = viewList.get(0);
+		logger.debug("'{}' parameter found in request URI: {}", VIEW_PARAMETER, view);
+		if (bodyContainer.getValue() instanceof Collection) {
+			logger.warn("'{}' parameter is currently not supported for listing endpoints.", VIEW_PARAMETER);
+		}
+		tryAccess(bodyContainer.getValue(), view);
+		switch (view) {
+			case "owner":
+				bodyContainer.setSerializationView(View.Owner.class);
+				break;
+			case "admin":
+				bodyContainer.setSerializationView(View.Admin.class);
+				break;
+			default:
+				return;
+		}
+	}
+
+	@PreAuthorize("hasPermission(#targetDomainObject, #permission)")
+	protected void tryAccess(final Object targetDomainObject, final Object permission) {
+		/* Access check is done by aspect. No additional implementation needed. */
+	}
+}

src/main/java/de/thm/arsnova/model/serialization/View.java

@@ -18,6 +18,8 @@
 package de.thm.arsnova.model.serialization;
 
 public class View {
-	public interface Public {}
 	public interface Persistence {}
+	public interface Public {}
+	public interface Owner extends Public {}
+	public interface Admin extends Owner {}
 }