Return proper error code, embed message in error template

See #414

app/controllers/Application.java

@@ -354,9 +354,13 @@ location, from, size, responseFormat, lang().code(),
 			Logger.debug("Caching search result for request: {}", cacheKey);
 			Cache.set(cacheKey, searchResult, ONE_DAY);
 			return searchResult;
-		} catch (IllegalArgumentException x) {
-			Logger.warn("Bad request: ", x.getMessage());
-			return badRequest("Bad request: " + x.getMessage());
+		} catch (Throwable t) {
+			String message = t.getMessage()
+					+ (t.getCause() != null ? ", cause: " + t.getCause().getMessage()
+							: "");
+			Logger.error("Error: {}", message);
+			return internalServerError(
+					views.html.error.render(q, "Error: " + message));
 		}
 	}
 
@@ -614,9 +618,6 @@ static String[] defaultAggregations() {
 	}
 
 	private static String returnAsJson(SearchResponse queryResponse) {
-		if (queryResponse == null) {
-			return Json.newObject().toString();
-		}
 		List<Map<String, Object>> hits =
 				Arrays.asList(queryResponse.getHits().hits()).stream()
 						.map(hit -> hit.getSource()).collect(Collectors.toList());

app/controllers/Index.java

@@ -149,14 +149,7 @@ static SearchResponse executeQuery(int from, int size, QueryBuilder query,
 		if (!aggregations.isEmpty()) {
 			searchRequest = withAggregations(searchRequest, aggregations.split(","));
 		}
-		try {
-			return searchRequest.execute().actionGet();
-		} catch (Throwable t) {
-			Logger.error("Could not execute request: {}, cause: {}", t.getMessage(),
-					t.getCause().getMessage());
-			Logger.debug("Could not execute request", t);
-			return null;
-		}
+		return searchRequest.execute().actionGet();
 	}
 
 	private static QueryBuilder preprocess(QueryBuilder query) {

app/views/error.scala.html

@@ -0,0 +1,12 @@
+@* Copyright 2018 Fabian Steeg, hbz. Licensed under the GPLv2 *@
+
+@(q: String, message: String)
+
+@import play.i18n._
+
+@main(q) { 
+	<div class="panel panel-danger footer">
+		<div class='panel-heading'>@Messages.get("error")</div>
+		<div class='panel-body'>@message</div>
+	</div>
+}

conf/messages.de

@@ -150,3 +150,5 @@ dataset.distribution.documentation = Dokumentation
 dataset.distribution.url = URL
 dataset.distribution.license = Lizenz
 dataset.distribution.media = Medientypen
+
+error = Fehler

conf/messages.en

@@ -150,3 +150,5 @@ dataset.distribution.documentation = Documentation
 dataset.distribution.url = URL
 dataset.distribution.license = License
 dataset.distribution.media = Media types
+
+error = Error