Add bean validation for entity classes

Validation is performed before entities are persisted using Hibernate Validator, the reference implementation for Bean Validation 2.0 (JSR 380).

Refs #23.

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

@@ -39,6 +39,7 @@ import org.springframework.web.bind.annotation.ResponseStatus;
 import org.springframework.web.context.request.WebRequest;
 import org.springframework.web.servlet.mvc.method.annotation.ResponseEntityExceptionHandler;
 
+import de.thm.arsnova.model.EntityValidationException;
 import de.thm.arsnova.web.exceptions.BadRequestException;
 import de.thm.arsnova.web.exceptions.ForbiddenException;
 import de.thm.arsnova.web.exceptions.NoContentException;
@@ -120,6 +121,14 @@ public class ControllerExceptionHandler extends ResponseEntityExceptionHandler {
 		return helper.handleException(e, Level.DEBUG);
 	}
 
+	@ExceptionHandler(EntityValidationException.class)
+	@ResponseBody
+	@ResponseStatus(HttpStatus.BAD_REQUEST)
+	public Map<String, Object> handleEntityValidationException(
+			final EntityValidationException e, final HttpServletRequest request) {
+		return helper.handleException(e, Level.DEBUG);
+	}
+
 	@ExceptionHandler(PreconditionFailedException.class)
 	@ResponseBody
 	@ResponseStatus(HttpStatus.PRECONDITION_FAILED)