Throw exception if class cannot get mapped because it was not scanned.

core/src/main/java/org/neo4j/ogm/session/delegates/ExecuteQueriesDelegate.java

@@ -30,6 +30,7 @@
 import org.neo4j.ogm.cypher.query.DefaultGraphModelRequest;
 import org.neo4j.ogm.cypher.query.DefaultRestModelRequest;
 import org.neo4j.ogm.cypher.query.DefaultRowModelRequest;
+import org.neo4j.ogm.exception.core.MappingException;
 import org.neo4j.ogm.metadata.ClassInfo;
 import org.neo4j.ogm.metadata.FieldInfo;
 import org.neo4j.ogm.model.GraphModel;
@@ -51,6 +52,7 @@
  * @author Vince Bickers
  * @author Luanne Misquitta
  * @author Jasper Blues
+ * @author Gerrit Meier
  */
 public class ExecuteQueriesDelegate extends SessionDelegate {
 
@@ -73,7 +75,21 @@ public <T> T queryForObject(Class<T> type, String cypher, Map<String, ?> paramet
             throw new RuntimeException("Result not of expected size. Expected 1 row but found " + resultSize);
         }
 
-        return results.iterator().next();
+        T next = results.iterator().next();
+
+        if (!next.getClass().isAssignableFrom(type)) {
+
+            String typeOfResult = next.getClass().getName();
+            String wantedType = type.getName();
+            String message = String.format(
+                "Cannot map %s to %s. This can be caused by missing registration of %s.",
+                typeOfResult, wantedType, wantedType
+            );
+
+            throw new MappingException(message);
+        }
+
+        return next;
     }
 
     public Result query(String cypher, Map<String, ?> parameters) {

test/src/test/java/org/neo4j/ogm/persistence/session/capability/QueryCapabilityTest.java

@@ -13,6 +13,7 @@
 
 package org.neo4j.ogm.persistence.session.capability;
 
+import static java.util.Collections.*;
 import static org.assertj.core.api.Assertions.*;
 
 import java.io.IOException;
@@ -30,6 +31,8 @@
 import org.neo4j.ogm.domain.cineasts.annotated.Movie;
 import org.neo4j.ogm.domain.cineasts.annotated.Rating;
 import org.neo4j.ogm.domain.cineasts.annotated.User;
+import org.neo4j.ogm.domain.restaurant.Restaurant;
+import org.neo4j.ogm.exception.core.MappingException;
 import org.neo4j.ogm.model.Result;
 import org.neo4j.ogm.response.model.NodeModel;
 import org.neo4j.ogm.session.Session;
@@ -40,6 +43,7 @@
 
 /**
  * @author Luanne Misquitta
+ * @author Gerrit Meier
  */
 public class QueryCapabilityTest extends MultiDriverTestClass {
 
@@ -710,6 +714,11 @@ public void shouldMapCypherCollectionsToArrays() {
         assertThat(((Object[]) row.get("names")).length).isEqualTo(0);
     }
 
+    @Test(expected = MappingException.class)
+    public void shouldThrowExceptionIfTypeMismatchesInQueryForObject() {
+        session.queryForObject(Restaurant.class, "MATCH (n:User) return count(n)", emptyMap());
+    }
+
     private boolean checkForMichal(Map<String, Object> result, boolean foundMichal) {
         if (result.get("n") instanceof User) {
             User u = (User) result.get("n");