DATAMONGO-2168 - Do not map type key in QueryMapper.

QueryMapper now excludes the type key in during mapping and retains the value as-is. This change fixes an issue in which type keys were attempted to be mapped using the entity model. Type key resolution for _class failed silently while other type keys such as className failed in property path resolution and the failure became visible.

Original Pull Request: #631

Author: mp911de

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/QueryMapper.java

@@ -127,6 +127,11 @@ public Document getMappedObject(Bson query, @Nullable MongoPersistentEntity<?> e
 				continue;
 			}
 
+			if (isTypeKey(key)) {
+				result.put(key, BsonUtils.get(query, key));
+				continue;
+			}
+
 			if (isKeyword(key)) {
 				result.putAll(getMappedKeyword(new Keyword(query, key), entity));
 				continue;
@@ -629,6 +634,18 @@ protected boolean isNestedKeyword(Object candidate) {
 		return isKeyword(keys.iterator().next().toString());
 	}
 
+	/**
+	 * Returns whether the given {@link String} is the type key.
+	 * 
+	 * @param key
+	 * @return
+	 * @see MongoTypeMapper#isTypeKey(String)
+	 * @since 2.2
+	 */
+	protected boolean isTypeKey(String key) {
+		return converter.getTypeMapper().isTypeKey(key);
+	}
+
 	/**
 	 * Returns whether the given {@link String} is a MongoDB keyword. The default implementation will check against the
 	 * set of registered keywords returned by {@link #getKeywords()}.

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/convert/QueryMapperUnitTests.java

@@ -55,6 +55,7 @@
 import org.springframework.data.mongodb.core.query.BasicQuery;
 import org.springframework.data.mongodb.core.query.Criteria;
 import org.springframework.data.mongodb.core.query.Query;
+import org.springframework.data.mongodb.test.util.Assertions;
 import org.springframework.data.mongodb.test.util.BasicDbListBuilder;
 
 import com.mongodb.BasicDBObject;
@@ -803,6 +804,17 @@ public void leavesNonObjectIdStringIdRepresentationUntouchedWhenReferencingIdPro
 		assertThat(document.get("sample._id"), instanceOf(String.class));
 	}
 
+	@Test // DATAMONGO-2168
+	public void getMappedObjectShouldNotMapTypeHint() {
+
+		converter.setTypeMapper(new DefaultMongoTypeMapper("className"));
+
+		org.bson.Document update = new org.bson.Document("className", "foo");
+		org.bson.Document mappedObject = mapper.getMappedObject(update, context.getPersistentEntity(UserEntity.class));
+
+		Assertions.assertThat(mappedObject).containsEntry("className", "foo");
+	}
+
 	@Document
 	public class Foo {
 		@Id private ObjectId id;