DATAMONGO-508 - Eagerly return DBRef creation if the given value already is a DBRef.

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

@@ -671,6 +671,10 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 
 		Assert.notNull(target);
 
+		if (target instanceof DBRef) {
+			return (DBRef) target;
+		}
+
 		MongoPersistentEntity<?> targetEntity = mappingContext.getPersistentEntity(target.getClass());
 
 		if (null == targetEntity) {

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

@@ -1278,6 +1278,20 @@ public class MappingMongoConverterUnitTests {
 		fail(String.format("Didn't find synthetic field on %s!", target));
 	}
 
+	/**
+	 * @see DATAMGONGO-508
+	 */
+	@Test
+	public void eagerlyReturnsDBRefObjectIfTargetAlreadyIsOne() {
+
+		DB db = mock(DB.class);
+		DBRef dbRef = new DBRef(db, "collection", "id");
+
+		org.springframework.data.mongodb.core.mapping.DBRef annotation = mock(org.springframework.data.mongodb.core.mapping.DBRef.class);
+
+		assertThat(converter.createDBRef(dbRef, annotation), is(dbRef));
+	}
+
 	static class GenericType<T> {
 		T content;
 	}