DATAMONGO-657 - Support DBRef for maps

Added capability to write DBRef instances for map values. Reading had been supported before but writing wasn't.

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

@@ -71,6 +71,7 @@ import com.mongodb.DBRef;
  * 
  * @author Oliver Gierke
  * @author Jon Brisbin
+ * @author Patrik Wasik
  */
 public class MappingMongoConverter extends AbstractMongoConverter implements ApplicationContextAware {
 
@@ -414,8 +415,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		}
 
 		if (valueType.isMap()) {
-			BasicDBObject mapDbObj = new BasicDBObject();
-			writeMapInternal((Map<Object, Object>) obj, mapDbObj, type);
+			DBObject mapDbObj = createMap((Map<Object, Object>) obj, prop);
 			dbo.put(name, mapDbObj);
 			return;
 		}
@@ -495,6 +495,42 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		return dbList;
 	}
 
+	/**
+	 * Writes the given {@link Map} using the given {@link MongoPersistentProperty} information.
+	 * 
+	 * @param map must not {@literal null}.
+	 * @param property must not be {@literal null}.
+	 * @return
+	 */
+	protected DBObject createMap(Map<Object, Object> map, MongoPersistentProperty property) {
+
+		Assert.notNull(map, "Given map must not be null!");
+		Assert.notNull(property, "PersistentProperty must not be null!");
+
+		if (!property.isDbReference()) {
+			return writeMapInternal(map, new BasicDBObject(), property.getTypeInformation());
+		}
+
+		BasicDBObject dbObject = new BasicDBObject();
+
+		for (Map.Entry<Object, Object> entry : map.entrySet()) {
+
+			Object key = entry.getKey();
+			Object value = entry.getValue();
+
+			if (conversions.isSimpleType(key.getClass())) {
+
+				String simpleKey = potentiallyEscapeMapKey(key.toString());
+				dbObject.put(simpleKey, value != null ? createDBRef(value, property.getDBRef()) : null);
+
+			} else {
+				throw new MappingException("Cannot use a complex object as a key value.");
+			}
+		}
+
+		return dbObject;
+	}
+
 	/**
 	 * Populates the given {@link BasicDBList} with values from the given {@link Collection}.
 	 * 

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

@@ -72,6 +72,7 @@ import com.mongodb.util.JSON;
  * Unit tests for {@link MappingMongoConverter}.
  * 
  * @author Oliver Gierke
+ * @author Patrik Wasik
  */
 @RunWith(MockitoJUnitRunner.class)
 public class MappingMongoConverterUnitTests {
@@ -1321,6 +1322,53 @@ public class MappingMongoConverterUnitTests {
 		converter.read(ObjectContainer.class, input);
 	}
 
+	/**
+	 * @see DATAMONGO-657
+	 */
+	@Test
+	public void convertDocumentWithMapDBRef() {
+
+		MapDBRef mapDBRef = new MapDBRef();
+
+		MapDBRefVal val = new MapDBRefVal();
+		val.id = BigInteger.ONE;
+
+		Map<String, MapDBRefVal> mapVal = new HashMap<String, MapDBRefVal>();
+		mapVal.put("test", val);
+
+		mapDBRef.map = mapVal;
+
+		BasicDBObject dbObject = new BasicDBObject();
+		converter.write(mapDBRef, dbObject);
+
+		DBObject map = (DBObject) dbObject.get("map");
+
+		assertThat(map.get("test"), instanceOf(DBRef.class));
+
+		DBObject mapValDBObject = new BasicDBObject();
+		mapValDBObject.put("_id", BigInteger.ONE);
+
+		DBRef dbRef = mock(DBRef.class);
+		when(dbRef.fetch()).thenReturn(mapValDBObject);
+
+		((DBObject) dbObject.get("map")).put("test", dbRef);
+
+		MapDBRef read = converter.read(MapDBRef.class, dbObject);
+
+		assertThat(read.map.get("test").id, is(BigInteger.ONE));
+	}
+
+	@Document
+	class MapDBRef {
+		@org.springframework.data.mongodb.core.mapping.DBRef
+		Map<String, MapDBRefVal> map;
+	}
+
+	@Document
+	class MapDBRefVal {
+		BigInteger id;
+	}
+
 	static class GenericType<T> {
 		T content;
 	}