mongodb 查詢指定字段

@Autowired
MongoDatabase database;

@Override
public List<Grid> getAdditionalGrid(String collection, int cityDataId) {
    MongoCollection<Document> gridColl = database.getCollection("grid");
        FindIterable<Document> grids = gridColl.find(Filters.eq("cityDataId", cityDataId))
                .projection(new BasicDBObject().append("grid_id", true).append("_id",true));
        }

    }