从mongodb结果java中删除_id

Question

我的代码是

  DBCollection collection = db.getCollection("volume");
  DBCursor cursor = collection.find();
  DBObject resultElement = cursor.next();
  Map resultElementMap = resultElement.toMap();
  System.out.println(resultElementMap);

结果是:

{_id = 521b509d20954a0aff8d9b02,title = {"text":"工作量订单","x": - 20.0},xAxis = {"title":{"text":"2012"},"categories":[" Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"]},yAxis = {"min":1000.0,"max":7000.0,"title":{"text":"Volume(K)"},"plotLines":[{"label":{"text":"Average", "x":25.0},"color":"black","width":2.0,"value":30.0,"dashStyle":"solid"}]},legend = {"backgroundColor":"#FFFFFF", "reversed":true},series = [{"name":"Volume","showInLegend":false,"data":[2909.0,3080.0,4851.0,3087.0,2960.0,2911.0,1900.0,3066.0,3029.0,5207.0, 3056.0,3057.0]}]}

我需要从结果中删除_id.我知道我需要和collection.find()一起玩,但请有人帮助我吗？我无法获得结果

Answer 1

两种选择:

您可以从创建的地图中删除"_id"字段:

...
resultElementMap.remove("_id");
System.out.println(resultElementMap);

或者您可以要求查询结果不包含_id字段:

DBObject allQuery = new BasicDBObject();
DBObject removeIdProjection = new basicDBObject("_id", 0);

DBCollection collection = db.getCollection("volume");
DBCursor cursor = collection.find(allQuery, removeIdProjection);
DBObject resultElement = cursor.next();
Map resultElementMap = resultElement.toMap();
System.out.println(resultElementMap);

有关所有详细信息,请参阅有关投影的文档.