mongodb - Mongo java驱动中，有没有封装好的函数，可以直接取到文档中的某个具体的值，而不是一个文档？或者有没有方法实现？？

Question

{"_id":"37389873",
"Date":{
"name":{"count":"7",
"user": "liyang",
}

     }

}

比如数据库中存的这个文档，我想取count中的值7，只取数字7，不要文档，改怎么实现呢？？

Answer 1

Finally, I used Jackson to convert the json string into a map, and then used map to slice it layer by layer, and finally returned a numerical value

Answer 2

db.xxx.findOne({"_id":"37389873"}, {"Date.name.count": 1}).Date.name.count

Operation effect

~/tmp
▶ cat mmm.js
#!/usr/bin/env mongo

var db = connect('test');
db.xxx.drop();
db.xxx.insert({
  "_id": "37389873",
  "Date":{
         "name":{"count":"7",
                 "user": "liyang",
                 }

         }

 });

print( db.xxx.findOne({"_id":"37389873"}, {"Date.name.count": 1}).Date.name.count );


~/tmp
▶ ./mmm.js
MongoDB shell version: 2.6.3
connecting to: test
connecting to: test
7

Answer 3

http://jongo.org/
Maybe this is what you are looking for

Answer 4

spring’s mongodb plug-in can satisfy

BasicQuery query = new BasicQuery(query,fields);

query is the query condition
fields is the field to be queried

Answer 5

collections.find(docQuery).projection(keys)