Mongo JSON document -> JSON -> BSON

Question

I am working with Node.js to build a web socket server that uses mongodb.

I am using node-mongodb-native as the library to access mongo db.

When I call console.log(sys.inspect(item)) on an object from the db I get something that looks like this:

{ _id: { id: 'L?#&\u008e\u00ad\u000e\u008f\u0014\u0005\u0000\u0000' }
, y: 3
, favorite_color: 'orange'
, x: 14766
}

so I am guessing the id is the BSON object id that mongo uses.

I need to send this object to the client web browser using JSON, have them do some stuff to it, and then send it back to the server.

When I JSON.stringify(item), I get something that looks like this:

{"_id":"4c3f23268ead0e8f14050000","y":3,"favorite_color":"orange","x":14766}

So the id has been turned into some hex encoded string. If I send it to the client, and the client sends it back, I now need to update it in the db. I run JSON.parse(item) to get it to be a normal object, but it still looks like this:

{ _id: '4c3f23268ead0e8f14050000'
, y: 3
, favorite_color: 'orange'
, x: 14766
}

and that _id can't be used to look up in mongodb.

How can I convert it back to a format that will be able to be used for lookups on mongo?

--update--

Interestingly I can use findOne({_id:item._id}, collection) to get the document, but if I do this:

findOne({_id:{id : item._id.id}}, collection)

I don't receive a result. I guess there is something special about the mongo _id object.

Both {_id:item._id} and {_id:{id : item._id.id}} when dumped out look like this:

{ _id: { id: 'L?#&\u008e\u00ad\u000e\u008f\u0014\u0005\u0000\u0000' } }

--Another update RESOLVED---

There was some object id manipulation in an integration test file.

objectId = new mongo.ObjectID.createFromHexString('47cc67093475061e3d95369d'); will give the _id that I am looking for.

objectId.toHexString() will return the hex string that looks like '47cc67093475061e3d95369d'

Answer 1

Well, I was stuck with the same error while working with python client. But I will clarify the accomplishment result for both languages.

Firstly the _id MongoDB returns is the BSON object. Meaning bin­ary-en­coded seri­al­iz­a­tionfor of JSON, more in this link: BSON

Let's say you want to insert data with the following fields:

params = {
   "y":3,
   "favorite_color":"orange",
   "x":14766
}

client.connect(url, function(err, db) {
  var dbo = db.db("test_database");
dbo.collection("my_collection").insertOne(params, function(err, res) {
 if (err) throw err;
   console.log("inserted document",JSON.stringify(res));
    db.close();
   });
});

it return object result, for instance "_id":"5e95abf57b59b448bb22dedf"

Defining ObjectId, you can easily use findOne, updateOne methods.

const {ObjectId} = require('mongodb');
client.connect(url, function(err, db) {
  var dbo = db.db("test_database");
 var myquery = { "_id": ObjectId("5e95abf57b59b448bb22dedf") } ;

    dbo.collection("my_collection").findOne(myquery, function(err, result) {
      if (err) throw err;
      console.log(result);
   });

});

update:

client.connect(url, function(err, db) {
  var dbo = db.db("test_database");
   var myquery = { "_id": ObjectId("5e95abf57b59b448bb22dedf") } ;
    var newvalues = { $set: {favorite_color: "red", y: "14760" } };
    dbo.collection("my_collection").updateOne(myquery, newvalues, function(err, res) {
      if (err) throw err;
      console.log("1 document updated");
      db.close();
    });
});

For python:

let's take this result as an example: {'_id':ObjectId('5e95a18dcae4a4a005e14bd8')}

from bson.json_util import loads as bson_loads, dumps as bson_dumps 
import json


#you should dump it then load it 
result = document = json.loads(bson_dumps(document))
{ "$set": {"status": False}}

#update:
db["my_collection"].update_one({ "_id": result},new_value)  

#find_one:
db["my_collection"].find_one({ "_id": resultjs})

For more to work with python MongoDB client(motor) I have created Gist

Answer 2

My guess is that sys.inspect interprets an ObjectId as an object containing an id property. That's what you're seeing in the dump.

MongoDB treats the ObjectId as a 12-byte binary value, not as an object. So MongoDB doesn't know about any id property. That's why the following query yields no result:

findOne({_id: {id: item._id.id}}, collection)

The following does work, as it just treats both values as binary values:

findOne({_id: item._id}, collection)