MongoDB saving _id as a string (java)

Question

I have an object that has a parent class that may or may not set a _id field.

In this case, the _id field is not set and I pass an object through to

collection.insertOne(object)

Normally mongo generates a ObjectId() for a _id that isn't specified, but for some reason whenever _id is specified by a parent class and is not set, it is generating an id, bug is saving the id as a string in the database rather than an ObjectId.

What I'm passing through

{ "name" : "name" }

Expected:

{ "_id" : ObjectId("5cb89a7cf5e722a3d493ce8b"), "name" : "name" }

Actual:

{ "_id" : "5cb89a7cf5e722a3d493ce8b", "name" : "name" }

What I think is happening is that it sees that the parent class has a _id field, but can't find it, causing somthing like this to be passed through.

{ "_id" : null, "name" : "name" }

and as a result mongo doesn't generate an ObjectId but a string.

Is this a bug?

Thanks in advance!

There are other classes that require this to not always be an object id but as a string. — Andy
I'm trying to upgrade to mongo 4 and it is giving me this issue. Our previous version of mongo saved it as an objectId. (Mongo v3.4.14) — Andy

RomanHDev RomanHDev · Accepted Answer · 2019-04-18T16:22:08

I think this is the normal behavior of mongoDB. I only use mongo with javascript and this is the behavior it always shows. I‘m wondering if this actually makes any difference for your usecase, as the id is still unique

MongoDB saving _id as a string (java)

1 Answers