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NoSQL|Mongo : How to use ObjectID ? [message #1411128]

Fri, 22 August 2014 13:10

Tugdual Grall

Messages: 1
Registered: July 2009

Junior Member

I am not sure to understand correctly the way the ID is generated by EclipseLink.

The default BSON type - stored by MongoDB- for is an ObjectID that is automatically generated by the Java driver and store as a 12bytes in the db.

When I ask my entity to generate the ID for example

 @Id 
 @GeneratedValue()
 @Field(name="_id")
 private String id;

It looks like EclipseLink is using the ID generated by MongoDB Driver but does not store it with the correct format. It is store as a simple string.

For example, with these annotation in the shell, the id looks like:

{ "_id" : "53F740283004D7B7A21DB58E", ...

When generated properly, in the shell it should look like:

{ "_id" : ObjectId("53f73a66300403c9041fda83"), ...

Do I have any way to generate the proper Object ID for MongoDB? (I understand that you can use anything, but I would like to have my Eclipselink application to behave the same way than other FWK)

Also when I have an existing database with some document generate by another application with the proper format, I have no idea how to query -in JQL- it by ID. (since the ID is not a string but an ObjectID). For example in the shell I would use:

db.order.find( { "_id" : ObjectId("53f73a66300403c9041fda83") }  );

So, globally my question is how do we work with ObjectId in EclipseLink?

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Re: NoSQL|Mongo : How to use ObjectID ? [message #1709813 is a reply to message #1411128]

Thu, 01 October 2015 10:27

Ray Hulha

Messages: 1
Registered: October 2015

Junior Member

I recently picked up EclipseLink NoSQL plugin development and I used the MongoDB implementation to learn the basics.

So here is the way it generates the ID:

public class OIDSequence extends Sequence {

@Override
public Object getGeneratedValue(Accessor accessor, AbstractSession writeSession, String seqName) {
return new ObjectId().toByteArray();
}

...

}

If this is still important I could try to remove the toByteArray() call and see what happens.

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