MongoDB to have auto incrementing Integer Id within a collection using Spring Data Mongo

Question

I had in an domain object @Id private Long id;

Caused by: org.springframework.dao.InvalidDataAccessApiUsageException: Cannot autogenerate id of type java.lang.Long for entity of type ...

That can be fixed with using String as @Id private String id;

But if I don't have multi threading (or take proper care of it), neither distributed MongoDB cluster, and I do really want and Id to be more friendly,
how to make integer auto incrementing MongoDB Id in Java using Spring Data MongoDB?

Versions used:

MongoDB 3.2
java mongodb-driver 3.2.2
spring-data-mongodb 1.9.2.RELEASE

import org.springframework.data.annotation.Id;

public @lombok.Data class Item {
    @Id private String id;  
    private String name;

}

alexbt · Answer 1 · 2016-09-04T02:54:36.267

MongoDB suggests 2 ways to handle that scenario: auto-increment-optimistic-loop

Use Counters Collection

Create a document to hold your sequence number

db.counters.insert(
   {
      _id: "mySequenceName",
      seq: 0
   }
)

Create a getNextSequenceNumber javascript function in mongodb

function getNextSequence() {
   var ret = db.counters.findAndModify(
          {
            query: { _id: mySequenceName },
            update: { $inc: { seq: 1 } },
            new: true
          }
   );

   return ret.seq;
}

Before inserting your document, get the nextSequence number:

BasicDBObject basicDbObject = new BasicDBObject();
basicDbObject.append( "$eval" , "getNextSequence()" );

CommandResult result = mongoTemplate.executeCommand(basicDbObject);
Object seqno = result.get("seq");

Insert your document:

Mode model...
model.setId(Long.parseLong(seqno));
repository.save(model);

Optimistic Loop

Create a custom insertDocument mongodb function

The other approach requires that you bypass spring-data for the insertion. It's all done in a mongodb javascript function (that you need to create).

The function will first retrieve the largest _id for the document your are inserting:

var cursor = targetCollection.find( {}, { _id: 1 } ).sort( { _id: -1 } ).limit(1);function insertDocument(doc, targetCollection) {

var seq = cursor.hasNext() ? cursor.next()._id + 1 : 1;

Then, you can insert the document using the sequence number:

var results = targetCollection.insert(doc);

However, because the sequence number might have been used by another simultaneous insertion, you need to check for an error, and repeat the process if needed, which is why the whole function runs in a while(1) loop.

The complete function:

function insertDocument(doc, targetCollection) {
    while (1) {

        var cursor = targetCollection.find( {}, { _id: 1 } ).sort( { _id: -1 } ).limit(1);

        var seq = cursor.hasNext() ? cursor.next()._id + 1 : 1;

        doc._id = seq;

        var results = targetCollection.insert(doc);

        if( results.hasWriteError() ) {
            if( results.writeError.code == 11000 /* dup key */ )
                continue;
            else
                print( "unexpected error inserting data: " + tojson( results ) );
        }

        break;
    }
}

Call the insertDocument mongodb function

Now, from java you would call the javascript function insertDocument. To call the mongo stored proc with a parameter, I believe doEval may be of use:

MongoClient mongoClient = new MongoClient();
DB db = mongoClient.getDB("dbName");
Model m = new Model(...);
CommandResult result = db.doEval("insertDocument", model);

MongoDB to have auto incrementing Integer Id within a collection using Spring Data Mongo

1 Answers1