A Lift helper class to generate sequential long values when using MongoDB with Record.

MongoSequence.scala

package code.model

import net.liftweb.mongodb.BsonDSL._
import net.liftweb.record.field._
import net.liftweb.util.Helpers._
import net.liftweb.common._
import net.liftweb.mongodb.record._
import field._
import com.mongodb.{DBObject, BasicDBObject}

class MongoSequence extends MongoRecord[MongoSequence] with ObjectIdPk[MongoSequence] with Loggable {
  def meta = MongoSequence

  object name extends StringField(this, 100)

  object value extends LongField(this)

}

object MongoSequence extends MongoSequence with MongoMetaRecord[MongoSequence] {
  // unique index
  ensureIndex(("name" -> 1), ("unique" -> true))

  def getNextValue(which: String): Long = {
    useColl {
      coll =>
        val finder: DBObject = new BasicDBObject("name", which)
        val upd: DBObject = new BasicDBObject("$inc", new BasicDBObject("value", 1))
        val res = coll.findAndModify(finder, null, null, false, upd, true, true)
        if (res.containsField("value"))
          asLong(res.get("value")).getOrElse(1L)
        else
          1L
    }
  }
}