MongoDB Salat plugin for Play Framework 2

Salat is a ORM for MongoDBs scala driver called Casbah.

The plugin's functionality simpifies the use of salat by presenting a simple "play style" configuration and binders for ObjectId

• https://github.com/mongodb/casbah
• https://github.com/salat/salat

Installation

Start by adding the plugin, in your build.sbt

libraryDependencies += "ru.tochkak" % "play-plugins-salat" % "1.7.2"

Then we can add the implicit converstions to and from ObjectId by adding to the routesImport and add ObjectId to all the templates

We continue to edit the conf/application.conf file. We need to disable some plugins that we don't need. Add these lines:

dbplugin = disabled
evolutionplugin = disabled
ehcacheplugin = disabled

Add the following line to the conf/application.conf file. This will enable the Play-Salat module and Guice will inject it.

play.modules.enabled  += "ru.tochkak.plugin.salat.PlaySalatModule"

Configuration

now we need to setup our connections. The plugin is modeled after how plays DB plugin is built.

mongodb.default.db = "mydb"
# Optional values
#mongodb.default.host = "127.0.0.1"
#mongodb.default.port = 27017
#mongodb.default.user = "leon"
#mongodb.default.password = "123456"

# MongoURI
# ~~~~~
# a MongoURI can also be used http://www.mongodb.org/display/DOCS/Connections
# mongodb.default.uri = "mongodb://127.0.0.1:27017,mongodb.org:1337/salat-test"

# WriteConcern
# ~~~~~
# Can be any of the following
#
# fsyncsafe - Exceptions are raised for network issues and server errors; Write operations wait for the server to flush data to disk.
# replicassafe - Exceptions are raised for network issues and server errors; waits for at least 2 servers for the write operation.
# safe - Exceptions are raised for network issues and server errors; waits on a server for the write operation.
# normal - Exceptions are raised for network issues but not server errors.

#mongodb.default.writeconcern = "safe"

# Replica sets
# ~~~~~
# http://www.mongodb.org/display/DOCS/Why+Replica+Sets
#
# To user a replicaset instead of a single host, omit optional values and use the configuration below instead.
# Since replica sets use public key authentication, user and password won't work together with the replicaset option.

#mongodb.default.replicaset {
#    host1.host = "10.0.0.1"
#
#    host2.host = "10.0.0.2"
#    host2.port = 27018
#}

# Mongo Options
# ~~~~~
# http://api.mongodb.org/java/2.8.0/com/mongodb/MongoOptions.html
#
# For passing custom options to the MongoConnection add the properties under "options". Add just the ones which are different from defaults.

#mongodb.default.options {
#    connectionsPerHost = 100
#    threadsAllowedToBlockForConnectionMultiplier = 1000
#    connectTimeout = 60000
#}

More that one DB?

If you would like to connect to two databases you need to create two source names. You also can specify different options per database

mongodb.myotherdb.db = "otherdb"
mongodb.myotherdb.options.connectionsPerHost = 80

Then you can call playSalat.collection("collectionname", "myotherdb")

What a model looks like

All models must be case classes otherwise salat doesn't know how to properly transform them into MongoDBObject's

package models

import java.util.Date
import com.novus.salat.annotations._
import play.api.libs.json._
import play.api.libs.functional.syntax._
import se.radley.plugin.salat.Binders._

case class User(
  id: ObjectId = new ObjectId,
  username: String,
  password: String,
  address: List[Address] = Nil,
  added: Date = new Date(),
  updated: Option[Date] = None,
  @Key("company_id") company: Option[ObjectId] = None)

Dependency Injection

Modules managed by the Guice dependency injection framework are declared like this:

import com.google.inject.AbstractModule
import services.{ UserDAO, MongoContext }

class Module extends AbstractModule {

  override def configure() = {
    bind(classOf[MongoContext])
    bind(classOf[UserDAO])
  }
}

Collections

A Salat Mongo Context is typically implemented like this:

package services

import javax.inject._
import com.novus.salat.{ TypeHintFrequency, StringTypeHintStrategy, Context }
import play.api.Environment

@Singleton
class MongoContext @Inject() (environment: Environment) {

  implicit val context = {
    val context = new Context {
      val name = "global"
      override val typeHintStrategy = StringTypeHintStrategy(when = TypeHintFrequency.WhenNecessary, typeHint = "_t")
    }
    context.registerGlobalKeyOverride(remapThis = "id", toThisInstead = "_id")
    context.registerClassLoader(environment.classLoader)
    context
  }
}

A DAO to a collection with Salat Mongo Context and Play Salat Plugin injected is implemented like this:

package services

import javax.inject._
import com.novus.salat.dao._
import com.mongodb.casbah.Imports._
import se.radley.plugin.salat.PlaySalat
import models.User

@Singleton
class UserDAO @Inject() (playSalat: PlaySalat, mongoContext: MongoContext) extends ModelCompanion[User, ObjectId] {
  import mongoContext._

  def collection = playSalat.collection("users")
  val dao = new SalatDAO[User, ObjectId](collection) {}

  // Queries
  def findOneByUsername(username: String): Option[User] =
    dao.findOne(MongoDBObject("username" -> username))

  def findByCountry(country: String) =
    dao.find(MongoDBObject("address.country" -> country))
}

Capped Collections

If you want to use capped collections check this out.

Model:

package models

import java.util.Date
import com.mongodb.casbah.Imports._

case class LogItem(
  id: ObjectId = new ObjectId,
  message: String)

DAO (also remember to register it in the Module class):

package services

import javax.inject._
import com.novus.salat.dao._
import com.mongodb.casbah.Imports._
import se.radley.plugin.salat.PlaySalat
import models.LogItem

@Singleton
class LogItemDAO @Inject() (playSalat: PlaySalat, mongoContext: MongoContext) extends ModelCompanion[LogItem, ObjectId] {
  import mongoContext._

  val collection = playSalat.cappedCollection("logitems",
    1048576, // max size is 1 MB = 10485760 bytes
    Some(10)) // max number of documents = 10
  val dao = new SalatDAO[LogItem, ObjectId](collection) {}
}

GridFS

TODO adjust the example to use dependency injection.

If you want to store things in gridfs you can do this

package models

import play.api.Play.current
import se.radley.plugin.salat._
import mongoContext._

val files = gridFS("myfiles")

Mongo Context

All models must contain an implicit salat Context. The context is somewhat like a hibernate dialect. You can override mapping names and configure how salat does it's type hinting. read more about it here

In the sample there is a custom mongoContext, partly because we need to add plays classloader to salat so it knows when to reload it's graters, but also so we can override all models id fields to be serialized to MongoDB's _id.

• Sample