playcommunity / play-mongo   0.3.1


A module for Play Framework to play with MongoDB.

Scala versions: 2.12


For the chinese introduction, refer to

What's play-mongo ?

play-mongo is a mongodb module for Play Framework, aims to introduce a concise way to play with mongodb while developing with Play Framework. It's designed based on Official Mongodb Scala Driver and bring more pragmatic features, such as:

  • A concise way for playing with mongodb
  • Auto generate the codecs of case class models
  • Auto conversion between JsValue and BsonValue
  • More convenient to deal with GridFS
  • Methods for converting change stream to akka stream.
  • Support relationship query

Getting Started

Add the following dependency to your build.sbt,

libraryDependencies += "cn.playscala" % "play-mongo_2.12" % "0.3.0"

addCompilerPlugin("org.scalamacros" % "paradise" % "2.1.1" cross CrossVersion.full)

And append your mongodb connection config to conf/application.conf,

mongodb.uri = "mongodb://user:password@host:port/dbName?authMode=scram-sha1"

Then before the application starts, config where to find your models, modify app/Module class as follows,

class Module extends AbstractModule {
  override def configure() = {

Mongo.setModelsPackage method will find all case classes in models package, auto-generating the related codecs, and add these codes to the driver. After all, you can inject Mongo instance into where you want.

class Application @Inject()(cc: ControllerComponents, mongo: Mongo) extends AbstractController(cc) {}

Auto-generate Json Formats for case classes

Thanks to Json.format macro, we can generate the implicit Reads and Writes of case class as follows,

import models._
import play.api.libs.json.Format
package object models {
  implicit val emailFormat = Json.format[Email]
  implicit val personFormat = Json.format[Person]
  implicit val addressFormat = Json.format[Address]

But every time we create a new case class, we have to create a implicit Format here. So we implement a macro annotation @JsonFormat, which can auto-generate implicit json formats for case classes,

import cn.playscala.mongo.codecs.macrocodecs.JsonFormat
package object models {
  implicit val formats = ???

@JsonFormat macro annotation receive a package name as a parameter, which designates the package name of models.

Model and Collection

A model class represent a document of the mongodb's collection (a collection is just like the table in relation database), which is a case class annotated with @Entity annotation,

case class User(_id: String, name: String, password: String, addTime: Instant)

The parameter value of @Entity specify the collection name in mongodb, if not specified, default to the class name. As a convention, _id is used as the identity field of model classes, which is the same as the primary key in the related collection of mongodb.

There are two ways to access the mongodb's collection, the first way is using the model class,

mongo.find[User]().list().map{ users => ... }

The parameter type User here not only specify the related mongodb's collection, but also specify the result type. That means the query will be sent to common-user collection, and the result type of query is User. Notice that, the result type in this way can't be changed. The second way is using mongo.getCollection method,

mongo.collection("common-user").find[User]().list().map{ users => }

Here, the parameter type User in find method only specify the result type of query, we can change this parameter type to change the result type,

mongo.collection("common-user").find[JsObject]().list().map{ jsObjList => }
mongo.collection("common-user").find[CommonUser](Json.obj("userType" -> "common")).list().map{ commonUsers => }

You can also use model class to specify the related mongodb's collection,

mongo.collection[User].find[User]().list().map{ user => }

The first parameter type User specifies the related mongodb's collection, and the second parameter type User specifies the result type. You can change the second parameter type 'User' to change the result type.

Common Operations

The following codes are supposed to have import play.api.libs.json.Json._ in current scope. So you can write obj() instead of Json.obj().


// Insert Model
mongo.insert[User](User("0", "joymufeng", "123456",

// Insert Json
val jsObj = obj("_id" -> "0", "name" -> "joymufeng", "password" -> "123456", "addTime" ->


mongo.updateById[User]("0", obj("$set" -> obj("password" -> "123321")))
mongo.updateOne[User](obj("_id" -> "0"), obj("$set" -> obj("password" -> "123321")))

mongo.collection[User].updateById("0", obj("$set" -> obj("password" -> "123321")))
mongo.collection[User].updateOne(obj("_id" -> "0"), obj("$set" -> obj("password" -> "123321")))

mongo.collection("common-user").updateById("0", obj("$set" -> obj("password" -> "123321")))
mongo.collection("common-user").updateOne(obj("_id" -> "0"), obj("$set" -> obj("password" -> "123321")))


mongo.findById[User]("0") // Future[Option[User]]
mongo.find[User](obj("_id" -> "0")).first // Future[Option[User]]

mongo.collection[User].findById[User]("0") // Future[Option[User]]
mongo.collection[User].find[User](obj("_id" -> "0")).first // Future[Option[User]]

mongo.collection[User].findById[JsObject]("0") // Future[Option[JsObject]]
mongo.collection[User].find[JsObject](obj("_id" -> "0")).first // Future[Option[JsObject]]

mongo.collection("common-user").findById[User]("0") // Future[Option[User]]
mongo.collection("common-user").find[User](obj("_id" -> "0")).first // Future[Option[User]]

mongo.collection("common-user").findById[JsObject]("0") // Future[Option[JsObject]]
mongo.collection("common-user").find[JsObject](obj("_id" -> "0")).first // Future[Option[JsObject]]


mongo.deleteOne[User](obj("_id" -> "0"))

mongo.collection[User].deleteOne(obj("_id" -> "0"))

mongo.collection("common-user").deleteOne(obj("_id" -> "0"))

Upload and Download Files

// Upload and get the fileId
mongo.gridFSBucket.uploadFromFile("kf.jpg", "image/jpg", new File("./kf.jpg")).map{ fileId =>

// Download file by fileId
  case Some(file) =>
  case None =>

Change Stream

toSource method will transform Change Stream to Akka Source, and then things become more funny. For example, we can achieve the following features with several line of codes,

  • Buffer the elements of Change Stream for bulk processes, and pass to next step if either of the two conditions is established
    • up to 10 elements
    • exceed to 1000 ms
  • Traffic shaping with 1 passed per second
  .groupedWithin(10, 1000.millis)
  .throttle(elements = 1, per = 1.second, maximumBurst = 1, ThrottleMode.shaping)
  .runForeach{ seq => 
    // ...

Relationship Query

case class Article(_id: String, title: String, content: String, authorId: String)

case class Author(_id: String, name: String)

mongo.find[Article].fetch[Author]("authorId").list().map{{ t =>
    val (article, author) = t

For each article, the related author will be fetched on condition article.authorId == author._id.

Class, Json and Bson

You should be more careful while working with json, because JsNumber is used to represent all numeric values in json. On the other side, Bson has more concrete numeric types. That means the conversion between Json and Bson is irreversible due to the asymmetry numeric types. Next step, we will analyze some common scenes. The following is the model class which will be used.

case class User(_id: String, name: String, setting: UserSetting)
case class UserSetting(gender: String, age: Int)

Class -> Bson

We usually insert a model class instance into mongodb like this,

mongo.insert[User].insert(User("0", "joymufeng", UserSetting("male", 32)))

Before invoking the underlying driver,User will be converted to Bson, and this conversion is reversible. While read from mongodb, the Bson document could be converted to User successfully.

Json -> Bson

While we construct a JsObject using Json DSL, all numeric values(such as Byte, Short, Int, Long, Float and Double) will be converted to JsNumber(with BigDecimal inside), the concrete types of numeric values lost in this conversion. Before invoking the underlying driver,Json will be converted to Bson, and JsNumber will be converted to BsonDecimal128. While read from mongodb, we can't recover the concrete types of the original numeric values. For example, we usually writes the following update operations,

mongo.updateById[User]("0", obj("$set" -> UserSetting("male", 18)))
// Or
mongo.updateById[User]("0", obj("$set" -> obj("setting" -> obj("gender" -> "male", "age" -> 18))))

Both UserSetting("male", 32) and obj("gender" -> "male", "age" -> 18) will be converted to obj("gender" -> JsString("male"), "age" -> JsNumber(BigDecimal(18)). So after these update operations, the type of user.setting.age field in mongodb will be NumberDecimal, while read it back, an error occurs,

// [BsonInvalidOperationException: Invalid numeric type, found: DECIMAL128]

While try to convert BigDecimal to Int, an exception is thrown. Because the precision value will be lost in this conversion. To solve this problem, we will convert JsNumber to a narrow type as much as possible, so it could be safely read back. For example, obj("age" -> JsNumber(18.0)) will be converted to BsonDocument("age", BsonInt32(18)).