Mongo4cats

Mongo4cats is a Scala library that provides a functional and idiomatic interface for working with MongoDB. It is built on top of the official MongoDB Java driver and has a dedicated ZIO 2 module.

Introduction

Mongo4cats integrates with both Cats Effect/FS2 and ZIO. The ZIO module exposes the client, database, and collection as ZIO services (ZMongoClient, ZMongoDatabase, and ZMongoCollection), with a fluent API for building filters, projections, and sorting. It is available for Scala 2.12, 2.13, and 3.

Installation

In order to use this library with ZIO 2, we need to add the following lines to our build.sbt file:

libraryDependencies += "io.github.kirill5k" %% "mongo4cats-zio" % "0.8.0"
libraryDependencies += "io.github.kirill5k" %% "mongo4cats-zio-embedded" % "0.8.0" % Test

The mongo4cats-zio-embedded module is optional and provides an embedded MongoDB for tests. To encode and decode documents with ZIO JSON, also add:

libraryDependencies += "io.github.kirill5k" %% "mongo4cats-zio-json" % "0.8.0"

Example

The following example connects to a local MongoDB, inserts some documents, and queries them:

import mongo4cats.bson.Document
import mongo4cats.bson.syntax._
import mongo4cats.operations.{Filter, Projection}
import mongo4cats.zio.{ZMongoClient, ZMongoCollection, ZMongoDatabase}
import zio._

object Zio extends ZIOAppDefault {

  val client     = ZLayer.scoped[Any](ZMongoClient.fromConnectionString("mongodb://localhost:27017"))
  val database   = ZLayer.fromZIO(ZIO.serviceWithZIO[ZMongoClient](_.getDatabase("my-db")))
  val collection = ZLayer.fromZIO(ZIO.serviceWithZIO[ZMongoDatabase](_.getCollection("docs")))

  val program = for {
    coll <- ZIO.service[ZMongoCollection[Document]]
    _    <- coll.insertMany((0 to 100).map(i => Document("name" := s"doc-$i", "index" := i)))
    docs <- coll.find
      .filter(Filter.gte("index", 10) && Filter.regex("name", "doc-[1-9]0"))
      .projection(Projection.excludeId)
      .sortByDesc("name")
      .limit(5)
      .all
    _ <- Console.printLine(docs.mkString("[\n", ",\n", "\n]"))
  } yield ()

  override def run = program.provide(client, database, collection)
}

For the full documentation, see the Mongo4cats microsite.