Choose a Connection Target

Overview

In this guide, you can learn how to use a connection string and a MongoClient object to connect to different types of MongoDB deployments.

Atlas

To connect to a MongoDB deployment on Atlas, include the following elements in your connection string:

• The URL of your Atlas cluster

• Your MongoDB username

• Your MongoDB password

Then, pass your connection string to the MongoClient constructor.

When you connect to Atlas, we recommend using the Stable API client option to avoid breaking changes when Atlas upgrades to a new version of MongoDB Server. To learn more about the Stable API feature, see the Stable API guide.

The following code shows how to use the Kotlin Sync driver to connect to an Atlas cluster. The code also uses the serverApi() method to specify a Stable API version.

// Defines Stable API version
val serverApi = ServerApi.builder()
    .version(ServerApiVersion.V1)
    .build()
// Uses MongoClientSettings to apply connection string and specify the Stable API version
val settings = MongoClientSettings.builder()
    .applyConnectionString("<connection string URI>")
    .serverApi(serverApi)
    .build()
val mongoClient = MongoClient.create(settings)

Local Deployments

To connect to a local MongoDB deployment, use localhost as the hostname. By default, the mongod process runs on port 27017, though you can customize this for your deployment.

The following code shows how to use the Kotlin Sync driver to connect to a local MongoDB deployment:

val settings = MongoClientSettings.builder()
    .applyConnectionString("mongodb://localhost:27017")
    .build()
val mongoClient = MongoClient.create(settings)

Replica Sets

To connect to a replica set, specify the hostnames (or IP addresses) and port numbers of the replica-set members.

If you aren't able to provide a full list of hosts in the replica set, you can specify one or more of the hosts in the replica set and instruct the Kotlin Sync driver to perform automatic discovery to find the others. To instruct the driver to perform automatic discovery, perform one of the following actions:

• Specify the name of the replica set as the value of the replicaSet parameter.

• Specify false as the value of the directConnection parameter.

• Specify more than one host in the replica set.

The following examples show how to connect to a MongoDB replica set running on port 27017 of three different hosts by using either the ConnectionString or MongoClientSettings class. Select the tab that corresponds to your preferred class.

val mongoClient = MongoClient.create("mongodb://host1:27017,host2:27017,host3:27017/")

val hosts = listOf(
    ServerAddress("host1", 27017),
    ServerAddress("host2", 27017),
    ServerAddress("host3", 27017)
)
val settings = MongoClientSettings.builder()
    .applyToClusterSettings { builder ->
        builder.hosts(hosts)
    }
    .build()
val mongoClient = MongoClient.create(settings)