Connect to MongoDB

Scala Driver
Tutorials
Connect to MongoDB

Connect to MongoDB

Use MongoClient() to make a connection to a running MongoDB instance.

important

The following examples are not meant to provide an exhaustive list of ways to instantiate MongoClient. For a complete list of MongoClient companion methods, see the MongoClient API documentation.

Note

It is strongly recommended that system keep-alive settings should be configured with shorter timeouts.

See the ‘does TCP keep-alive time affect MongoDB deployments?’ documentation for more information.

Prerequisites

Running MongoDB deployments to which to connect. For example, to connect to a standalone, you must have a running standalone.
The MongoDB Driver. See Installation for instructions on how to install the MongoDB driver.
The following import statements:

import org.mongodb.scala._

import scala.collection.JavaConverters._

`MongoClient`

A MongoClient instance represents a pool of connections to the database; you will only need one instance of class MongoClient even with multiple concurrent operations.

important

Typically you only create one MongoClient instance for a given MongoDB deployment (e.g. standalone, replica set, or a sharded cluster) and use it across your application. However, if you do create multiple instances:

All resource usage limits (e.g. max connections, etc.) apply per MongoClient instance.
To dispose of an instance, call MongoClient.close() to clean up resources.

Connect to a Standalone MongoDB Instance

To connect to a standalone MongoDB instance:

You can create a MongoClient object without any parameters to connect to a MongoDB instance running on localhost on port 27017:
```
val mongoClient = MongoClient()
```
You can explicitly specify the hostname to connect to a MongoDB instance running on the specified host on port 27017:
```
val mongoClient = MongoClient("mongodb://host1")
```

You can explicitly specify the hostname and the port:

val mongoClient = MongoClient("mongodb://host1:27017")

Connect to a Replica Set

To connect to a replica set, you must specify one or more members to the MongoClient apply method.

Note

MongoDB will auto-discover the primary and the secondaries.

You can specify the members using a ConnectionString:
- To specify at least two members of the replica set:

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

With at least one member of the replica set and the replicaSet option specifying the replica set name:

val mongoClient = MongoClient("mongodb://host1:27017,host2:27017,host3:27017/?replicaSet=myReplicaSet")

You can specify a list of the all the replica set members’ ServerAddress:

val mongoClient = MongoClient(
  MongoClientSettings.builder()
    .applyToClusterSettings((builder: ClusterSettings.Builder) => builder.hosts(List(
        new ServerAddress("host1", 27017),
        new ServerAddress("host2", 27017),
        new ServerAddress("host3", 27017)).asJava))
    .build())

Connect to a Sharded Cluster

To connect to a sharded cluster, specify the mongos instance or instances to a MongoClient apply method.

To connect to a single mongos instance:

You can specify the hostname and the port in a ConnectionString

val mongoClient = MongoClient( "mongodb://localhost:27017" )

or leave the connection string out if the mongos is running on localhost:27017:

val mongoClient = MongoClient()

To connect to multiple mongos instances:

You can specify the ConnectionString with their hostnames and ports:

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

You can specify a list of the mongos instances’ ServerAddress:

val mongoClient = MongoClient(
  MongoClientSettings.builder()
    .applyToClusterSettings((builder: ClusterSettings.Builder) => builder.hosts(List(
        new ServerAddress("host1", 27017),
        new ServerAddress("host2", 27017)).asJava))
    .build())

Connection Options

You can specify the connection settings using either the ConnectionString or MongoClientSettings or both.

For example, you can specify TLS/SSL and authentication setting in the connection string:

val mongoClient = MongoClient("mongodb://user1:pwd1@host1/?authSource=db1&ssl=true")

You can also use MongoClientSettings to specify TLS/SSL and the MongoCredential for the authentication information:

val user: String = ???          // the user name
val source: String = ???        // the source where the user is defined
val password: Array[Char] = ??? // the password as a character array
// ...
val credential = MongoCredential.createCredential(user, source, password)

val mongoClient: MongoClient = MongoClient(
  MongoClientSettings.builder()
    .applyToSslSettings((builder: SslSettings.Builder) => builder.enabled(true))
    .applyToClusterSettings((builder: ClusterSettings.Builder) => builder.hosts(List(new ServerAddress("host1", 27017)).asJava))
    .credential(credential)
    .build())

Finally, in some cases you may need to combine a connection string with programmatic configuration:

val connectionString = ConnectionString("mongodb://host1:27107,host2:27017/?ssl=true")
val myCommandListener: CommandListener = ???

val mongoClient = MongoClient( 
  MongoClientSettings.builder()
    .addCommandListener(myCommandListener)
    .applyConnectionString(connectionString)
    .build())

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