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 the MongoClient constructors, see MongoClient() API documentation.

Note

The 3.5 release deprecated socket keep-alive settings, also socket keep-alive checks are now on by default. 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 com.mongodb.MongoClient;
    import com.mongodb.MongoClientURI;
    import com.mongodb.ServerAddress;
    import com.mongodb.MongoCredential;
    import com.mongodb.MongoClientOptions;
    
    import java.util.Arrays;
    

MongoClient

The MongoClient() instance represents a pool of connections to the database; you will only need one instance of class MongoClient even with multiple threads.

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 instantiate a MongoClient object without any parameters to connect to a MongoDB instance running on localhost on port 27017:

    MongoClient mongoClient = new MongoClient();
    
  • You can explicitly specify the hostname to connect to a MongoDB instance running on the specified host on port 27017:

    MongoClient mongoClient = new MongoClient( "host1" );
    
  • You can explicitly specify the hostname and the port:

    MongoClient mongoClient = new MongoClient( "host1" , 27017 );
    
  • You can specify the MongoClientURI connection string.

    MongoClient mongoClient = new MongoClient(new MongoClientURI("mongodb://host1:27017"));
    

Connect to a Replica Set

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

Note

MongoDB will auto-discover the primary and the secondaries.

  • You can specify the members using the MongoClientURI connection string:

    • To specify at least two members of the replica set:

      MongoClient mongoClient = new MongoClient(
          new MongoClientURI("mongodb://host1:27017,host2:27017,host3:27017"));
      
    • With at least one member of the replica set and the replicaSet option:

      MongoClient mongoClient = new MongoClient(
          new MongoClientURI(
            "mongodb://host1:27017,host2:27017,host3:27017/?replicaSet=myReplicaSet"));
      
  • You can specify a list of the all the replica set members’ ServerAddress:

    MongoClient mongoClient = new MongoClient(
    Arrays.asList(new ServerAddress("host1", 27017),
                  new ServerAddress("host2", 27017),
                  new ServerAddress("host3", 27017)));
    

Connect to a Sharded Cluster

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

To connect to a single mongos instance:

  • You can specify the hostname and the port (or you can omit the parameters if mongos is running on localhost and port 27017)

    MongoClient mongoClient = new MongoClient( "localhost" , 27017 );
    
  • You can specify the MongoClientURI connection string:

    MongoClient mongoClient = new MongoClient(new MongoClientURI("mongodb://localhost:27017"));
    

To connect to multiple mongos instances:

  • You can specify the MongoClientURI connection string with their hostnames and ports:

    MongoClient mongoClient = new MongoClient(
       new MongoClientURI("mongodb://host1:27017,host2:27017"));
    
  • You can specify a list of the mongos instances’ ServerAddress:

    MongoClient mongoClient = new MongoClient(
       Arrays.asList(new ServerAddress("host1", 27017),
                     new ServerAddress("host2", 27017)));
    

Connection Options

You can specify the connection settings using either the MongoClientURI or MongoClientOptions or both.

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

MongoClientURI uri = new MongoClientURI("mongodb://user1:pwd1@host1/?authSource=db1&ssl=true");
MongoClient mongoClient = new MongoClient(uri);

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


 String user; // the user name
 String database; // the name of the database in which the user is defined
 char[] password; // the password as a character array
 // ...

 MongoCredential credential = MongoCredential.createCredential(user, database, password);

 MongoClientOptions options = MongoClientOptions.builder().sslEnabled(true).build();

 MongoClient mongoClient = new MongoClient(new ServerAddress("host1", 27017),
                                           Arrays.asList(credential),
                                           options);