Getting Started with Java Driver — MongoDB Ecosystem
Using the Java driver is very simple. First, be sure to include the driver jar mongo.jar in your classpath. The following code snippets come from the examples/QuickTour.java example code found in the driver.
Making a Connection¶
To make a connection to a MongoDB, you need to have at the minimum, the name of a database to connect to. The database doesn’t have to exist - if it doesn’t, MongoDB will create it for you.
Additionally, you can specify the server address and port when connecting. The following example shows three ways to connect to the database mydb on the local machine :
import com.mongodb.MongoClient; import com.mongodb.MongoException; import com.mongodb.WriteConcern; import com.mongodb.DB; import com.mongodb.DBCollection; import com.mongodb.BasicDBObject; import com.mongodb.DBObject; import com.mongodb.DBCursor; import com.mongodb.ServerAddress; import java.util.Arrays; MongoClient mongoClient = new MongoClient(); // or MongoClient mongoClient = new MongoClient( "localhost" ); // or MongoClient mongoClient = new MongoClient( "localhost" , 27017 ); // or, to connect to a replica set, supply a seed list of members MongoClient mongoClient = new MongoClient(Arrays.asList(new ServerAddress("localhost", 27017), new ServerAddress("localhost", 27018), new ServerAddress("localhost", 27019))); DB db = m.getDB( "mydb" );
At this point, the db object will be a connection to a MongoDB server for the specified database. With it, you can do further operations.
The MongoClient instance actually represents a pool of connections to the database; you will only need one instance of class MongoClient even with multiple threads. See the concurrency doc page for more information.
The MongoClient class is designed to be thread safe and shared among threads. Typically you create only 1 instance for a given database cluster and use it across your application. If for some reason you decide to create many MongoClient instances, note that:
- all resource usage limits (max connections, etc) apply per MongoClient instance
- to dispose of an instance, make sure you call MongoClient.close() to clean up resources