MongoDB Atlas: Java sync driver connection settings

Java sync driver + Atlas

import com.mongodb.client.MongoClient;
import com.mongodb.client.MongoClients;
import com.mongodb.ConnectionString;
import com.mongodb.MongoClientSettings;
import java.util.concurrent.TimeUnit;

ConnectionString connString = new ConnectionString(System.getenv("MONGODB_URI"));
MongoClientSettings settings = MongoClientSettings.builder()
    .applyConnectionString(connString)
    .applyToConnectionPoolSettings(builder ->
        builder.maxSize(20))
    .applyToSocketSettings(builder ->
        builder.connectTimeout(5, TimeUnit.SECONDS))
    .build();

try (MongoClient client = MongoClients.create(settings)) {
    client.getDatabase("admin").runCommand(new org.bson.Document("ping", 1));
    // use client here; try-with-resources closes it
}

Rules

• Prefer MongoClientSettings.builder() over a bare connection string when you need pool or timeout tuning; applyConnectionString keeps the Atlas SRV parsing.
• One MongoClient per application. It is thread-safe and holds the pool.
• try-with-resources (or an explicit close() on shutdown) releases pooled connections. A leaked client holds sockets open until the server reaps them.
• Set a connect timeout. The default can stall deploys when the network path is wrong.

Verify

The ping at startup confirms URI, credentials, and IP access list before the app serves traffic.

Java driver settings builder pattern and connection string parsing verified against the MongoDB connection string reference at https://www.mongodb.com/docs/manual/reference/connection-string/; Atlas prerequisites per https://www.mongodb.com/docs/atlas/troubleshoot-connection/, checked 2026-09-26.