Java MongoDB Connection Example

In this tutorial, you will learn how to connect a Java application to a MongoDB database using the latest MongoDB Java Driver. MongoDB is a NoSQL database that’s popular for handling large amounts of data. This guide will help you set up the required dependencies, write a connection program, and test the connection in simple steps.

What You Will Learn:

• How to add the MongoDB Java driver to your project.
• Write a Java program to connect to a MongoDB database.
• Test the connection to MongoDB by running the program.

Technologies Used:

• JDK: Version 1.8 or later (Recommended: Latest version)
• MongoDB: Version 6.0 or later
• MongoDB Java Driver: Version 5.1.4 (latest)

Step 1: Add MongoDB Java Driver Dependency

To connect to MongoDB, you need to add the MongoDB Java Driver to your project.

For Maven Users:

Add the following dependency to your pom.xml file:

<dependency>
    <groupId>org.mongodb</groupId>
    <artifactId>mongodb-driver-sync</artifactId>
    <version>5.1.4</version>
</dependency>

For Gradle Users:

Add the following line to your build.gradle file:

implementation 'org.mongodb:mongodb-driver-sync:5.1.4'

If you don't use Maven or Gradle, you can download the MongoDB Java Driver JAR file from the official website and add it to your project manually.

Step 2: Connect to MongoDB

Make sure that MongoDB is installed and running on your machine. MongoDB usually runs on port 27017. By default, the connection string to MongoDB looks like this:

mongodb://localhost:27017

This connection string connects to a local MongoDB server running on your computer.

Creating a Database in MongoDB:

You don’t need to manually create a database in MongoDB. When you insert data into a collection in MongoDB, it automatically creates the database if it doesn’t exist.

Step 3: Write Java Code to Connect to MongoDB

Here’s a simple Java program that connects to MongoDB and inserts a document into a collection.

Code Example:

import com.mongodb.client.MongoClient;
import com.mongodb.client.MongoClients;
import com.mongodb.client.MongoDatabase;
import org.bson.Document;

public class MongoDBConnectionExample {

    // MongoDB connection URI
    private static final String URI = "mongodb://localhost:27017";

    public static void main(String[] args) {
        // Step 1: Create a MongoClient instance to connect to MongoDB
        try (MongoClient mongoClient = MongoClients.create(URI)) {
            
            // Step 2: Access the database (it will create it if it doesn't exist)
            MongoDatabase database = mongoClient.getDatabase("mydb");

            // Step 3: Confirm the connection
            System.out.println("Connected to the database: " + database.getName());

            // Step 4: Insert a document into a collection
            database.getCollection("testCollection")
                    .insertOne(new Document("name", "Raj").append("age", 30));

            // Step 5: Confirm document insertion
            System.out.println("Inserted a document into the testCollection.");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Explanation:

• Step 1: We use MongoClients.create() to establish a connection to the MongoDB server. The connection URI mongodb://localhost:27017 tells MongoDB to connect to the server running locally on port 27017.

• Step 2: getDatabase("mydb") is used to access the mydb database. If the database does not exist, MongoDB will create it when we insert data.

• Step 3: The program prints the name of the connected database to confirm that the connection was successful.

• Step 4: We insert a new document into the testCollection collection. MongoDB will automatically create this collection if it doesn’t exist. The document contains two fields: name and age.

• Step 5: The program confirms that the document has been inserted.

Step 4: Run the Java Program

After writing the code, run the program. If everything is set up correctly, you will see the following output:

Connected to the database: mydb
Inserted a document into the testCollection.

You'll see an error message if there’s an issue, such as MongoDB not running or an incorrect connection string.

Conclusion

In this tutorial, you learned how to:

• Add the MongoDB Java Driver to your project.
• Write Java code to connect to MongoDB.
• Insert a document into a MongoDB collection.

This simple example can be expanded to include more operations, such as updating or deleting documents or querying collections. MongoDB and Java together offer powerful tools for building scalable applications.