Java MongoDB Drop Collection Example

In this tutorial, we will walk through how to drop a collection from a MongoDB database using Java. Dropping a collection removes it along with all of its data. We will use the MongoDB Java Driver to connect to MongoDB, drop a collection, and verify its deletion.

What You Will Learn:

• How to connect to MongoDB using Java.
• How to drop a collection from a MongoDB database.
• How to confirm the deletion of a collection.

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

You need to include the MongoDB Java Driver in 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’re not using Maven or Gradle, you can download the JAR file from the MongoDB website and manually add it to your classpath.

Step 2: Write Java Code to Drop a MongoDB Collection

Here’s the Java program to connect to MongoDB and drop a collection.

Code Example:

import com.mongodb.client.MongoClient;
import com.mongodb.client.MongoClients;
import com.mongodb.client.MongoDatabase;

public class MongoDBDropCollectionExample {

    // 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: Drop the collection
            database.getCollection("employees").drop();

            // Step 4: Confirm collection drop
            System.out.println("Collection 'employees' dropped successfully from database: " + database.getName());
            
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Explanation with Code Snippets:

• Step 1: Create a MongoClient Instance The MongoClient is used to establish a connection to the MongoDB server. The connection string mongodb://localhost:27017 is used to connect to MongoDB running locally.

  try (MongoClient mongoClient = MongoClients.create(URI)) {
  

  We use a try-with-resources block to ensure the MongoClient is closed automatically after use.

• Step 2: Access the Database The getDatabase() method connects to the mydb database. If the mydb database doesn't exist, MongoDB will create it when needed.

  MongoDatabase database = mongoClient.getDatabase("mydb");
  

  This returns a MongoDatabase object, which allows interaction with the mydb database.

• Step 3: Drop the Collection The drop() method is called on the collection you want to remove. Here, we drop the employees collection from the mydb database.

  database.getCollection("employees").drop();
  

  This will remove the collection and all of its documents from the database.

• Step 4: Confirm Collection Drop After dropping the collection, we print a message to the console confirming that the collection has been successfully dropped.

  System.out.println("Collection 'employees' dropped successfully from database: " + database.getName());
  

Step 3: Run the Java Program

After writing the code, run the program in your IDE or from the command line. If everything is correct, you should see the following output:

Collection 'employees' dropped successfully from database: mydb

If there is an issue, such as MongoDB not running or the collection not existing, an error message will be printed.

Step 4: Verify Collection Deletion

To confirm that the collection has been dropped, use the MongoDB shell or a MongoDB client tool. In the MongoDB shell, you can list all collections in the mydb database with the following commands:

use mydb
show collections

The employees collection should no longer appear in the list.

Conclusion

In this tutorial, you learned how to:

• Connect to MongoDB using Java.
• Drop a collection using the MongoDB Java Driver.
• Verify the deletion of a collection.

Dropping collections is a straightforward operation but should be used with caution, as it permanently deletes all data within the collection. Make sure to back up your data if needed before performing such operations.