CRUD operations in Java MongoDB

16 Oct 2023

mongoDB

MongoDB, a no-SQL database, provides a flexible and scalable solution for storing and retrieving data. In this blog post, we will explore how to perform CRUD (Create, Read, Update, Delete) operations in MongoDB using Java.

Prerequisites

Before diving into the CRUD operations, make sure you have the following set up in your environment:

MongoDB installed and running
Java SDK installed

Connect to the MongoDB Database

To establish a connection with the MongoDB database, we need to use the MongoDB Java driver. You can include the driver in your Java project using Maven or by downloading the JAR file directly.

Here’s an example of how to connect to a MongoDB database using Java:

import com.mongodb.client.MongoClients;
import com.mongodb.client.MongoClient;
	
public class MongoDBConnection {
    public static void main(String[] args) {
        MongoClient mongoClient = MongoClients.create("mongodb://localhost:27017");
        
        // Perform CRUD operations here
        
        mongoClient.close();
    }
}

Create Document (Insert)

To insert a document into MongoDB, we need to create a Document object and insert it into the desired collection. Here’s an example:

import org.bson.Document;
import com.mongodb.client.MongoCollection;
	
// Assuming you already have a MongoClient object
MongoCollection<Document> collection = mongoClient.getDatabase("mydb").getCollection("mycollection");

Document document = new Document("name", "John Doe")
                        .append("age", 30)
                        .append("email", "john.doe@example.com");

collection.insertOne(document);

Read Documents

To retrieve documents from MongoDB, we can use the find method to get a cursor for the matching documents. Here’s an example:

import org.bson.Document;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.FindIterable;

// Assuming you already have a MongoClient object and a MongoCollection object
FindIterable<Document> documents = collection.find();

for (Document document : documents) {
    System.out.println(document.toJson());
}

Update Document

To update a document in MongoDB, we use the updateOne method and specify the filter criteria and the update operation. Here’s an example:

import org.bson.Document;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.UpdateResult;
import static com.mongodb.client.model.Filters.eq;
import static com.mongodb.client.model.Updates.set;

// Assuming you already have a MongoClient object and a MongoCollection object
UpdateResult result = collection.updateOne(eq("name", "John Doe"), set("age", 35));

System.out.println("Modified documents: " + result.getModifiedCount());

Delete Document

To delete a document from MongoDB, we use the deleteOne method and specify the filter criteria. Here’s an example:

import org.bson.Document;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.DeleteResult;
import static com.mongodb.client.model.Filters.eq;

// Assuming you already have a MongoClient object and a MongoCollection object
DeleteResult result = collection.deleteOne(eq("name", "John Doe"));

System.out.println("Deleted documents: " + result.getDeletedCount());

Conclusion

In this blog post, we’ve seen how to perform CRUD operations in MongoDB using Java. Remember to handle exceptions and close the MongoDB connection properly. MongoDB’s flexibility and scalability make it a great choice for modern application development.

To learn more about MongoDB and its Java driver, refer to the official documentation:

#mongoDB #Java