Is MongoDB written in Java?

Is MongoDB written in Java?

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MongoDB is a NoSQL database that uses a unique architecture and has its own query language, called MongoDB Query Language (MQL). While MongoDB's core storage engine is built on top of C++ code, the majority of its functionality is implemented in C.

To clarify, MongoDB is not written entirely in Java. In fact, Java is only used for a few specific purposes within MongoDB:

However, the core database engine, storage engine, and query processing are written primarily in C++. This allows MongoDB to take advantage of the performance benefits offered by a native implementation. Additionally, the use of C++ enables MongoDB to leverage the vast array of existing libraries and tools available for working with large amounts of data.

The rest of MongoDB's functionality is implemented using various programming languages, including:

In summary, while Java does play a role in the development of MongoDB, it is not the primary language used for building the database itself. C++ remains the foundation upon which MongoDB's core functionality rests.

How to read data from MongoDB in Java?

To read data from MongoDB in Java, you can use the official MongoDB Java Driver. Here's a step-by-step guide:

Step 1: Add the MongoDB Java Driver dependency

In your Maven project (if you're using Maven), add the following dependency to your pom.xml file:

org.mongodb
mongo-java-driver
4.3.1

If you're not using Maven, you can download the driver JAR file from the MongoDB website and add it to your project.

Step 2: Connect to MongoDB

Create a MongoClient instance to connect to your MongoDB database:

String url = "mongodb://localhost:27017/";
MongoClient mongoClient = new MongoClient(new ServerAddress(url));

Replace "localhost:27017" with the URL of your MongoDB server.

Step 3: Get a MongoDB collection

Use the MongoClient instance to get a reference to the desired MongoDB collection:

MongoDatabase database = mongoClient.getDatabase("mydatabase");
MongoCollection collection = database.getCollection("mymycollection");

Replace "mydatabase" and "mymycollection" with the names of your MongoDB database and collection, respectively.

Step 4: Find documents

Use the find() method to retrieve documents from the collection:

FindIterable documents = collection.find(new Document("name", "John"));

This example finds all documents in the collection where the "name" field is equal to "John".

Step 5: Process and print the data

Iterate over the retrieved documents using a MongoCursor:

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

This code will print out each document in the collection that matches the search criteria. You can modify this code to process the data as needed.

Full example

import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.MongoClient;
import com.mongodb.MongoCredential;
import com.mongodb.MongoException;
public class ReadDataFromMongoDB {
public static void main(String[] args) {
String url = "mongodb://localhost:27017/";
MongoClient mongoClient = new MongoClient(new ServerAddress(url));
MongoDatabase database = mongoClient.getDatabase("mydatabase");
MongoCollection collection = database.getCollection("mymycollection");
FindIterable documents = collection.find(new Document("name", "John"));
for (Document document : documents) {
System.out.println(document);
}
// Close the MongoDB client
mongoClient.close();
}
}

This example demonstrates how to read data from a MongoDB collection using the official MongoDB Java Driver. You can modify this code to suit your specific needs.

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