Connect to MongoDB

Create the Application File

Create a file called DemoDataClassExample.kt in your project.

Copy the following sample code into the file and replace the value of the <connection URI string> placeholder with your MongoDB Atlas connection string that you saved in the preceding step.

import com.mongodb.client.model.Filters.eq
import com.mongodb.kotlin.client.MongoClient
// Create data class to represent a MongoDB document
data class Movie(val title: String, val year: Int, val directors: List<String>)
fun main() {
    // Replace the placeholder with your MongoDB deployment's connection string
    val uri = "<connection URI string>"
    val mongoClient = MongoClient.create(uri)
    val database = mongoClient.getDatabase("sample_mflix")
    val collection = database.getCollection<Movie>("movies")
    // Find a document with the specified title
    val doc = collection.find(eq(Movie::title.name, "Before Sunrise")).firstOrNull()
    if (doc != null) {
        // Print the matching document
        println(doc)
    } else {
        println("No matching documents found.")
    }
}

Run the Application

When you run the application, it prints the details of a movie document that matches the query, as shown in the following output:

Movie(title=Before Sunrise, year=1995, directors=[Richard Linklater])

If you don't see any output or receive an error, check whether you included the proper connection string in your application. Also, confirm that you successfully loaded the sample dataset into your MongoDB Atlas cluster.

After completing this step, you have a working application that uses the Kotlin Sync driver to connect to your MongoDB cluster, run a query on the sample data, and print out the result.

Use the Document Class to Model Data (Alternative)

The preceding step demonstrates how to run a query on a sample collection to retrieve data by using a Kotlin data class. This section shows how to use the Document class to store and retrieve data from MongoDB.

In a file called DemoDocumentExample.kt, paste the following sample code to run a query on your sample dataset in MongoDB Atlas. Replace the value of the <connection URI string> placeholder with your MongoDB Atlas connection string:

import com.mongodb.client.model.Filters.eq
import com.mongodb.kotlin.client.MongoClient
import org.bson.Document
fun main() {
    // Replace the placeholder with your MongoDB deployment's connection string
    val uri = "<connection URI string>"
    val mongoClient = MongoClient.create(uri)
    val database = mongoClient.getDatabase("sample_mflix")
    val collection = database.getCollection<Document>("movies")
    // Find a document with the specified title
    val doc = collection.find(eq("title", "Before Sunrise")).firstOrNull()
    if (doc != null) {
        // Print the matching document
        println(doc)
    } else {
        println("No matching documents found.")
    }
}

When you run the application, it prints the details of a movie document that matches the query, as shown in the following output:

Document{{_id=..., plot=A young man and woman ..., genres=[Drama, Romance], ...}}

If you don't see any output or receive an error, check whether you included the proper connection string in your application. Also, confirm that you successfully loaded the sample dataset into your MongoDB Atlas cluster.