MongoDB is an open-source cross-platform document database developed using C++. Some features of MongoDB are:
- High and effective performance
- Easily scalable
- High availability
- It can store high volume of data
It contains data in the form of collections and documents instead of rows and tables. A collection is a set of documents. The collection does not have schemas. It represents data in the form of a hierarchical model with which the storage of arrays and other data structures will be easy.
Components of MongoDB
The essentials components of MongoDB are listed below:
- id: This field represents a unique field in MongoDB. This field is created by default.
- Collection: It is a set of MongoDB documents. It exists with a single database.
- Database: This is the container for collections. Multiple databases can be stored in a mongoDB server.
- Document: A record in mongoDB is called a document. It contains names and values.
- Field: It is a name-value pair in a document.
Note: Make sure to install and setup MongoDB JDBC driver and Java.
Table of contents: 1. Establishing connections to database 2. Creating a MongoDb collection 3. Getting a Collection 4. Inserting Values into MongoDb 5. Displaying the list of all Documents 6. Updating documents in the MongoDB 7. Deleting a Document 8. Dropping of a Collection 9. Displaying all the collections
Establishing connections to database
For making the connection, you have to mention the database name. MongoDB creates a database by default if no name is mentioned.
- Firstly, import the required libraries for establishing the connection.
- Here, “MongoClient” is used to create the client for the database.
- “MongoCredential” is used for creating the credentials.
- And finally, to access the database “MongoDatabase” is used.
- Username will be: “GFGUser” and the database name will be “mongoDb“.
- The function “.toCharArray()” is used to convert the password into a character array.
- The function “.getDatabase()” is used for getting the database.
The following code establishes a connection to MongoDB ->
Java
// Java program for establishing connections// to MongoDbimport com.mongodb.client.MongoDatabase;import com.mongodb.MongoClient;import com.mongodb.MongoCredential;public class ConnectionDB { public static void establishConnections() { try { MongoClient db = new MongoClient("localhost", 27017); MongoCredential credential; credential = MongoCredential .createCredential( "GFGUser", "mongoDb", "password".toCharArray()); System.out.println( "Successfully Connected" + " to the database"); MongoDatabase database = db.getDatabase("mongoDb"); System.out.println("Credentials are: " + credential); } catch (Exception e) { System.out.println( "Connection establishment failed"); System.out.println(e); } }} |
Output: 
Creating a MongoDb collection:
To create a collection com.mongodb.client.MongoDatabase class and createCollection() method is used. Here, “database.createCollection()” creates a collection named as “GFGCollection”. Following is the code for creating collection:
Java
// Java program to create a MongoDb collectionimport com.mongodb.client.MongoDatabase;import com.mongodb.MongoClient;import com.mongodb.MongoCredential;public class Collection { public static void createCollection( String collectionName) { try { // establishConnections() Code // is defined above establishConnections(); // Get the database instance MongoDatabase database = db.getDatabase("mongoDb"); // Create the collection database.createCollection(collectionName); System.out.println( "Collection created Successfully"); } catch (Exception e) { System.out.println( "Collection creation failed"); System.out.println(e); } }} |
Output: 
Getting a Collection
For getting a collection, MongoCollection.getCollection() method is used. Below is the implementation of this approach:
Java
// Java program to retrieve a MongoDb collectionimport com.mongodb.client.MongoDatabase;import com.mongodb.MongoClient;import com.mongodb.MongoCredential;public class Collection { public static void getCollection( String collectionName) { try { // establishConnections() Code // is defined above establishConnections(); // Retrieve the collection MongoCollection<Document> collection = database .getCollection(collectionName); System.out.println( "Collection retrieved Successfully"); } catch (Exception e) { System.out.println( "Collection retrieval failed"); System.out.println(e); } }} |
Output 
Inserting Values into MongoDb
Only a document type of data can be inserted a MongoDB. Therefore, either we can create a document with the values to be inserted using append() method or pass a document directly into the MongoDB using .insert() method. Here, first, we created a new document as “title” and then append the “about” section. Then, we have given the respective values to the documents. The function “.insertOne()” is used to insert the document into the collection. Below is the implementation of this approach:
Java
// Java program to insert values into MongoDBimport com.mongodb.client.MongoDatabase;import com.mongodb.MongoClient;import com.mongodb.MongoCredential;public class Collection { // Function to insert only one // document in to the MongoDB public static void insertADocIntoDb() { try { // establishConnections() Code // is defined above establishConnections(); // Creating the document // to be inserted Document document = new Document("title", "MongoDB") .append("about", "Open-Source database") // Insert the document collection.insertOne(document); System.out.println( "Document inserted Successfully"); } catch (Exception e) { System.out.println( "Document insertion failed"); System.out.println(e); } } // Function to insert multiple // documents in to the MongoDB public static void insertManyDocsIntoDb() { try { // establishConnections() Code // is defined above establishConnections(); // Creating the document // to be inserted Document document = new Document("title", "MongoDB") .append("about", "Open-Source database"); Document document1 = new Document("title", "retrieveDb") .append("about", "Open-source database"); // Adding the documents into a list List<Document> dblist = new ArrayList<Document>(); dblist.add(document); dblist.add(document1); // Insert the list of documents into DB collection.insertMany(dblist); System.out.println( "Documents inserted Successfully"); } catch (Exception e) { System.out.println( "Documents insertion failed"); System.out.println(e); } }} |
Output: 
Displaying the list of all Documents
For displaying all documents of collection, find() method is used. Here, the database has two documents namely “document” and “document1”, which are retrieved using find() method. We use an iterator since it will iterate over each document present in the list and display it to us. Following is code for displaying all the documents:
Java
// Java code to display documents from DBimport com.mongodb.client.MongoDatabase;import com.mongodb.MongoClient;import com.mongodb.MongoCredential;public class Collection { public static void displayDocuments() { try { // establishConnections() Code // is defined above establishConnections(); System.out.println( "Displaying the list" + " of Documents"); // Get the list of documents from the DB FindIterable<Document> iterobj = collection.find(); // Print the documents using iterators Iterator itr = iterobj.iterator(); while (itr.hasNext()) { System.out.println(itr.next()); } } catch (Exception e) { System.out.println( "Could not find the documents " + "or No document exists"); System.out.println(e); } }} |
Output: 
Updating documents in the MongoDb
For updating the document, updateOne() method is used. Here, “Filters.eq” creates a filter that matches all documents with the name provided as argument. “Updates.set()” is used to update the document as the given value in the argument. Following is the code for it:
Java
// Java code to update the documents in DBimport com.mongodb.client.MongoDatabase;import com.mongodb.MongoClient;import com.mongodb.MongoCredential;public class Collection { public static void updateDocuments() { try { // establishConnections() Code // is defined above establishConnections(); MongoDatabase database = mongo.getDatabase("mongoDb"); MongoCollection<Document> collection = database.getCollection( "GFGCollection"); collection.updateOne( Filters.eq("title", "MongoDB"), Updates.set("about", "Database")); System.out.println( "Successfully updated" + " the document"); } catch (Exception e) { System.out.println( "Updation failed"); System.out.println(e); } }} |
Output: 
Deleting a Document
For deleting the document, deleteOne() method is used. Following is the code for deleting the document ->
Java
// Java code to update the documents in DBimport com.mongodb.client.MongoDatabase;import com.mongodb.MongoClient;import com.mongodb.MongoCredential;public class Collection { public static void deleteDocuments() { try { // establishConnections() Code // is defined above establishConnections(); MongoDatabase database = mongo.getDatabase("mongoDb"); MongoCollection<Document> collection = database.getCollection( "GFGCollection"); collection.deleteOne( Filters.eq("title", "Open-Source Database")); System.out.println( "Successfully deleted" + " the document"); } catch (Exception e) { System.out.println( "Deletion failed"); System.out.println(e); } }} |
Output: 
Dropping of a Collection
“Collection.drop()” is used to drop the created collection. Following is the code for dropping the collection:
Java
// Java code to drop a collection in MongoDbimport com.mongodb.client.MongoDatabase;import com.mongodb.MongoClient;import com.mongodb.MongoCredential;public class Collection { public static void dropACollection() { try { // establishConnections() Code // is defined above establishConnections(); // Get the collection MongoCollection<Document> collection = database .getCollection( "GFGCollection"); // Drop the above collection collection.drop(); System.out.println( "Successfully dropped" + " collection"); } catch (Exception e) { System.out.println( "Drop failed"); System.out.println(e); } }} |
Output: 
Displaying all the collections
For displaying the list of all collections, listCollectionNames() method is used. Here, we iterate over all the collections we created with the help of “for()” statement. Database.listCollectionNames() is used to display the list of all collections present in the database. Following is the code for displaying all the collections:
Java
// Java code to display all collectionsimport com.mongodb.client.MongoDatabase;import com.mongodb.MongoClient;import com.mongodb.MongoCredential;public class Collection { public static void displayCollections() { try { // establishConnections() Code // is defined above establishConnections(); MongoDatabase database = mongo.getDatabase("mongoDb"); System.out.println( "Displaying the list" + " of all collections"); MongoCollection<Document> collection = database.getCollection( "GFGCollection"); for (String allColl : database .listCollectionNames()) { System.out.println(allColl); } } catch (Exception e) { System.out.println( "Collections display failed"); System.out.println(e); } }} |
Output: 
