MongoDB – Java

MongoDB – Java

In this chapter, we will learn how to set up MongoDB CLIENT.

Installation

Before you start using MongoDB in your Java programs, you need to make sure that you have MongoDB CLIENT and Java set up on the machine. You can check Java tutorial for Java installation on your machine. Now, let us check how to set up MongoDB CLIENT.

  • You need to download the jar mongodb-driver-3.11.2.jar and its dependency mongodb-driver-core-3.11.2.jar.. Make sure to download the latest release of these jar files.
  • You need to include the downloaded jar files into your classpath.
    You need to download the jar mongodb-driver-3.11.2.jar and its dependency mongodb-driver-core-3.11.2.jar.. Make sure to download the latest release of these jar files.
    You need to include the downloaded jar files into your classpath.

    Connect to Database

    To connect database, you need to specify the database name, if the database doesn't exist then MongoDB creates it automatically.
    Following is the code snippet to connect to the database −

    import com.mongodb.client.MongoDatabase;
    import com.mongodb.MongoClient;
    import com.mongodb.MongoCredential;
    public class ConnectToDB {
    public static void main( String args[] ) {
    // Creating a Mongo client
    MongoClient mongo = new MongoClient( "localhost" , 27017 );
    // Creating Credentials
    MongoCredential credential;
    credential = MongoCredential.createCredential("sampleUser", "myDb",
    "password".toCharArray());
    System.out.println("Connected to the database successfully");
    // Accessing the database
    MongoDatabase database = mongo.getDatabase("myDb");
    System.out.println("Credentials ::"+ credential);
    }
    }

    Now, let's compile and run the above program to create our database myDb as shown below.

    $javac ConnectToDB.java
    $java ConnectToDB

    On executing, the above program gives you the following output.

    Connected to the database successfully
    Credentials ::MongoCredential{
    mechanism = null,
    userName = 'sampleUser',
    source = 'myDb',
    password = <hidden>,
    mechanismProperties = {}
    }

    Create a Collection

    To create a collection, createCollection() method of com.mongodb.client.MongoDatabase class is used.
    Following is the code snippet to create a collection −

    import com.mongodb.client.MongoDatabase;
    import com.mongodb.MongoClient;
    import com.mongodb.MongoCredential;
    public class CreatingCollection {
    public static void main( String args[] ) {
    // Creating a Mongo client
    MongoClient mongo = new MongoClient( "localhost" , 27017 );
    // Creating Credentials
    MongoCredential credential;
    credential = MongoCredential.createCredential("sampleUser", "myDb",
    "password".toCharArray());
    System.out.println("Connected to the database successfully");
    //Accessing the database
    MongoDatabase database = mongo.getDatabase("myDb");
    //Creating a collection
    database.createCollection("sampleCollection");
    System.out.println("Collection created successfully");
    }
    }

    On compiling, the above program gives you the following result −

    Connected to the database successfully
    Collection created successfully

    Getting/Selecting a Collection

    To get/select a collection from the database, getCollection() method of com.mongodb.client.MongoDatabase class is used.
    Following is the program to get/select a collection −

    import com.mongodb.client.MongoCollection;
    import com.mongodb.client.MongoDatabase;
    import org.bson.Document;
    import com.mongodb.MongoClient;
    import com.mongodb.MongoCredential;
    public class selectingCollection {
    public static void main( String args[] ) {
    // Creating a Mongo client
    MongoClient mongo = new MongoClient( "localhost" , 27017 );
    // Creating Credentials
    MongoCredential credential;
    credential = MongoCredential.createCredential("sampleUser", "myDb",
    "password".toCharArray());
    System.out.println("Connected to the database successfully");
    // Accessing the database
    MongoDatabase database = mongo.getDatabase("myDb");
    // Creating a collection
    System.out.println("Collection created successfully");
    // Retrieving a collection
    MongoCollection<Document> collection = database.getCollection("myCollection");
    System.out.println("Collection myCollection selected successfully");
    }
    }

    On compiling, the above program gives you the following result −

    Connected to the database successfully
    Collection created successfully
    Collection myCollection selected successfully

    Insert a Document

    To insert a document into MongoDB, insert() method of com.mongodb.client.MongoCollection class is used.
    Following is the code snippet to insert a document −

    import com.mongodb.client.MongoCollection;
    import com.mongodb.client.MongoDatabase;
    import org.bson.Document;
    import com.mongodb.MongoClient;
    public class InsertingDocument {
    public static void main( String args[] ) {
    // Creating a Mongo client
    MongoClient mongo = new MongoClient( "localhost" , 27017 );
    // Accessing the database
    MongoDatabase database = mongo.getDatabase("myDb");
    // Creating a collection
    database.createCollection("sampleCollection");
    System.out.println("Collection created successfully");
    // Retrieving a collection
    MongoCollection<Document> collection = database.getCollection("sampleCollection");
    System.out.println("Collection sampleCollection selected successfully");
    Document document = new Document("title", "MongoDB")
    .append("description", "database")
    .append("likes", 100)
    .append("url", "https://prutor.ai/mongodb/")
    .append("by", "prutor");
    //Inserting document into the collection
    collection.insertOne(document);
    System.out.println("Document inserted successfully");
    }

    On compiling, the above program gives you the following result −

    Connected to the database successfully
    Collection sampleCollection selected successfully
    Document inserted successfully

    Retrieve All Documents

    To select all documents from the collection, find() method of com.mongodb.client.MongoCollection class is used. This method returns a cursor, so you need to iterate this cursor.
    Following is the program to select all documents −

    import com.mongodb.client.FindIterable;
    import com.mongodb.client.MongoCollection;
    import com.mongodb.client.MongoDatabase;
    import java.util.ArrayList;
    import java.util.Iterator;
    import java.util.List;
    import org.bson.Document;
    import com.mongodb.MongoClient;
    import com.mongodb.MongoCredential;
    public class RetrievingAllDocuments {
    public static void main( String args[] ) {
    // Creating a Mongo client
    MongoClient mongo = new MongoClient( "localhost" , 27017 );
    // Creating Credentials
    MongoCredential credential;
    credential = MongoCredential.createCredential("sampleUser", "myDb", "password".toCharArray());
    System.out.println("Connected to the database successfully");
    // Accessing the database
    MongoDatabase database = mongo.getDatabase("myDb");
    // Retrieving a collection
    MongoCollection<Document> collection = database.getCollection("sampleCollection");
    System.out.println("Collection sampleCollection selected successfully");
    Document document1 = new Document("title", "MongoDB")
    .append("description", "database")
    .append("likes", 100)
    .append("url", "https://prutor.ai/mongodb/")
    .append("by", "prutor");
    Document document2 = new Document("title", "RethinkDB")
    .append("description", "database")
    .append("likes", 200)
    .append("url", "https://prutor.ai/rethinkdb/")
    .append("by", "prutor");
    List<Document> list = new ArrayList<Document>();
    list.add(document1);
    list.add(document2);
    collection.insertMany(list);
    // Getting the iterable object
    FindIterable<Document> iterDoc = collection.find();
    int i = 1;
    // Getting the iterator
    Iterator it = iterDoc.iterator();
    while (it.hasNext()) {
    System.out.println(it.next());
    i++;
    }
    }
    }

    On compiling, the above program gives you the following result −

    Connected to the database successfully
    Collection sampleCollection selected successfully
    Document{{_id=5dce4e9ff68a9c2449e197b2, title=MongoDB, description=database, likes=100, url=https://prutor.ai/mongodb/, by=prutor}}
    Document{{_id=5dce4e9ff68a9c2449e197b3, title=RethinkDB, description=database, likes=200, url=https://prutor.ai/rethinkdb/, by=prutor}}

    Update Document

    To update a document from the collection, updateOne() method of com.mongodb.client.MongoCollection class is used.
    Following is the program to select the first document −

    import com.mongodb.client.FindIterable;
    import com.mongodb.client.MongoCollection;
    import com.mongodb.client.MongoDatabase;
    import com.mongodb.client.model.Filters;
    import com.mongodb.client.model.Updates;
    import java.util.Iterator;
    import org.bson.Document;
    import com.mongodb.MongoClient;
    import com.mongodb.MongoCredential;
    public class UpdatingDocuments {
    public static void main( String args[] ) {
    // Creating a Mongo client
    MongoClient mongo = new MongoClient( "localhost" , 27017 );
    // Creating Credentials
    MongoCredential credential;
    credential = MongoCredential.createCredential("sampleUser", "myDb",
    "password".toCharArray());
    System.out.println("Connected to the database successfully");
    // Accessing the database
    MongoDatabase database = mongo.getDatabase("myDb");
    // Retrieving a collection
    MongoCollection<Document> collection = database.getCollection("sampleCollection");
    System.out.println("Collection myCollection selected successfully");
    collection.updateOne(Filters.eq("title", 1), Updates.set("likes", 150));
    System.out.println("Document update successfully...");
    // Retrieving the documents after updation
    // Getting the iterable object
    FindIterable<Document> iterDoc = collection.find();
    int i = 1;
    // Getting the iterator
    Iterator it = iterDoc.iterator();
    while (it.hasNext()) {
    System.out.println(it.next());
    i++;
    }
    }
    }

    On compiling, the above program gives you the following result −

    Connected to the database successfully
    Collection myCollection selected successfully
    Document update successfully...
    Document{{_id=5dce4e9ff68a9c2449e197b2, title=MongoDB, description=database, likes=100, url=https://prutor.ai/mongodb/, by=prutor}}
    Document{{_id=5dce4e9ff68a9c2449e197b3, title=RethinkDB, description=database, likes=200, url=https://prutor.ai/rethinkdb/, by=prutor}}

    Delete a Document

    To delete a document from the collection, you need to use the deleteOne() method of the com.mongodb.client.MongoCollection class.
    Following is the program to delete a document −

    import com.mongodb.client.FindIterable;
    import com.mongodb.client.MongoCollection;
    import com.mongodb.client.MongoDatabase;
    import com.mongodb.client.model.Filters;
    import java.util.Iterator;
    import org.bson.Document;
    import com.mongodb.MongoClient;
    import com.mongodb.MongoCredential;
    public class DeletingDocuments {
    public static void main( String args[] ) {
    // Creating a Mongo client
    MongoClient mongo = new MongoClient( "localhost" , 27017 );
    // Creating Credentials
    MongoCredential credential;
    credential = MongoCredential.createCredential("sampleUser", "myDb",
    "password".toCharArray());
    System.out.println("Connected to the database successfully");
    // Accessing the database
    MongoDatabase database = mongo.getDatabase("myDb");
    // Retrieving a collection
    MongoCollection<Document> collection = database.getCollection("sampleCollection");
    System.out.println("Collection sampleCollection selected successfully");
    // Deleting the documents
    collection.deleteOne(Filters.eq("title", "MongoDB"));
    System.out.println("Document deleted successfully...");
    // Retrieving the documents after updation
    // Getting the iterable object
    FindIterable<Document> iterDoc = collection.find();
    int i = 1;
    // Getting the iterator
    Iterator it = iterDoc.iterator();
    while (it.hasNext()) {
    System.out.println(it.next());
    i++;
    }
    }
    }

    On compiling, the above program gives you the following result −

    Connected to the database successfully
    Collection sampleCollection selected successfully
    Document deleted successfully...
    Document{{_id=5dce4e9ff68a9c2449e197b3, title=RethinkDB, description=database, likes=200, url=https://prutor.ai/rethinkdb/, by=prutor}}

    Dropping a Collection

    To drop a collection from a database, you need to use the drop() method of the com.mongodb.client.MongoCollection class.
    Following is the program to delete a collection −

    import com.mongodb.client.MongoCollection;
    import com.mongodb.client.MongoDatabase;
    import org.bson.Document;
    import com.mongodb.MongoClient;
    import com.mongodb.MongoCredential;
    public class DropingCollection {
    public static void main( String args[] ) {
    // Creating a Mongo client
    MongoClient mongo = new MongoClient( "localhost" , 27017 );
    // Creating Credentials
    MongoCredential credential;
    credential = MongoCredential.createCredential("sampleUser", "myDb",
    "password".toCharArray());
    System.out.println("Connected to the database successfully");
    // Accessing the database
    MongoDatabase database = mongo.getDatabase("myDb");
    // Creating a collection
    System.out.println("Collections created successfully");
    // Retrieving a collection
    MongoCollection<Document> collection = database.getCollection("sampleCollection");
    // Dropping a Collection
    collection.drop();
    System.out.println("Collection dropped successfully");
    }
    }

    On compiling, the above program gives you the following result −

    Connected to the database successfully
    Collection sampleCollection selected successfully
    Collection dropped successfully

    Listing All the Collections

    To list all the collections in a database, you need to use the listCollectionNames() method of the com.mongodb.client.MongoDatabase class.
    Following is the program to list all the collections of a database −

    import com.mongodb.client.MongoDatabase;
    import com.mongodb.MongoClient;
    import com.mongodb.MongoCredential;
    public class ListOfCollection {
    public static void main( String args[] ) {
    // Creating a Mongo client
    MongoClient mongo = new MongoClient( "localhost" , 27017 );
    // Creating Credentials
    MongoCredential credential;
    credential = MongoCredential.createCredential("sampleUser", "myDb",
    "password".toCharArray());
    System.out.println("Connected to the database successfully");
    // Accessing the database
    MongoDatabase database = mongo.getDatabase("myDb");
    System.out.println("Collection created successfully");
    for (String name : database.listCollectionNames()) {
    System.out.println(name);
    }
    }
    }

    On compiling, the above program gives you the following result −

    Connected to the database successfully
    Collection created successfully
    myCollection
    myCollection1
    myCollection5

    Remaining MongoDB methods save(), limit(), skip(), sort() etc. work same as explained in the subsequent tutorial.

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