MongoDB- Java                                                            

In this article, we’ll take a look at integrating MongoDB (a popular NoSQL database) with Java.

Prerequisites-

You need to make sure that you have MongoDB JDBC driver and Java set up on the machine.

Connect to Database

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

import com.mongodb.client.MongoDatabase; import com.mongodb.MongoClient;  

public class Connect

{ 

    public static void main( String args[] ) 

{        

    // Creating a Mongo client 

    MongoClient mongo = new MongoClient( "localhost" , 27017 );

   //Accessing the database 

    MongoDatabase database = mongo.getDatabase("myDb"); 

System.out.println("Connected !);     

   } 

}

Create a Collection

To create a collection, createCollection()method of

com.mongodb.client.MongoDatabase class is used.

import com.mongodb.client.MongoDatabase; 

import com.mongodb.MongoClient; 

public class CreateCollection

{ 

public static void main( String args[] ) 

{  

   MongoClient mongo = new MongoClient( "localhost" , 27017 ); 

   MongoDatabase database =mongo.getDatabase("myDatabase");  database.createCollection("TestCollection"); 

   System.out.println ("Collection created successfully"); 

   } 

} 

Insert a Document

To insert a document into MongoDB, insert() method of  com.mongodb.client.MongoCollection class is used.

import com.mongodb.client.MongoCollection; 

import com.mongodb.client.MongoDatabase; import org.bson.Document;  

import com.mongodb.MongoClient;   

public class InsertDocument

{ 

public static void main( String args[] ) 

{  

   MongoClient mongo = new MongoClient( "localhost" , 27017 ); 

   MongoDatabase database = mongo.getDatabase("myDatabase");  

   MongoCollection<Document> collection =       database.getCollection("FirstCollection"); 

   Document document = new Document("title", "FirstDocument") 

      .append("id", 1)

      .append("description", "database") 

      .append("likes", 100);

   collection.insertOne(document); 

   System.out.println("Document inserted ");     

   } 

}

Retrieve All Documents

To select documents from the collection, find() method of 

com.mongodb.client.MongoCollection class is used. 

import com.mongodb.client.FindIterable; 

import com.mongodb.client.MongoCollection; 

import com.mongodb.client.MongoDatabase;  import java.util.Iterator; 

import org.bson.Document; 

import com.mongodb.MongoClient;

public class MongoTest

{ 

public static void main( String args[] ) 

{  

   MongoClient mongo = new MongoClient( "localhost" , 27017 ); 

   MongoDatabase database = mongo.getDatabase("myDb");  

   MongoCollection<Document> collection =     database.getCollection("FirstCollection");

   FindIterable<Document> iterDoc = collection.find(); 

   int i = 1;

   Iterator it = iterDoc.iterator(); 

   while (it.hasNext()) 

   {  

         System.out.println(it.next());  

          i++; 

    }

   } 

}

Delete Document

To Delete document we need to use deleteOne() method.

import com.mongodb.client.FindIterable; 

import com.mongodb.client.MongoCollection; 

import com.mongodb.client.MongoDatabase;importcom.mongodb.client.model.Filters;  

import java.util.Iterator; 

import org.bson.Document; 

import com.mongodb.MongoClient;  

public class DeleteDocument

{ 

public static void main( String args[] ) 

{  

MongoClient mongo = new MongoClient( "localhost" , 27017 );

MongoDatabase database = mongo.getDatabase("myDatabase");

MongoCollection<Document> collection = database.getCollection("FirstCollection");

collection.deleteOne(Filters.eq("id", 1)); 

System.out.println("Document deleted successfully...");  

FindIterable<Document> iterDoc = collection.find(); 

int i = 1; 

Iterator it = iterDoc.iterator(); 

while (it.hasNext()) 

  {  

         System.out.println("Inserted Document: "+i);  

         System.out.println(it.next());  

         i++; 

      }       

   } 

}

Update Document

To update a document from the collection, updateOne() method of com.mongodb.client.MongoCollection class is used.

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 UpdateDocument

{ 

public static void main( String args[] ) 

{  

MongoClient mongo = new MongoClient( "localhost" , 27017 ); 

MongoDatabase database = mongo.getDatabase("myDatabase"); 

MongoCollection<Document> collection = database.getCollection("FirstCollection");

collection.updateOne(Filters.eq("id", 1), Updates.set("likes",150));  System.out.println("Document update successfully...");  

FindIterable<Document> iterDoc = collection.find(); 

int i = 1; 

Iterator it = iterDoc.iterator(); 

while (it.hasNext()) 

      { 

        System.out.println(it.next());  

         i++; 

      }     

   } 
}

Thats it for now ! 

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