MongoDB Tutorial - MongoDB Java

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Download the following code to start coding with Java and MongoDB.

Connect to database

To connect database, specify database name, if database doesn't exist then mongodb creates it automatically.

import com.mongodb.DB;
import com.mongodb.MongoClient;

public class Main{
   public static void main( String args[] ){
      try{   
         MongoClient mongoClient = new MongoClient( "localhost" , 27017 );

         DB db = mongoClient.getDB( "test" );
     System.out.println("Connect to database successfully");
         boolean auth = db.authenticate("myUser", "myPassword".toCharArray());
     System.out.println("Authentication: "+auth);
      }catch(Exception e){
       System.err.println( e.getClass().getName() + ": " + e.getMessage() );
    }
   }
}

Create a collection

To create a collection, use the createCollection() method from com.mongodb.DB class.

import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.MongoClient;

public class Main {
  public static void main(String args[]) {
    try {
      MongoClient mongoClient = new MongoClient("localhost", 27017);
      // Now connect to your databases
      DB db = mongoClient.getDB("test");
      System.out.println("Connect to database successfully");
      boolean auth = db.authenticate("myUserName", "myPassword".toCharArray());
      System.out.println("Authentication: " + auth);
      DBCollection coll = db.createCollection("mycol",null);
      System.out.println("Collection created successfully");
    } catch (Exception e) {
      System.err.println(e.getClass().getName() + ": " + e.getMessage());
    }
  }
}

Getting / selecting a collection

To get/select a collection from the database, use getCollection() method from com.mongodb.DBCollection class.

import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.MongoClient;

public class Main {
  public static void main(String args[]) {
    try {
      MongoClient mongoClient = new MongoClient("localhost", 27017);
      DB db = mongoClient.getDB("test");
      System.out.println("Connect to database successfully");
      boolean auth = db.authenticate("myUserName",
          "myPassword".toCharArray());
      System.out.println("Authentication: " + auth);
      DBCollection coll = db.createCollection("mycol", null);
      System.out.println("Collection created successfully");
      coll = db.getCollection("mycol");
      System.out.println("Collection mycol selected successfully");
    } catch (Exception e) {
      System.err.println(e.getClass().getName() + ": " + e.getMessage());
    }
  }
}

Insert a document

To insert a document into mongodb, use insert() method from DBCollection class.

import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.MongoClient;

public class Main {
  public static void main(String args[]) {
    try {
      MongoClient mongoClient = new MongoClient("localhost", 27017);
      DB db = mongoClient.getDB("test");
      System.out.println("Connect to database successfully");
      boolean auth = db.authenticate("myUserName",
          "myPassword".toCharArray());
      System.out.println("Authentication: " + auth);
      DBCollection coll = db.getCollection("mycol");
      System.out.println("Collection mycol selected successfully");
      BasicDBObject doc = new BasicDBObject("title", "MongoDB")
          .append("description", "database")
          .append("likes", 100)
          .append("url", "http://www.java2s.com");
      coll.insert(doc);
      System.out.println("Document inserted successfully");
    } catch (Exception e) {
      System.err.println(e.getClass().getName() + ": " + e.getMessage());
    }
  }
}

Retrieve all documents

To select all documents from the collection, use find() method from com.mongodb.DBCollection class.

This method returns a cursor, and we can iterate this cursor.

import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.MongoClient;

public class Main {
  public static void main(String args[]) throws Exception {

    MongoClient mongoClient = new MongoClient("localhost", 27017);
    DB db = mongoClient.getDB("test");

    boolean auth = db
        .authenticate("myUserName", "myPassword".toCharArray());
    DBCollection coll = db.getCollection("mycol");
    DBCursor cursor = coll.find();
    int i = 1;
    while (cursor.hasNext()) {
      System.out.println("Inserted Document: " + i);
      System.out.println(cursor.next());
      i++;
    }

  }
}

Update document

To update document from the collection, use update() method from com.mongodb.DBCollection class.

import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.DBObject;
import com.mongodb.MongoClient;

public class Main {
  public static void main(String args[]) throws Exception {
    MongoClient mongoClient = new MongoClient("localhost", 27017);

    DB db = mongoClient.getDB("test");
    boolean auth = db
        .authenticate("myUserName", "myPassword".toCharArray());
    System.out.println("Authentication: " + auth);
    DBCollection coll = db.getCollection("mycol");
    System.out.println("Collection mycol selected successfully");
    DBCursor cursor = coll.find();
    while (cursor.hasNext()) {
      DBObject updateDocument = cursor.next();
      updateDocument.put("likes", "200");
      coll.save(updateDocument);
    }
    System.out.println("Document updated successfully");
    cursor = coll.find();
    int i = 1;
    while (cursor.hasNext()) {
      System.out.println("Updated Document: " + i);
      System.out.println(cursor.next());
      i++;
    }
  }
}

Delete first document

To delete first document from the collection, select the documents using findOne() method and use remove method from com.mongodb.DBCollection class.

import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.DBObject;
import com.mongodb.MongoClient;

public class Main {
  public static void main(String args[]) throws Exception {

    MongoClient mongoClient = new MongoClient("localhost", 27017);
    DB db = mongoClient.getDB("test");
    boolean auth = db
        .authenticate("myUserName", "myPassword".toCharArray());

    DBCollection coll = db.getCollection("mycol");
    System.out.println("Collection mycol selected successfully");
    DBObject myDoc = coll.findOne();
    coll.remove(myDoc);
    DBCursor cursor = coll.find();
    int i = 1;
    while (cursor.hasNext()) {
      System.out.println("Inserted Document: " + i);
      System.out.println(cursor.next());
      i++;
    }
    System.out.println("Document deleted successfully");

  }
}

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