BE THE CODER > No SQL > Mongo DB Examples > How to query a Collection

MongoDB is a scalable, high-performance, open source NoSQL database. It offers Ad hoc queries, Indexing, Replication, Load balancing, File storage (GridFS), Aggregation, MapReduce and Server-side JavaScript execution. This requires the library mongo-2.8.0.jar to be present in the classpath. The following example shows how to query a collection.

File Name :	com/bethecoder/tutorials/mongodb/tests/QueryTest.java
Author :	Sudhakar KV
Email :	[email protected]


package com.bethecoder.tutorials.mongodb.tests;



import java.net.UnknownHostException;



import com.mongodb.BasicDBObject;

import com.mongodb.BasicDBObjectBuilder;

import com.mongodb.DB;

import com.mongodb.DBCollection;

import com.mongodb.DBCursor;

import com.mongodb.DBObject;

import com.mongodb.Mongo;

import com.mongodb.MongoException;



public class QueryTest {



  /**

   * @param args

   */

  public static void main(String[] args) {



    try {

      //Connect to mongoDB with given IP and PORT

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

      

      //Get the database object

      DB database = mongo.getDB("mytestdb");

      

      //Gets a collection with a given name.

      DBCollection collection = database.getCollection("mynums");



      //Query for  (num > 2 && num < 9) && (even==true)

      DBObject query = new BasicDBObject();

      query.put("num", BasicDBObjectBuilder.start().add("$gt", 2).add("$lt", 9).get()); 

      query.put("even", true);

      

      //Queries for all objects in this collection

      DBCursor dbCursor = collection.find(query);

      DBObject record = null;

      

      while (dbCursor.hasNext()) {

        record = dbCursor.next();

        System.out.println(record);

      }

      

    } catch (UnknownHostException e) {

      e.printStackTrace();

    } catch (MongoException e) {

      e.printStackTrace();

    }

  }

}