mongoDB : Java : Query for a document

This post and sub sequent posts I am going to explain different ways to query for a document.

Find single object from collection

“findOne” method of collection returns a single object from this collection.

> db.employee.find()

{ "_id" : 1, "firstName" : "Joel", "lastName" : "chelli" }

{ "_id" : 2, "firstName" : "Ananad", "lastName" : "Bandaru" }

{ "_id" : 3, "firstName" : "Gopi", "lastName" : "Battu" }

{ "_id" : 4, "firstName" : "Ritwik", "lastName" : "Mohenthy" }

Let’s say I had above data in my employee collection.

import java.net.UnknownHostException;
import com.mongodb.DBObject;
import com.mongodb.MongoClient;
import com.mongodb.DB;
import com.mongodb.DBCollection;

public class FindDocument {

  /* Step 1 : get mongoCLient */
  public static MongoClient getMongoClient(){
    MongoClient mongoClient = null;
     try {
       mongoClient = new MongoClient( "localhost" , 27017 );
    } catch (UnknownHostException e) {
      e.printStackTrace();
    }
     return mongoClient;
  }
  
  public static void main(String args[]){
    MongoClient mongoClient = getMongoClient();
    
    /* Step 2: Connect to DB */
    DB db = mongoClient.getDB("sample");
    
    /*Step 3 : Get collection */
    DBCollection collection = db.getCollection("employee");
    
    /* Step 4 : Get one document */
    DBObject document = collection.findOne();
    
    System.out.println(document);
    
  }
}

Output

{ "_id" : 1.0 , "firstName" : "Joel" , "lastName" : "chelli"}

 

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