Thursday, October 14, 2010

My First Experience with MongoDB

I know im pretty much slow to this concept of NoSQL. But nevertheless better late than never right ? :) ... So this is my first post on getting my feet wet in the world NoSQL. I have to say coming from a RDMS background it was not much hard to get my self familiar with MongoDB. Ofcourse there are a number of NoSQL implementations out there. But going through each of them MongoDB was the one i felt inclined to go with as the learning curve for me using it was pretty low.

So i was reading through multiple posts, articles to get a feel of what MongoDB can really do. After going through that i wanted to try out an example to get a feel of it. So i first downloded Mongo DB from here.  Im on Ubuntu 8.04 so i downloaded the Linux 32-bit one. They do say about a limitation of using the 32-bit version. But i was not much concerned as this is my stage of getting used to it.

So coming from a J2EE development background mostly using annotations i was inclined to search for a solution using annotations to deal with MongoDB so that the transition from usual JPA/Hibernate mappings to MongoDB will be minimal. I know that the way of thinking in terms of MongoDB is different to the way we map things in a traditional RDMS as there is no concept as foreign keys etc. But i wanted the transition to be minimal. So going on those steps i found this project done by google supporting annotation based mapping facility for the MongoDB called Morphia. This was exactly what i needed.

So i did a quich write up to test it. You need to download Morphia  and also get the Java driver for MongoDB. Next start your mongodb. Go to your MongoDB installation path's bin directory and do as follows;

So i specified the parameters as 

./mongod --dbpath<path_to_your_data_store>;
This starts Mongo DB in its default port. Afterwards i present to you a simple program using the above mentioned libraries.

I have a simple class called MyInfo which has an embedded object called Address. Code is as follows;

import org.bson.types.ObjectId;


public class MyInfo {

    @Id ObjectId id;
    private String name;
    private int age;
    private Address address;
    public ObjectId getId() {
        return id;
    public void setId(ObjectId id) { = id;
    public String getName() {
        return name;
    public void setName(String name) { = name;
    public int getAge() {
        return age;
    public void setAge(int age) {
        this.age = age;
    public Address getAddress() {
        return address;
    public void setAddress(Address address) {
        this.address = address;


public class Address {
    private String adderss1;
    private String address2;

    public String getAdderss1() {
        return adderss1;

    public void setAdderss1(String adderss1) {
        this.adderss1 = adderss1;

    public String getAddress2() {
        return address2;

    public void setAddress2(String address2) {
        this.address2 = address2;

Those were my domain classes. Next i present the main class which does the storing of my objects within the MongoDB.


import com.mongodb.Mongo;
import com.mongodb.MongoException;

 * This class Creates a test Monog Connection and persists an instance of {@linkplain MyInfo}
 * @author dinuka
public class MainMongoPersist {

    public static void main(String[] args) throws UnknownHostException, MongoException {
         * Creates a connection on the local Mongo DB server
        Mongo mon = new Mongo("localhost",27017);
         * Add the classes annotated with @Entity.
         * Note that you do not need to add the Address as we Embedded it within 
         * the MyInfo instance. 
        Morphia morphia = new Morphia();;
         * Create a data source by giving the DB you want to connect to.
        Datastore ds = morphia.createDatastore(mon, "mydb");
        MyInfo inf = new MyInfo();
        Address ad = new Address();
        ad.setAdderss1("No 42");
         * Persist the object

That is it. Now i start my mongo process which allows me to query the DB to check whether the data really did get stored within the DB. So i go to my mongo installation path's bin directory and start a mongo client. Following snippet shows how to do that;

dinuka@dinuka:~/software/mongodb-linux-i686-1.6.3/bin$ ./mongo 
MongoDB shell version: 1.6.3
connecting to: test
> use mydb
switched to db mydb
> db.myInfo.find();
{ "_id" : ObjectId("4cb6d81d166cacce8ab4e4e8"), "className" : "MyInfo", "name" : "Dinuka", "stars" : 1 }
{ "_id" : ObjectId("4cb6d8f71757accef6a9784d"), "className" : "MyInfo", "name" : "Roshan", "stars" : 1 }
{ "_id" : ObjectId("4cb6d910f9d0accee936df12"), "className" : "MyInfo", "name" : "Roshan123", "stars" : 1, "address" : { "adderss1" : "fsdfsdfsd", "address2" : "3424234234" } }

I switched the database as i used the database called mydb which is the one i specified when i created the data source. This is just a basic write up on Mongo DB. There is so much more in it which i am on the verge of learning. As it is a very interesting topic to explore on for me. Up to now the potential i see of using Mongo DB is;

  • It allows you to have a dynamic schema so that adding a column will be no hassle. 
  • You can scale the database with ease using the auto sharding facility provided by MongoDB.
  • I love the fact that you can think in terms of how you map your json data in the front end to the database as it is.
Many more is there which im not familiar with so i rather not comment on anything i do not know :) .. If anyone out there can mention any experience using this in a production system with regards to performance and reliability that would be a great help.

Would love to hear your thoughts/comments on this regards.

And the journey of learning Mongo continues............