MongoDB for dummies

February 17, 2016

 

I know I started this blog with several tips for advanced users, but let's get back to some of the basics of MongoDB.

I am more familiar with the python MongoDB client, but this time will use the most common driver, the Java client.

This allows us to explore the common and the differences between the clients.

This tutorial will cover the following topics:

 

  • Installation

  • Shell commands

  • Atom Installation

  • Hello world with mongo

  • Basic terminology

  • Overview of multiple JVM libraries.

MongoDB Installation:

Best updated and thorough explanation can be found here, but for our purpose, this tutorial will use version 3.2 of MongoDB. we'll use the following for Ubunto 14.04 LTS:

 

 

1. sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv EA312927

2. echo "deb http://repo.mongodb.org/apt/ubuntu trusty/mongodb-org/3.2 multiverse" | sudo tee /etc/apt/sources.list.d/mongodb-org-3.2.list

3. sudo apt-get update

4. sudo apt-get install -y mongodb-org

After installation let's run it

 

5. sudo service mongod start

 

Shell and MongoDB commands:

Now, after the setup part, need to verify the installation is actually working, in order to do so run:

ps aux | grep mongo

Verify that the grep returns a process which is not the grep itself.

 

let's connect to the MongoDB service, there is a simple console application named surprisingly, mongo.

>mongo

 

you should see:

 

 

 

Now, the most basic component is the db parameter, through it we can access other collections and documents. For example:

 

 

 

The shell is one of the most important building blocks, since most of MongoDB documentation is usually referring to the shell commands. Most shell commands can be done using either one of the clients but when understanding the shell it is much more easier to delve into the MongoDB documentation.

 

Security Notes:

In order to use mongo remotely, remove bind_ip: 127.0.0.1 from /etc/mongod.conf

In order to use mongo in a better way please consider using the authorization mechanism and adding the SSL connection.

Atom Installation

Each one has his preferred IDE, personally I am a fan of vi, so I am using atom.

Let's set it up:

  1.  Windows: Download from atom

  2.  Mac: Download from atom

  3.  Linux: 

    1. download atom-amd64.deb from the Atom releases page.

    2. Run sudo dpkg --install atom-amd64.deb on the package

Hello World

 

Let's verify we have all the dependencies, if you would like to get one of the official java driver, it can be found here

Let's connect our simple application with MongoDB:

 

import com.mongodb.MongoClient;

import com.mongodb.client.MongoCollection;

import com.mongodb.client.MongoDatabase;

import org.bson.Document;

import com.mongodb.client.FindIterable;

Client mongoClient = new MongoClient(new MongoClientURI("mongodb://localhost:27017"));

MongoDatabase database = mongoClient.getDB("Tutorial");

MongoCollection collection = database.getCollection("customers");

Document person = new Document("_id", 1213456789) .append("name", "John Dough") .append("address", new Document("street", "Over the rainbow St") .append("city", "Somewhere") .append("state", "CA") .append("zip", 88888)); collection.insert(person);

Document query = new Document("_id", 1213456789);

FindIterable<Document> iterable = collection.find(query);

Document person = iterable.first();

 

Let's explain this code:

First, we create a connection with the URI connection string to local host, with port 27017.

Then, we connect to Database named Tutorial And use a collection named customers .

This is the basic hello world application in mongo, being able to connect to the server.

Basic Operations

 

Let's explain some of the basic operations we just used, if you have the background of SQL, then the correlation between it and Mongo is the following:

Database == Database

Collection == Table

Document == Row

Let's get back to the example of code we just used.

Then we create a person with the name John Dough  and some other details and insert it into the database

This is how we insert and populate our database.

 

Databases has one more trick off its sleeve, query!. our next operation is to query for the same document,

We create an object which represent our search, and we use it with the find method. the find method returns a finditerable object, which represent the dataset of results of our search.

Accessing it can be done using forEach.

Exceptions

There are many JVM libraries, when using the official package com.mongo there is an important pitfall, handling exceptions, for example when the connection string is not a valid server, you would expect to catch it with MongoException/RuntimeException but this does not seem to work. The exception is NullPointerException. stack overflow link. More JVM libraries will be discussed in the next topic.

JVM common libraries

 

There are several good JVM libraries available around, each has its pros and cons:

 

  1. MongoDB Java driver - Official, easy to use and provide up to date mechanisms.

  2. Jongo - Best when using Jackson in your application

  3. Morphia - an annotation driver.

  4. Spring Data - Doesn;t support GeoJSON properly

 

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