Web Applications using MongoDB – MongoDB is one of the best tools for serious web developers. This article on MongoDB will look at everything you need to know to build web applications with MongoDB. But before we begin, let’s take a closer look at the popular tool.
What is MongoDB?
In the simplest terms, MongoDB is a cross-platform document-oriented NoSQL database that uses JSON-like documents using dynamic schemas, called BSON documents, instead of following the conventional relational database (RDB) structure.
That’s a lot of terms that you may not be familiar with, so let’s break them down first.
A document-oriented database functions on the basic concept that a data document contains ‘metadata’, which are values used to identify the type of data and make it easier to store and retrieve when needed. For instance, let’s look at the following two lines of data:
- John Hancock
- Architect
A look at these two lines should give you an idea of what this data refers to a person’s name and occupation. A machine, however, cannot make out this distinction. It needs to be told about the type of data.
In an RDB, this type can be stored in a key-value store that’s separate from the document itself. However, with a document-oriented database, you get to determine the type of data as you type the code. So you end up writing a bit like this:
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- <name> John Hancock </name>
- <occupation> Architect </occupation>
And there you go; now the type of data has been defined right within the document. This gives a flexibility that is not present in RDBs, which is why document-oriented databases are so popular for web applications.
After all, web applications are subject to regular changes and updates. Of course, RDBs have their advantages too, and document-oriented databases are not perfect for every situation, but let’s not digress.
Let’s move onto JSON, BSON and schemas. JSON refers to JavaScript Object Notation, but it is actually an open standard data format that can work with languages other than JavaScript.
A schema is the structure of the database, defined as tables in case of RDBs. Since document-oriented databases do not use such tables, they are essentially structure-less, or schemaless.
As for BSON, well, that stands for Binary JSON, and it’s the data storage format for the MongoDB database. That’s all you need to know about it at this stage.
Now, with the basics out the way, let’s look at why MongoDB is a good choice for making web applications:
Why go for MongoDB?
There are several reasons for the popularity of MongoDB for building web applications. MongoDB is not a perfect tool; far from it, in fact. MongoDB has several challenges, and it is not the right fit for all web applications. But MongoDB works well when it comes to web applications for the following reasons:
MongoDB is schemaless
The MongoDB database can hold collections of documents with each document having its own size, content, and number of fields. You can go back and change the key values, or add and delete them as you want to.
This also makes the structure of a single object clear and straightforward, and MongoDB is also easy to scale out when needed.
MongoDB is general-purpose
The database can be used for several web applications, including customer data management, content management, data hubs, mobile apps, Internet of Things, Big Data, product and asset catalogs and database-as-a-service.
MongoDB supports auto-sharding
Relational databases generally scale vertically, in which a single server hosts the complete database. This can limit the scale of operation, with the solution being to add horizontally and add servers rather than concentrating capacity on a single server.
Sharing of a database is done to avoid this and make hardware act as a single server. Developers have to deploy multiple relational databases across machines and develop application code for distributing the data, queries and aggregate the results.
MongoDB and other NoSQL databases support auto-sharing, which means that they automatically spread out data across various servers without the application being made aware of the composition.
MongoDB is especially useful with cloud computing. As a developer, you don’t have to build expensive and complex platforms for supporting web applications, but can focus on writing the actual application code.
A few more terms to learn about MongoDB
Alright, so we have now covered the basics and benefits of MongoDB. Before we get our hand dirty, let’s look at a few more terms that you should be familiar with:
- Database: a database contains collections, and each database has its own files on the file system. A typical MongoDB server will have several databases.
- Collection: a group of MongoDB documents is called a collection, and this is the equivalent of a table in RDBs. A single database will have a collection, and each document will have different fields. Unlike tablets, collections do not have a schema.
- Document: A document is a bunch of key-value pairs and has a dynamic schema, which means that different documents in the same collection can have different fieldsets and structures.
Building web applications
The web applications being built for this particular MongoDB guide is an RSS aggregator like Google Reader. The web applications will have two key components: A REST API and a Feed grabber.
To understand what a REST API is, you must first know a little about the MEAN stack. The code for a feed grabber, can be found even on the GitHub directory.
Understanding the MEAN stack
The MEAN stack stands for the following:
- MongoDB, which is the database to be used for the web application
- js, which is a light web application framework
- js, which is a framework for creating JavaScript and HTML5 rich web applications
- js, which is a server-side JavaScript interpreter
A REST API will be created instead of an HTML user interface for the web applications being discussed here. The Representational State Transfer (REST) API is a lighter-weight alternative to XML- based APIs. It can serve as the base for any interface type, despite not having a user interface.
REST functions on a client-server model. The client sends HTTP commands to the HTTP server, along with variable parameters encoded in the URL describing the target object of the action. The server then replies with the JSON and result code.
MongoDB and JavaScript both react well with JSON, making the MEAN stack especially suitable for the web applications.
CRUD
The acronym CRUD stands for creating, read, update and delete. These are common database operations that translate in HTTP as post, get, put and delete.
Building a REST API
Let’s begin by creating a REST API, developing the foundation for building the web applications. The application could be web-based or designed for Android, iOS or other specific platforms. To begin with, let’s list down the things that the app will be able to do:
- Allow users to create an account.
- Please enable them to subscribe or unsubscribe to feeds.
- Please give them the ability to read and mark feed entries as read or unread.
- Track RSS feeds for monitoring.
- Store user information in their respective accounts
- Track user feed subscriptions
- Track a feed entry already read by a user
Data modelling
Based on the requirements, the web applications will need four collections for managing the information:
- User collection
- Feed collection
- User-feed entry mapping collection
- Feed entry collection
Here is a closer look at each one:
Feed collection
The following JSON is a good example of modelling a feed collection:
{ "_id, ObjectId("523b1153a2aa6a3233a91412")
"requiresAuthentication": false,
"permanentlyRemoved": false,
"feedURL": "http://feeds.reuters.com/reuters/topNews",
"title": "Reuters",
"bozoBitSet": false,
"enabled": true,
"etag": "4bL78iLSZud2iXd/vd10mYC32BE",
"link": "http://www.reuters.com/ ",
"permanentRedirectURL": null,
"description": "Reuters news feed” }
The JSON document above is an RSS feed for Reuters, tracking information about the latest news published on the website. You see a lot of fields here, but the most important ones for the web applications to function is the URL of the feed and the feed description.
The URL is important for fetching content from the right source, and the description is important because it provides a summary for the feed.
The rest of the fields, meanwhile, are for internal use. You could add more or remove some of them as you feel like. Right at the top of the document is the _id field. Every document needs to have this field, and the ID must be unique.
In the above example, an ID has been created manually for the field. If you miss this out, MongoDB will automatically make one.
Tracking and collecting feed entries
If you want to track more news feeds, you can add more of them using the same format above. Once you are done adding the feeds, it is time to track and collect them. Given below is a document for feed entry collection:
{ "_id": ObjectId("523b1153a2aa6a3233a91412"),
"description": "Martin Shkreli, the poster boy for prescription drug price increases who was arrested for securities fraud this week, has stepped down from his post as chief executive officer of Turing Pharmaceuticals Inc, the company said on Friday”,
"title": "Turing Pharma names chairman to replace Shkreli as CEO",
"summary": "Turing Pharma names chairman to replace Shkreli as CEO”,
"content": [{ "base": "http://www.reuters.com/",
"type": "text/html",
"value": ”LOTS OF HTML HERE",
"language": "en" }], "published Date": ISODate("2015-12-18T18:13:58+0000"),
"link": " http://www.reuters.com/article/us-usa-crime-shkreli-ceo-idUSKBN0U122R20151218",
"feedID": ObjectId("523b1153a2aa6a3233a913f8") }
Once again, you can see the _id field filled in and some other fields such as the description, summary and title. The content field uses an array, and MongoDB allows arrays to store documents. This sub-document arrangement can be particularly useful in situations where all the information has to be held together.
Please take a note of the feedID; it has the same ObjectId type and the value of the _id as the earlier feed entry document for the Reuters feed. This offers a referential model, so you can query the feed collection on the same ID value to return the Reuters document.
Tracking the user
Here is an example document for keeping track of users:
{ "_id" : ObjectId("54ad6c3ae764de42070b27b1"),
"active" : true,
"email" : "johnhancock@example.com",
"firstName" : "John",
"lastName" : "Hancock",
"sp_api_key_id" : "6YQB0A8VXM0X8RVDPPLRHBI7J",
"sp_api_key_secret" : "veBw/YFx56Dl0bbiVEpvbjF”,
"lastLogin" : ISODate("2015-01-07T17:26:18.996Z"),
"created" : ISODate("2015-01-07T17:26:18.995Z"),
"subs" : [ ObjectId("523b1153a2aa6a3233a913f8"),
ObjectId("54b563c3a50a190b50f4d63b") ], }
Here, the user has three key attributes: first name, last name and email address. There are also two elements that can be used with the Stormpath user management API: sp_api_key_secret and sp_api_key_id.
The final field, subs, is the subscription array and tells the feed that the user is subscribed to.
Feed entry mapping
The final collection enables the mapping of users to feeds and tracking the feeds that have been read:
{ "_id" : ObjectId("523b2fcc054b1b8c579bdb82"),
"read" : true,
"user_id" : ObjectId("54ad6c3ae764de42070b27b1"),
"feed_entry_id" : ObjectId("523b1153a2aa6a3233a91412"),
"feed_id" : ObjectId("523b1153a2aa6a3233a913f8") }
As you can see, a basic true/false Boolean is used for marking whether the feed has been read or not. Now, the user should be able to perform the following functions:
- Creating an account
- Subscribing or unsubscribing to feeds
- Reading feed entries
- Marking feeds or entries as read or unread
- Reset the password
Here is a list of how to map these operations to HTTP routes and commands.
| Route | Command | Description | Variables |
| /user/enroll | POST | Register a new user | firstName lastName password |
| /user/resetPassword | PUT | Password Reset | |
| /feeds | GET | Get feed subscriptions for each user with description and unread count | |
| /feeds/subscribe | PUT | Subscribe to a news feed | feedURL |
| /feeds/entries | GET | Get all entries for feeds the user is subscribed to | |
| /feeds/<feedid>/entries | GET | Get all entries for a specific feed. | |
| /feeds/<feedid> | PUT | Mark all entries for a specific feed as read or unread | read = <true | false> |
| /feeds/<feedid>/entries/<entryid> | PUT | Mark a specific entry as either read or unread | read = <true | false> |
| /feeds/<feedid> | DELETE | Unsubscribe from this particular feed |
Secure HTTP is the standard approach used for sending sensitive details like passwords in a production environment.
Next steps: real-world authentication
User authentication is important for securely managing users, passwords and resets. There are several ways to authenticate user accounts.
For instance, you could use a Passport Plugin with Node.js, which is useful for authenticating Facebook, Twitter and social media accounts.
The above example depends on the use of Stormpath, a REST API that supports authorization and authentication via API keys and offers user management-as-a-service.
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