Demystifying REST: Understanding the Basics and Key Concepts

REST Introduction and REST Architecture

• Definition of REST:

  • REST stands for Representational State Transfer.

  • Understanding each term:

    • State: Represents data.

    • Representational: Denotes a data format (e.g., XML, JSON, YAML, HTML, plain text).

    • Transfer: Involves transferring data between consumer and provider using HTTP protocol.

• REST Architecture Overview:

  • Involves a client-server model where a client sends HTTP requests to a server, and the server processes and responds.

  • Clients can be diverse (e.g., Android, iOS, desktop, web applications).

  • Independence: Client and server should be independent; changes in one shouldn't affect the other.

  • Message Exchange Format: Data exchanged between client and server typically in JSON or XML.

• Key Points about REST:

  • Origin: Coined by Roy Fielding, inventor of HTTP protocol.

  • Purpose: Facilitates communication between applications over HTTP, akin to browser-server interaction.

  • Popularity: Rapid adoption due to increased mobile device usage, allowing web and mobile clients to consume the same APIs.

• REST Architectural Constraints:

  • Client-Server Architecture: Client and server are distinct, independent components.

  • Statelessness: No session data stored on the server; each request is stateless.

  • Cacheability: Clients can cache responses for improved performance.

  • Uniform Interface: Provides a consistent, generic interface for interactions, simplifying architecture.

  • Layered System: Servers can have multiple layers for scalability and load balancing.

  • Code on Demand (Optional): Allows clients to download and execute code from the server, though rarely used.

• Conclusion:

  • RESTful APIs follow these architectural constraints to ensure effective communication between clients and servers.

Key Terms:

• REST

• Representational State Transfer

• State

• Representational

• Transfer

• HTTP protocol

• Client

• Server

• Web services

• HTTP request

• HTTP response

• Message Exchange Format

• JSON

• XML

• Roy Fielding

• Client-server architecture

• Independence

• Statelessness

• Cacheability

• Uniform Interface

• Layered System

• Code on Demand

REST Key Concepts - Resource, URI and Sub-resource

Notes on REST Key Concepts:

• Resource in REST:

  • In a REST-based system, everything is a resource.

  • A resource is anything exposed to the outside world through the application.

  • Examples of resources in various systems: Employee, Department, Address, Project, Task (Employee Management System); Student, Teacher, Class, Subject, School (Student Management System); Post, Comment, User, Tags, Category (Blog Application).

  • CRUD (Create, Read, Update, Delete) REST APIs are typically created for each resource.

  • Clients consume these REST APIs to perform actions on resources.

• Uniform Resource Identifier (URI):

  • URI is used to identify resources.

  • Each URI should be unique.

  • Examples of URIs for CRUD operations on a Post resource:

    • URL to list posts

    • URL to retrieve a post by ID

    • URL to create a new post

    • URL to update a post

    • URL to delete a post

• Sub-resource:

  • Sub-resources are used to model relationships in REST APIs.

  • Relationships are modeled by placing a sub-resource after a resource.

  • Pattern: resource/resource-id/sub-resource/sub-resource-id.

  • Example: In a blog application, posts can have comments as sub-resources. To retrieve comments for a particular post, the URI would be post/post-id/comments.

  • Sub-resources are used when child objects cannot exist without their parent (e.g., comments cannot exist without a post, drivers cannot exist without a car).

  • Deleting the parent resource may also delete the associated sub-resources.

Key Terms:

• Resource

• CRUD

• Uniform Resource Identifier (URI)

• Sub-resource

• Relationships

• Parent-child relationship

• HTTP Methods

• HTTP Status Codes

REST Key Concepts - Http Methods

Notes on HTTP Methods in RESTful Web Services:

• HTTP Methods:

  • GET: Used to retrieve or get a collection or a single resource. Not for modifying or creating resources.

  • POST: Utilized to create a new resource. Typically used for adding new entities like employees, students, or users.

  • PUT: Employed to update an existing resource. Used when modifying existing entities such as updating employee details or student information.

  • DELETE: Used to delete a collection or a single resource. Enables removal of entities like students or specific records identified by their unique identifiers.

  • PATCH: Optionally used to partially update an existing resource.

• Usage Examples:

  • GET Method: Retrieve a list of posts or a single post by ID.

  • POST Method: Create a new post in a blog application.

  • PUT Method: Update an existing post by specifying its ID.

  • DELETE Method: Delete a post or other resources by their IDs.

• Additional Note:

  • PATCH Method: Used for partial updates to existing resources, updating specific fields without modifying the entire resource.

Key Terms:

• HTTP Methods

• GET

• POST

• PUT

• DELETE

• PATCH

• RESTful Web Services

• Resource Modification

• Resource Creation

• Resource Deletion

• Postman

REST Key Concepts - HTTP Status Codes

Notes on Important HTTP Status Codes:

• Overview:

  • HTTP status codes indicate the outcome of a request made by a client to a server.

  • These status codes help in understanding the status of the request and guide further actions.

• 200 OK:

  • Indicates: Request is successful, and response content is returned to the client as appropriate.

  • Example: Retrieving a collection of blog posts or a single post.

• 201 CREATED:

  • Indicates: Request is successful, and a new resource is created.

  • Example: Creating a new blog post; server responds with the newly created resource.

• 400 Bad Request:

  • Indicates: Server failed to process the request due to malformed syntax in the request.

  • Example: Client passed invalid parameters; server responds with a bad request status code.

• 401 Unauthorized:

  • Indicates: Authentication is required for the resource, and the client needs to provide appropriate credentials.

  • Example: Accessing a protected resource without valid authentication; server responds with an unauthorized status code.

• 403 Forbidden:

  • Indicates: Server refuses to respond to the request, even if the request is valid.

  • Example: Attempting to access unauthorized resources; server responds with a forbidden status code.

• 404 Not Found:

  • Indicates: Requested resource is not found at the specified location.

  • Example: Attempting to delete a blog post that does not exist; server responds with a not found status code.

• 500 Internal Server Error:

  • Indicates: An unexpected error occurred on the server, and the request cannot be fulfilled.

  • Example: Server-side error during user authentication or other processing; server responds with an internal server error status code.

Key Terms:

• HTTP Status Codes

• 200 OK

• 201 CREATED

• 400 Bad Request

• 401 Unauthorized

• 403 Forbidden

• 404 Not Found

• 500 Internal Server Error

• Client-Server Communication