Web Apps and Services

Motivating Network Communication

  • Servers communicate with each other by sending packets
  • These packets follow a network-layer protocol

  • A few network-layer protocols include:

    • IP
    • TCP
  • There are data chunks within those packets
  • These data chunks follow an application-layer protocol

  • A few application-layer protocols include:

    • SOAP
    • HTTP
    • HTTPS
    • FTP
    • SMTP

Defining a Web and REST API

  • An API is a set of methods
  • It is used for communicating with other software components
  • An API with methods following an application-layer protocol is referred to as a web API

  • A web API that satisfies the following is considered a REST API:

    • Resources are unambiguously requested via URIs
    • HATEOUS
  • Hypermedia as the engine of application state is abbreviated as HATEOUS
  • HATEOUS is satisfied if transitions and actions are clearly exposed to the client by the server via hyperlinks and hypertext

Defining a Web Service

  • Generally, a web service doesn't need a user interface
  • A web service operates over HTTP
  • A web service refers to software
  • This software is in the form of an API
  • This API can be designed as a REST or SOAP API
  • A web service serves data in any format
  • This includes data formatted as XML, JSON, etc.

  • The following frameworks can be used to build web APIs:

    • Node.js
    • Flask
    • Spring Boot
  • In other words, these frameworks can be used to build webservices

Defining a Web Application

  • Generally, a web application involves a user interface
  • A web application operates over HTTP
  • A web application refers to software

  • This software is in the form of the following:

    • HTML
    • CSS
    • JavaScript

  • In other words, the following properties are listed below:

    • Web Service: Runs on the server
    • Web Application: Runs as the client

Separating the Front-End and Back-End

  • Typically, the frontend and backend refer to different networks

  • The frontend does the following:

    • Sends HTTP-formatted requests to the backend
    • Interprets HTTP-formatted responses
    • Extracts the JSON-formatted data if successful

  • The backend does the following:

    • Interprets HTTP-formatted requests

    • Sends HTTP-formatted responses to the frontend

      • These contain a response code and JSON-formatted data

Defining a Microservice

  • A microservice is a software architecture
  • It is based on using web services
  • This architecture simplifies big applications by splitting them into smaller applications
  • Each smaller application serves an individual purpose
  • These smaller applications are web services
  • This architecture allows a web service to use other web services easily

  • By doing this, we can:

    • Build new web services linked to old web services
    • Remove rdundancies from building many large applications
  • The word micro in microservices emphasises the idea of how they're based on making web services as small as possible

Examples of Web Services

  • The Yahoo Weather API
  • The Google Maps API
  • The Facebook Marketing API
  • Spotify API

Describing Stateless Applications

  • Statelessness is a property of a web service
  • A stateless application doesn't store any information from a client request
  • Meaning, Sessions and Cookies should be avoided
  • Typically, web services should try to be stateless
  • However, certain webservices are inherently stateful
  • For example, a shopping cart is a stateful feature by design
  • Therefore, a web application implementing a shopping cart should be stateful

References

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Web Servers

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