1. Introduction to concepts

1. REST concepts

REST: (Representational State Transfer) Representational State Transfer, which defines a common access format for resources, is a style of design and development for network applications.

Conceptually, you need to understand the following names:

1. Resource s

That is, anything you get on the server, a user record, a user's password, a picture, and so on.

1. Representation of resources

That is, the resource format, which is HTML, XML, JSON, plain text, pictures, and so on, can express the resources you get in a variety of formats.

1. State Transfer

That is, URL s locate resources and describe operations with HTTP verbs (GET,POST,DELETE,DETC).Operations are verbs and resources are nouns.

1. Uniform Interface

That is, resources are operated on through a unified interface.

2. REST features

REST is typically based on existing, widely popular protocols and standards that use HTTP, URI s, and XML as well as HTML, each representing a resource.

REST usually uses JSON data format.

Four approaches to the basic REST architecture:

• GET - Used to get data
• PUT - For updating or adding data
• DELETE - Used to delete data
• POST - For adding data

A scenario is presented below.

3. REST Advantages

• Cache can be used more efficiently to improve response speed
• Statelessness of communication itself allows different servers to handle different requests in a series of requests, which improves server scalability
• Browsers act as clients to simplify software requirements
• REST has less software dependency than other mechanisms that overlay the HTTP protocol
• No additional resource discovery mechanism is required
• Better long-term compatibility in software technology evolution

2. Introduction of Examples

REST defines a common access format for resources, and the next consumer example describes the RESTful API definition:

1. Get all user s

GET /api/user

1. Gets the user of the specified id

GET /api/user/100

1. Create a new user record

POST /api/user

1. Update a user record

PUT /api/user/100

1. Delete a user record

DELETE /api/user/100

1. Get all the expense bills for a user

GET  /api/user/100/bill

1. Get a user's bills for consumption at a specified time

GET  /api/user/100/bill?from=201910&to=201911

The RESTful style API above contains almost common business situations.

3. Nodejs Implements RESTful API

1. Initialize mock data

This case demonstrates using mock data as follows:

{
   "user1" : {
      "name" : "leo",
      "password" : "123456",
      "profession" : "teacher",
      "id": 1
   },
   "user2" : {
      "name" : "pingan8787",
      "password" : "654321",
      "profession" : "librarian",
      "id": 2
   },
   "user3" : {
      "name" : "robin",
      "password" : "888888",
      "profession" : "clerk",
      "id": 3
   }
}

We will implement the following RESTful API:

2. Get a list of users

In this step, we will create listUsers in the RESTful API to read a list of users'information:

// index.js
const express = require('express');
const app = express();
const fs = require("fs");

// Define an interface for reading the user's information list
app.get('/listUsers', (req, res) => {
   fs.readFile( __dirname + "/" + "users.json", 'utf8', (err, data) => {
       console.log( data );
       res.end( data );
   });
})

const server = app.listen(8081, function () {
    const {address, port} = server.address();
    console.log("server run in: http://%s:%s", address, port);
})

3. Add Users

In this step, we will create an addUser in the RESTful API to add user records:

// index.js
// Omitting the previous file only shows the interfaces that need to be implemented

// mock A new piece of data to add
const user = {
   "user4" : {
      "name" : "pingan",
      "password" : "password4",
      "profession" : "teacher",
      "id": 4
   }
}

// Define an interface for adding user records
app.get('/addUser', (req, res) => {
   // Read existing data
   fs.readFile( __dirname + "/" + "users.json", 'utf8', (err, data) => {
       data = JSON.parse( data );
       data["user4"] = user["user4"];
       console.log( data );
       res.end( JSON.stringify(data));
   });
})

4. Get user details

In this step, we append: id to the URI in the RESTful API to get specific user details:

// index.js
// Omitting the previous file only shows the interfaces that need to be implemented

// Define an interface to get specific user details
app.get('/:id', (req, res) => {
   // First we read existing users
   fs.readFile( __dirname + "/" + "users.json", 'utf8', (err, data) => {
       data = JSON.parse( data );
       var user = data["user" + req.params.id] 
       console.log( user );
       res.end( JSON.stringify(user));
   });
})

5. Delete the specified user

In this step, we will create a deleteUser in the RESTful API to delete the specified user:

// index.js
// Omitting the previous file only shows the interfaces that need to be implemented

// mock A user id to delete
const id = 2;

app.get('/deleteUser', (req, res) => {
   fs.readFile( __dirname + "/" + "users.json", 'utf8', (err, data) => {
       data = JSON.parse( data );
       delete data["user" + id];
       console.log( data );
       res.end( JSON.stringify(data));
   });
})

Reference material

1. Wikipedia-Presentation State Transition
2. RESTful Style Spring MVC
3. <Node.js RESTful API>

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