RESTful API

What is RESTful API?

• Representational

• State

• Transfer

1. One form of Software Architecture for Hypermedia systems such as the WWW (World Wide Web)

2. A REST Server allows clients to access and modify server information using the HTTP Protocol

3. Information is provided in text, xml, json formats

   • Nowadays json is the mainstream!

HTTP method

4 commonly used methods in REST-based architecture

1. GET

   : Retrieve

2. PUT

   : Create and update

3. DELETE

   : Remove

4. POST

   : Create

Creating a Database

• Create a JSON-based user database

Test04_RESTful > data > user.json

{
    "first_user": {
        "password": "first_pass",
        "name": "chloe"
    },
    "second_user":{
        "password": "second_pass",
        "name": "bella"
    }
}

1. API: GET/list

• Create a GET API that outputs all user lists

router > main.js

module.exports = function(app,fs){

    app.get('/', function(request, response) {
        response.render('index', {
            title: "MY HOMEPAGE",
            length: 5
        })
    });
    app.get('/list', function(request, response){
        fs.readFile(__dirname + "../data/" + "user.json", "utf8", function(error, data){

            console.log(data);
            response.end(data);
        })
    })
}

• __dirname

  • Represents the location of the current module

  • Since the router module is inside the router folder, you need to use a relative path to access the data folder!

After running the server, access http://localhost/list

image-20200407040640515

2. API: GET/getUser/:username

• Create a GET API that retrieves detailed information for a specific username!

Add to router > main.js

   app.get('/getUser/:username', function(req, res){
       fs.readFile( __dirname + "/../data/user.json", 'utf8', function (err, data) {
            var users = JSON.parse(data);
            res.json(users[req.params.username]);
       });
    });

• After reading the file, it finds and outputs the user id

  • If the user is found, it outputs the user data

  • If not found, it outputs {}

• Since reading a file with fs.readFile() returns the data in text format, you need to use JSON.parse()!

After restarting the server, access http://localhost/getUser/first_user

image-20200407041513712

3. API: POST addUser/:username

body: { "password": "", "name": "" }

Add to router > main.js

app.post('/addUser/:username', function(req, res){

        var result = {  };
        var username = req.params.username;

        // CHECK REQ VALIDITY
        if(!req.body["password"] || !req.body["name"]){
            result["success"] = 0;
            result["error"] = "invalid request";
            res.json(result);
            return;
        }

        // LOAD DATA & CHECK DUPLICATION
        fs.readFile( __dirname + "/../data/user.json", 'utf8',  function(err, data){
            var users = JSON.parse(data);
            if(users[username]){
                // DUPLICATION FOUND
                result["success"] = 0;
                result["error"] = "duplicate";
                res.json(result);
                return;
            }

            // ADD TO DATA
            users[username] = req.body;

            // SAVE DATA
            fs.writeFile(__dirname + "/../data/user.json",
                         JSON.stringify(users, null, '\t'), "utf8", function(err, data){
                result = {"success": 1};
                res.json(result);
            })
        })
    });

• Returns an error if the JSON format is Invalid

• If valid, opens the file, checks for username duplication, then adds to the JSON data and saves again

• stringify(users, null, 2) is for JSON pretty-print

4. API: PUT updateUser/:username

body: { "password": "", "name": "" }

• An API that updates user information

• Uses the PUT method

  • An idempotent PUT API

    • Must guarantee the same result no matter how many times the request is made!

Add to router > main.js

app.put('/updateUser/:username', function(req, res){

        var result = {  };
        var username = req.params.username;

        // CHECK REQ VALIDITY
        if(!req.body["password"] || !req.body["name"]){
            result["success"] = 0;
            result["error"] = "invalid request";
            res.json(result);
            return;
        }

        // LOAD DATA
        fs.readFile( __dirname + "/../data/user.json", 'utf8',  function(err, data){
            var users = JSON.parse(data);
            // ADD/MODIFY DATA
            users[username] = req.body;

            // SAVE DATA
            fs.writeFile(__dirname + "/../data/user.json",
                         JSON.stringify(users, null, '\t'), "utf8", function(err, data){
                result = {"success": 1};
                res.json(result);
            })
        })
    });

5. API: DELETE deleteUser/:username

• An API that deletes user data

  • Uses the DELETE method

Add to router > main.js

app.delete('/deleteUser/:username', function(req, res){
        var result = { };
        //LOAD DATA
        fs.readFile(__dirname + "/../data/user.json", "utf8", function(err, data){
            var users = JSON.parse(data);

            // IF NOT FOUND
            if(!users[req.params.username]){
                result["success"] = 0;
                result["error"] = "not found";
                res.json(result);
                return;
            }

            // DELETE FROM DATA
            delete users[req.params.username];

            // SAVE FILE
            fs.writeFile(__dirname + "/../data/user.json",
                         JSON.stringify(users, null, '\t'), "utf8", function(err, data){
                result["success"] = 1;
                res.json(result);
                return;
            })
        })

    });