Backend Overview

Static web server

Return only the contents of files

CGI Protocol

Common Gateway Interface - run a program to generate a response

Application Server

Language/Platform specific http implementations

• CGI - PHP
• webContainer - Java
• USAPI - dotNet
• uWSGI - Python
• libUV - node.js

Serverless

CLEAN application structure

CLEAN application structure

• Use-cases encapsulate Domain/Business logic
• Use-cases have input & output interfaces
• Controllers initiate use-cases
• Presenters observe use-case results

http server in node.js

          /* server.js */
          var http = require('http'),
              server = http.createServer(function (req, res) {
                  //server executes callback on every connection
                  res.send('Hello Web!');
          });

          //start the server on port 8080
          server.listen(8080);
          

      node server.js
  

Routing

1. Parse the URL
2. Select the most appropriate response strategy
3. Execute it with on the request parameters

Express for Node.js

    //create new tasks
     srv.post('/task', (req, res) => {
       task = tasks.createTask(req.params);
       res.json(task);
     });

     //get an existing task
     srv.get('/task/:id', (req, res) => {
       res.json(tasks.get(req.params.id));
     });

     //toggle task done
     srv.put('/task/:id/toggle', (req, res) => {
       const task = tasks.get(req.params.id);
       task.done = !task.done;
       res.json(task);
     });
  

Flask for Python

    @app.route('/')
    def show_entries():
      db_cursor = db.execute('SELECT title, text FROM entries')
      entries = db_cursor.fetchall()
      return render_template('show_entries.html', entries=entries)

    @app.route('/add', methods=['POST'])
    def add_entry():
      if not session.get('logged_in'):
        abort(401)
      db.execute('INSERT INTO entries (title, text) VALUES (?, ?)',
                      [request.form['title'], request.form['text']])
      db.commit()
      flash('New entry was successfully posted')
      return redirect(url_for('show_entries'))
  

Vert.x for Java

      public static void main(String[] args) {
        Router router = Router.router(vertx);

        router.get("/products").handler(this::handleListProducts);

        vertx.createHttpServer()
          .requestHandler(router::accept)
          .listen(8080);
      }

      private void handleListProducts(RoutingContext routingContext) {
        JsonArray results = new JsonArray();

        products.forEach((k, v) -> results.add(v));

        routingContext.response()
          .putHeader("content-type", "application/json")
          .end(results.encodePrettily());
      }
    

Security

• System take-ove (rootkit)
• Code execution (SQL injection)
• Data leak / loss (Ransomware)
• Malicious communication (CSRF, DDOS)

Links

• Flask for Pythons
• Express for NodeJS
• Rails for Ruby
• ASP.NET for C#
• Vert.x for Java

Course Schedule: