September 09, 2016

ReST servers in 7 languages

If you’re in the cloud, you should be building 12-factor apps. Emancipation from Enterprise IT frees you from monoliths and dogmatic language requirements. Then using microservices carves your solution into small, isolated chunks that encourage exploration.

So, if all language and frameworks are an option, how do you choose? The 12-factor app manifesto provides a pretty good scale; strong support for those tenants is a base. In addition:

  • language simplicity
  • amazing libraries
    • how much do the libraries do for you
    • do they do the right things for you
  • validation
    • is it configuration based and extensible
  • logging
    • is it done automatically by the library
    • is it easily consumed by the log aggregator
  • datastore access simplicity
  • json:api support
  • rich error responses
  • how much fun is it to work in

Not a bad list of concerns, it omits things that most already do well … but how do you eat that elephant?

What if we just started with: What does the simplest ReST server look like?


Server code

while true; do { echo -e 'HTTP/1.1 200 OK\r\n'; echo "Hello World"; } | nc -l -p 8080; done

Run Server


Although this seems a bit silly, and is difficult to extend in a meaningful way, it is pretty cool to stick in an Alpine docker container for cluster deployment testing, etc. - it’s only 4.81 MB.

GO (gorilla/mux)

Server code

package main

import (

func Index(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "Hello, World!")

func main() {
    router := mux.NewRouter().StrictSlash(true)
    router.HandleFunc("/", Index)
    http.ListenAndServe(":8080", router)

Run Server

go run

Groovy (Spark)

Download and install an SDK manager and install groovy

curl -s | bash
sdk install groovy

Server code

@Grab(group = 'com.sparkjava', module = 'spark-core', version = '2.3')
import static spark.Spark.*

get '/hello', { req, res -> 'Hello World!' }

Run server

groovy Server.groovy

Java (Spring Boot)

Server code

package hello;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;

public class HelloWorldController {

    public @ResponseBody Greeting sayHello(@RequestParam(value="name") String name) {
        return "Hello World!";
package hello;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

public class HelloWorldConfiguration {

	public static void main(String[] args) {, args);


Run server

java -jar build/libs/gs-spring-boot-0.1.0.jar


  • although the code is brief, there is significant build and configuration
  • you could use the spark framework here for a simpler implementation

JavaScript (Node/Express)

Server code

var express = require('express');
var app = express();

app.get('/', function (req, res) {
  res.send('Hello World!')

app.listen(3000, null);

Run server

node .

Python (Falcon)

Server code

import falcon
import json
class QuoteResource:
    def on_get(self, req, resp):
        resp.body = json.dumps("Hello World!")
api = falcon.API()
api.add_route('/quote', QuoteResource())

Run server

gunicorn sample:api

Ruby (Sinatra)

Server code

require 'sinatra'

get '/hi' do
  "Hello World!"

Run server

ruby hi.rb