HttpServerHelloWorld.java

package httpserverhelloworld;

import java.io.*;
import java.net.InetSocketAddress;

import com.google.gson.Gson;
import com.sun.net.httpserver.HttpExchange;
import com.sun.net.httpserver.HttpHandler;
import com.sun.net.httpserver.HttpServer;

public class HttpServerHelloWorld {
    public static void main(final String[] args) throws Exception {
        final HttpServer server = HttpServer.create(new InetSocketAddress(8000), 0);
        server.createContext("/test", new MyHandler().setSomeValue(123));
        server.createContext("/hello", new MyHandler().setSomeValue(321));
        server.createContext("/add", new AddHandler());
        CountHandler countHandler = new CountHandler();
        server.createContext("/count", countHandler);
        server.createContext("/count-copy", countHandler);
        server.createContext("/count-by-2", new CountHandler().setStepSize(2));

        server.setExecutor(null);  // creates a default executor

        server.start();
    }

    private static class CountHandler implements HttpHandler {
        private int stepSize = 1;
        public CountHandler setStepSize(int x) { stepSize = x; return this; }

        private int count = -1;

        public void handle(HttpExchange t) throws IOException {
            count += stepSize;

            String response = "" + count + "\n";

            t.sendResponseHeaders(200, response.length());
            final OutputStream os = t.getResponseBody();
            os.write(response.getBytes());
            os.close();
        }
    }

    static class MyHandler implements HttpHandler {
        private int someValue = 1;
        public MyHandler setSomeValue(int x) { this.someValue = x; return this; }
        public int getSomeValue() { return someValue; }

        @Override
        public void handle(final HttpExchange t) throws IOException {
            String response;
            if (t.getRequestMethod().equals("DELETE")) {
                if (this.someValue < 200) {
                    response = "it's gone now..." + this.someValue;
                } else {
                    response = "too valuable: " + this.someValue + "\n";
                }
            } else {
                response = "this is the response: " + t.getRequestMethod() + "\n";
            }
            // 200 == HTTP OK
            t.sendResponseHeaders(200, response.length());
            final OutputStream os = t.getResponseBody();
            os.write(response.getBytes());
            os.close();
        }
    }

    static class AddHandler implements HttpHandler {
        @Override
        public void handle(HttpExchange t) throws IOException {
            System.out.println("handling");
            InputStream requestBody = t.getRequestBody();
            BufferedReader br = new BufferedReader(new InputStreamReader(requestBody));

            String data = "{\"a\": 5, \"b\": 7}";

            Gson gson = new Gson();
            AddingRoot adding = gson.fromJson(data, AddingRoot.class);

            ResponseRoot responseRoot = new ResponseRoot();
            responseRoot.setC(adding.getA() + adding.getB());

            String responseJson = gson.toJson(responseRoot);
            System.out.println(responseJson);

            t.sendResponseHeaders(200, responseJson.length());

            final OutputStream os = t.getResponseBody();
            os.write(responseJson.getBytes());
            os.close();
        }
    }

    static class AddingRoot {
        private int a, b;
        public int getA() { return a; }
        public int getB() { return b; }
    }

    static class ResponseRoot {
        private int c;
        public int getC() { return c; }
        public void setC(int c) { this.c = c; }
    }
}