Server.java

import com.sun.net.httpserver.*;

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

public class Server {

	public static void main(String[] args) throws IOException {
		if (args.length < 2 || args[0].equals("-help") || args[0].equals("--help")) {
			System.out.println("Usage: java Server.java $web_root $port");
			return;
		}
	    HttpServer httpServer = HttpServer.create();
		String pathToRoot = args[0].endsWith("/") ? args[0] : args[0] + "/";

        File base = new File(pathToRoot);
        if (! base.exists() || ! base.isDirectory())
            throw new IllegalStateException("Couldn't find webroot: "+pathToRoot);
	    httpServer.createContext("/", ex -> handle(pathToRoot, ex));
	    int port = Integer.parseInt(args[1]);
	    httpServer.bind(new InetSocketAddress("localhost", port), 100);
	    httpServer.start();
	}

	public static void handle(String pathToRoot, HttpExchange httpExchange) throws IOException {
		String path = httpExchange.getRequestURI().getPath();
		try {
			path = path.substring(1);
			path = path.replaceAll("//", "/");
			if (path.length() == 0)
				path = "index.html";

			File file = new File(pathToRoot + path);
			InputStream in = new FileInputStream(file);
			if (in == null) {
				String toAsset = pathToRoot + path + ".html";
				file = new File(toAsset);
			}

			if (path.endsWith(".js"))
				httpExchange.getResponseHeaders().set("Content-Type", "text/javascript");
			else if (path.endsWith(".html"))
				httpExchange.getResponseHeaders().set("Content-Type", "text/html");
			else if (path.endsWith(".css"))
				httpExchange.getResponseHeaders().set("Content-Type", "text/css");
			else if (path.endsWith(".json"))
				httpExchange.getResponseHeaders().set("Content-Type", "application/json");
			else if (path.endsWith(".svg"))
				httpExchange.getResponseHeaders().set("Content-Type", "image/svg+xml");
			if (httpExchange.getRequestMethod().equals("HEAD")) {
				httpExchange.getResponseHeaders().set("Content-Length", "" + file.length());
				httpExchange.sendResponseHeaders(200, -1);
				return;
			}

			httpExchange.sendResponseHeaders(200, file.length());
			OutputStream body = httpExchange.getResponseBody();
			byte[] tmp = new byte[4096];
			int r;
			while ((r=in.read(tmp)) >= 0)
				body.write(tmp, 0, r);
			body.flush();
			body.close();
		} catch (FileNotFoundException t) {
			System.err.println("Error retrieving: " + path);
			t.printStackTrace();
			httpExchange.sendResponseHeaders(404, 0);
			httpExchange.getResponseBody().close();
		} catch (Throwable t) {
			System.err.println("Error retrieving: " + path);
			t.printStackTrace();
		}
	}
}