How would you implement a simple HTTP server (not just a client) using the lightweight com.sun.net.httpserver.HttpServer class bundled with the JDK, without a full framework like Spring?

com.sun.net.httpserver.HttpServer (available in the JDK itself, though technically part of an internal/unsupported-officially package historically, now more formally exposed) provides a minimal, dependency-free way to stand up a basic HTTP server for simple use cases (a local development mock server, a lightweight health-check endpoint, a simple internal admin tool) without pulling in a full web framework, by registering a HttpHandler for specific URL paths that receives the raw HttpExchange (giving access to the request and letting you write the response) -- while genuinely useful for its simplicity in narrow scenarios, it lacks the routing, middleware, and ecosystem support a full framework like Spring Boot or Javalin provides, making it unsuitable for anything beyond simple, low-traffic, internal-use cases.

HttpServer server = HttpServer.create(new InetSocketAddress(8080), 0);
server.createContext("/health", exchange -> {
    String response = "OK";
    exchange.sendResponseHeaders(200, response.length());
    try (OutputStream os = exchange.getResponseBody()) {
        os.write(response.getBytes());
    }
});
server.setExecutor(Executors.newFixedThreadPool(4));
server.start();