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@tomwhoiscontrary
Last active June 25, 2024 16:37
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A simple Java web server with basic logging, tracing, health check, graceful shutdown and zero dependencies
import com.sun.net.httpserver.Filter;
import com.sun.net.httpserver.HttpExchange;
import com.sun.net.httpserver.HttpHandler;
import com.sun.net.httpserver.HttpServer;
import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.InetSocketAddress;
import java.util.Arrays;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.function.Supplier;
import java.util.logging.Logger;
public class Main {
public static final String REQUEST_ID_KEY = "requestId";
public static void main(String[] args) throws IOException, InterruptedException {
InetSocketAddress listenAddr = args.length > 0
? new InetSocketAddress(args[0].split(":")[0], Integer.parseInt(args[0].split(":")[1]))
: new InetSocketAddress(5000);
Logger logger = Logger.getLogger("http");
logger.info("Server is starting...");
AtomicBoolean healthy = new AtomicBoolean(true);
Supplier<String> nextRequestId = () -> Long.toString(System.nanoTime());
HttpServer server = HttpServer.create(listenAddr, 0);
List<Filter> filters = Arrays.asList(tracing(nextRequestId), logging(logger));
server.createContext("/", index()).getFilters().addAll(filters);
server.createContext("/healthz", healthz(healthy)).getFilters().addAll(filters);
ExecutorService executor = Executors.newCachedThreadPool();
server.setExecutor(executor);
Runtime.getRuntime().addShutdownHook(new Thread(() -> {
logger.info("Server is shutting down...");
healthy.set(false);
server.stop(5);
logger.info("Server stopped");
}));
logger.info("Server is ready to handle requests at " + listenAddr);
healthy.set(true);
server.start();
}
private static HttpHandler index() {
return http -> {
if (!http.getRequestURI().getPath().equals("/")) {
http.sendResponseHeaders(HttpURLConnection.HTTP_NOT_FOUND, -1);
return;
}
http.getResponseHeaders().add("Content-Type", "text/plain; charset=utf-8");
http.getResponseHeaders().add("X-Content-Type-Options", "nosniff");
http.sendResponseHeaders(HttpURLConnection.HTTP_OK, 0);
http.getResponseBody().write("Hello, World!\n".getBytes());
http.close();
};
}
private static HttpHandler healthz(AtomicBoolean healthy) {
return http -> {
if (healthy.get()) http.sendResponseHeaders(HttpURLConnection.HTTP_NO_CONTENT, -1);
else http.sendResponseHeaders(HttpURLConnection.HTTP_UNAVAILABLE, -1);
};
}
private static Filter logging(Logger logger) {
return new Filter() {
@Override
public void doFilter(HttpExchange http, Chain chain) throws IOException {
try {
chain.doFilter(http);
} finally {
Object possibleRequestId = http.getAttribute(REQUEST_ID_KEY);
String requestId = possibleRequestId instanceof String ? (String) possibleRequestId : "unknown";
logger.info(String.format("%s %s %s %s %s",
requestId,
http.getRequestMethod(),
http.getRequestURI().getPath(),
http.getRemoteAddress(),
http.getRequestHeaders().getFirst("User-Agent")));
}
}
@Override
public String description() {
return "logging";
}
};
}
private static Filter tracing(Supplier<String> nextRequestId) {
return new Filter() {
@Override
public void doFilter(HttpExchange http, Chain chain) throws IOException {
String requestId = http.getRequestHeaders().getFirst("X-Request-Id");
if (requestId == null) requestId = nextRequestId.get();
http.setAttribute(REQUEST_ID_KEY, requestId);
http.getResponseHeaders().add("X-Request-Id", requestId);
chain.doFilter(http);
}
@Override
public String description() {
return "tracing";
}
};
}
}
@GavinRay97
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Awesome, thank you!

I didn't know about the HttpURLConnection header enum, I was looking for something like this when writing a basic server implementation!

@tomwhoiscontrary
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@GavinRay97 It is a useful little trick! Just a shame there isn't anything similar for common header names, MIME types, etc.

@alexec
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alexec commented Nov 22, 2023

nice work

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