java-http/Main.java

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;

public class Main {

	public static void main(String[] args) throws Exception {
		try (ServerSocket serverSocket = new ServerSocket(8080)) {
			System.out.println("listening on socket 8080...");
			while (true) {
				// .accept() blocks until we have a client
				try (Socket client = serverSocket.accept()) {
					handleClient(client);
				}
			}
		}
	}

	public static void handleClient(Socket client) throws IOException {

		System.out.println("Debug: got new client" + client.toString());
		BufferedReader br = new BufferedReader(new InputStreamReader(client.getInputStream()));

		StringBuilder requestBuilder = new StringBuilder();
		String line;
		while (!(line = br.readLine()).isBlank()) {
			requestBuilder.append(line + "\r\n");
		}
		String request = requestBuilder.toString();
		// System.out.println(request);
		// PARSE THE REQUEST
		String[] requestLines = request.split("\r\n");
		String[] requestLine = requestLines[0].split(" ");
		String method = requestLine[0];
		String path = requestLine[1];
		String version = requestLine[2];
		String host = requestLines[1].split(" ")[1];

		List<String> headers = new ArrayList<>();
		// we start the loop from 2 because 0 is GET / HTTP/1.1 and 1 is the host
		for (int h = 2; h < requestLines.length; h++) {
			String header = requestLines[h];
			headers.add(header);
		}

		String accessLog = String.format("Client %s, method %s, path %s, version %s, host %s, headers %s",
				client.toString(),
				method, path, version, host, headers.toString());
		System.out.println(accessLog);

		Path filepath = getFilePath(path);
		if (Files.exists(filepath)) {
			// file exist
			String contentType = guessContentType(filepath);
			sendResponse(client, "200 OK", contentType, Files.readAllBytes(filepath));
		} else {
			// 404
			byte[] notFoundContent = "<h1>404 Something went wrong</h1>".getBytes();
			sendResponse(client, "404 Not Found", "text/html", notFoundContent);
		}

	}

	private static void sendResponse(Socket client, String status, String contentType, byte[] content)
			throws IOException {
		OutputStream clientOutput = client.getOutputStream();
		clientOutput.write("HTTP/1.1 200 OK\r\n".getBytes());
		clientOutput.write("ContentType: text/html\r\n".getBytes());
		clientOutput.write("\r\n".getBytes());
		clientOutput.write(content);
		// These (windows) newlines indicate that the response is over
		clientOutput.write("\r\n\r\n".getBytes());
		clientOutput.flush();
		client.close();
	}

	private static String guessContentType(Path filepath) throws IOException {
		return Files.probeContentType(filepath);
	}

	private static Path getFilePath(String path) {
		if ("/".equals(path)) {
			path = "/index.html";
		}
		return Paths.get("/home/andrzej/dev/java-http", path);
	}

}