httpdのようなもの

Main.java

import java.util.List;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.stream.Stream;
import java.net.ServerSocket;
import java.net.Socket;
import java.nio.file.Paths;
import java.nio.file.Path;
import java.nio.file.Files;
import java.nio.charset.StandardCharsets;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.IOException;
import java.io.BufferedReader;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.ZoneOffset;
import java.time.format.DateTimeFormatter;
import java.util.Locale;

public class Main {
  private static final String DOCUMENT_ROOT = "./";

  private static List<String> readLines(InputStream input)
    throws IOException {
    StringBuilder builder = new StringBuilder();
    List<String> result = new ArrayList<String>();

    for(int c; (c = input.read()) != -1; ) {
      if (c == '\r') {
        // ignore \r
      } else if (c == '\n') {
        if (builder.length() == 0) {
          break;
        } else {
          String str = builder.toString();
          result.add(str);
          builder = new StringBuilder();
        }
      } else {
        builder.append((char)c);
      }
    }

    if (builder.length() != 0) {
      result.add(builder.toString());
    }

    return result;
  }

  private static String getCurrentDateUtc() {
    return ZonedDateTime.now(ZoneOffset.UTC)
      .format(DateTimeFormatter
              .ofPattern("EEE, dd MMM yyy HH:m:ss", Locale.US))
      + " GMT";
  }

  public static Path requestedFilePath(List<String> httpRequestHeaderLines) {
    String getLine = httpRequestHeaderLines.stream()
      .filter(line -> line.startsWith("GET"))
      .findAny()
      .get();
    return Paths.get(DOCUMENT_ROOT + getLine.split(" ")[1]);
  }

  public static void writeLine(OutputStream output, String line) throws IOException {
    for(int c : (line + "\r\n").toCharArray()) {
      output.write(c);
    }
  }

  public static void sendResponseHeader(OutputStream output) throws IOException {
    List<String> headerLines = Arrays.asList("HTTP/1.1 200 OK",
                                             "Date: " + getCurrentDateUtc(),
                                             "Server: phttpd/0.1",
                                             "Connection: close",
                                             "Content-type: text/html",
                                             "");
    for(String line : headerLines) {
      writeLine(output, line);
    }
  }

  public static void sendResponseBody(OutputStream output, Path path) throws IOException {
    BufferedReader input = Files.newBufferedReader(path, StandardCharsets.UTF_8);
    for(int c; (c = input.read()) != -1; ) {
      output.write(c);
    }
  }

  public static void main(String[] args) throws Exception {
    try (ServerSocket server = new ServerSocket(8001);) {
      System.out.println("server start...");

      try (Socket socket = server.accept();) {
        System.out.println("accepted...");

        InputStream input = socket.getInputStream();
        List<String> httpRequestHeaderLines = readLines(input);
        Path path = requestedFilePath(httpRequestHeaderLines);

        System.out.println(path);

        OutputStream output = socket.getOutputStream();
        sendResponseHeader(output);
        sendResponseBody(output, path);
      } catch (IOException e) {
        e.printStackTrace();
      }

    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}