A very primitive Java web server

gistfile1.java

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.nio.CharBuffer;
import java.text.DateFormatSymbols;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;

public class WebServer
{
	public static void main(String[] args)
	{
		WebServer server = null;

		try
		{
			server = new WebServer();
		}
		catch (IOException e1)
		{
			e1.printStackTrace();
			System.exit(1);
		}

		while (true)
		{
			try
			{
				server.awaitConnection();
				if (!server.isClosed())
				{
					server.processRequest();
				}
			}
			catch (IOException e)
			{
				e.printStackTrace();
			}
			catch (InvalidRequestException e)
			{
				e.printStackTrace();
			}
			finally
			{
				try
				{
					server.closeClient();
				}
				catch (IOException e)
				{
					e.printStackTrace();
				}
			}
		}
	}
	
	private static final int START_LINE_TOKENS = 3;
	private static final String END_OF_HEADER = "";
	
	private static final String HTTP = "HTTP/1.1";
	private static final String METHOD_GET = "GET";
	private static final String ENCODING = "UTF-8";
	private static final String CONTENT_TYPE = "Content-Type: text/plain; charset=" + ENCODING;
	private static final String CONTENT_LENGTH = "Content-Length: ";
	private static final String DATE = "Date: ";
	

	private Socket clientSocket;
	private ServerSocket serverSocket;
	
	class RequestParams
	{
		public RequestParams(String method, String dir, String http)
		{
			this.method = method.toUpperCase();
			this.dir = dir.toLowerCase();
			this.http = http.toUpperCase();
		}

		public String getMethod()
		{
			return method;
		}

		public String getDir()
		{
			return dir;
		}

		public String getHttp()
		{
			return http;
		}

		String method;
		String dir;
		String http;

		public boolean validate()
		{
			return method != null && dir != null && http != null &&
					method.equals(METHOD_GET) && dir.startsWith("/") &&
					http.equals(HTTP);
		}
	}

	class InvalidRequestException extends Exception
	{}
	
	WebServer() throws IOException
	{
		serverSocket = new ServerSocket(8080);
	}

	void awaitConnection() throws IOException
	{
		clientSocket = serverSocket.accept();
	}
	
	boolean isClosed()
	{
		return clientSocket.isClosed();
	}
	
	void closeClient() throws IOException
	{
		clientSocket.close();
	}

	void closeServer() throws IOException
	{
		serverSocket.close();
	}

	private void processRequest() throws IOException, InvalidRequestException
	{
		if (clientSocket != null)
		{
			String request = readRequest();
			System.out.println(request);
			if (request.equals(""))
			{
				return; //nothing to process.
			}
			RequestParams params = parseRequest(request);
			String dir = params.getDir();
			switch (dir)
			{
				case ("/"):
				case("/latin.txt"):
					issueResponse(dir, true);
					break;
				case ("/fail"):
				default:
					issueResponse(dir, false);

			}
		}
	}
	
	private void issueResponse(String dir, boolean success) throws IOException
	{
		try (BufferedWriter buf = new BufferedWriter
				(new OutputStreamWriter(clientSocket.getOutputStream(), ENCODING)))
		{
			String statusCode = null;
			String statusResponse = null;
			String message = null;

			if (success)
			{
				statusCode = "200";
				statusResponse = "Ok";
				message = "Success!! You connected to Steve's primitive web server.\n";
			}
			else
			{
				statusCode = "404";
				statusResponse = "Not Found";
				message = "Failure, resource not found.";
			}
			
			if (success && !dir.equals("/")) message += readText(dir);
			
			long cLength = message.getBytes(ENCODING).length;
			String now = generateDate();

			buf.write(HTTP + " " + statusCode + " " + statusResponse);
			buf.write(System.lineSeparator());
			buf.write(CONTENT_TYPE);
			buf.write(System.lineSeparator());
			buf.write(CONTENT_LENGTH + cLength);
			buf.write(System.lineSeparator());
			buf.write(DATE + now);
			buf.write(System.lineSeparator());
			buf.write(System.lineSeparator());
			buf.write(message);
			buf.flush();
		}
	}
	
	private String readText(String dir)
	{
		CharBuffer buf = CharBuffer.allocate(5000);
		
		try (FileReader fr = new FileReader(dir.substring(1));)
		{
			fr.read(buf);
		}
		catch (FileNotFoundException e)
		{
			e.printStackTrace();
		}
		catch (IOException e1)
		{
			e1.printStackTrace();
		}
		
		return buf.flip().toString();
	}

	private String generateDate()
	{
		SimpleDateFormat formatter =
				new SimpleDateFormat("E, dd MMM yyyy HH:mm:ss zzz", new DateFormatSymbols(Locale.US));

		formatter.setTimeZone(TimeZone.getTimeZone("GMT"));
		return formatter.format(new Date());
	}

	private RequestParams parseRequest(String request) throws InvalidRequestException
	{
		int f = request.indexOf(System.lineSeparator());
		if (f < 0)
		{
			throw new InvalidRequestException();
		}
		String firstLine = request.substring(0, f);

		String[] tokens = firstLine.split(" ");
		if (tokens.length != START_LINE_TOKENS)
		{
			throw new InvalidRequestException();
		}
		RequestParams result = new RequestParams(tokens[0], tokens[1], tokens[2]);
		if (!result.validate())
		{
			throw new InvalidRequestException();
		}
		return result;
	}

	private String readRequest() throws IOException
	{
		String line = null;
		StringBuilder result = new StringBuilder();

		BufferedReader buf = new BufferedReader
				(new InputStreamReader(clientSocket.getInputStream()));
		
		while (true)
		{
			line = buf.readLine();
			if (line == null || line.equals(END_OF_HEADER))
				break;
			
			result.append(line);
			result.append(System.lineSeparator());
		}

		return result.toString();
	}
}