Simple HTTP Web Server made in Java for a tutorial on the SSaurel's Blog

JavaHTTPServer.java

import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Date;
import java.util.StringTokenizer;

// The tutorial can be found just here on the SSaurel's Blog : 
// https://www.ssaurel.com/blog/create-a-simple-http-web-server-in-java
// Each Client Connection will be managed in a dedicated Thread
public class JavaHTTPServer implements Runnable{ 
	
	static final File WEB_ROOT = new File(".");
	static final String DEFAULT_FILE = "index.html";
	static final String FILE_NOT_FOUND = "404.html";
	static final String METHOD_NOT_SUPPORTED = "not_supported.html";
	// port to listen connection
	static final int PORT = 8080;
	
	// verbose mode
	static final boolean verbose = true;
	
	// Client Connection via Socket Class
	private Socket connect;
	
	public JavaHTTPServer(Socket c) {
		connect = c;
	}
	
	public static void main(String[] args) {
		try {
			ServerSocket serverConnect = new ServerSocket(PORT);
			System.out.println("Server started.\nListening for connections on port : " + PORT + " ...\n");
			
			// we listen until user halts server execution
			while (true) {
				JavaHTTPServer myServer = new JavaHTTPServer(serverConnect.accept());
				
				if (verbose) {
					System.out.println("Connecton opened. (" + new Date() + ")");
				}
				
				// create dedicated thread to manage the client connection
				Thread thread = new Thread(myServer);
				thread.start();
			}
			
		} catch (IOException e) {
			System.err.println("Server Connection error : " + e.getMessage());
		}
	}

	@Override
	public void run() {
		// we manage our particular client connection
		BufferedReader in = null; PrintWriter out = null; BufferedOutputStream dataOut = null;
		String fileRequested = null;
		
		try {
			// we read characters from the client via input stream on the socket
			in = new BufferedReader(new InputStreamReader(connect.getInputStream()));
			// we get character output stream to client (for headers)
			out = new PrintWriter(connect.getOutputStream());
			// get binary output stream to client (for requested data)
			dataOut = new BufferedOutputStream(connect.getOutputStream());
			
			// get first line of the request from the client
			String input = in.readLine();
			// we parse the request with a string tokenizer
			StringTokenizer parse = new StringTokenizer(input);
			String method = parse.nextToken().toUpperCase(); // we get the HTTP method of the client
			// we get file requested
			fileRequested = parse.nextToken().toLowerCase();
			
			// we support only GET and HEAD methods, we check
			if (!method.equals("GET")  &&  !method.equals("HEAD")) {
				if (verbose) {
					System.out.println("501 Not Implemented : " + method + " method.");
				}
				
				// we return the not supported file to the client
				File file = new File(WEB_ROOT, METHOD_NOT_SUPPORTED);
				int fileLength = (int) file.length();
				String contentMimeType = "text/html";
				//read content to return to client
				byte[] fileData = readFileData(file, fileLength);
					
				// we send HTTP Headers with data to client
				out.println("HTTP/1.1 501 Not Implemented");
				out.println("Server: Java HTTP Server from SSaurel : 1.0");
				out.println("Date: " + new Date());
				out.println("Content-type: " + contentMimeType);
				out.println("Content-length: " + fileLength);
				out.println(); // blank line between headers and content, very important !
				out.flush(); // flush character output stream buffer
				// file
				dataOut.write(fileData, 0, fileLength);
				dataOut.flush();
				
			} else {
				// GET or HEAD method
				if (fileRequested.endsWith("/")) {
					fileRequested += DEFAULT_FILE;
				}
				
				File file = new File(WEB_ROOT, fileRequested);
				int fileLength = (int) file.length();
				String content = getContentType(fileRequested);
				
				if (method.equals("GET")) { // GET method so we return content
					byte[] fileData = readFileData(file, fileLength);
					
					// send HTTP Headers
					out.println("HTTP/1.1 200 OK");
					out.println("Server: Java HTTP Server from SSaurel : 1.0");
					out.println("Date: " + new Date());
					out.println("Content-type: " + content);
					out.println("Content-length: " + fileLength);
					out.println(); // blank line between headers and content, very important !
					out.flush(); // flush character output stream buffer
					
					dataOut.write(fileData, 0, fileLength);
					dataOut.flush();
				}
				
				if (verbose) {
					System.out.println("File " + fileRequested + " of type " + content + " returned");
				}
				
			}
			
		} catch (FileNotFoundException fnfe) {
			try {
				fileNotFound(out, dataOut, fileRequested);
			} catch (IOException ioe) {
				System.err.println("Error with file not found exception : " + ioe.getMessage());
			}
			
		} catch (IOException ioe) {
			System.err.println("Server error : " + ioe);
		} finally {
			try {
				in.close();
				out.close();
				dataOut.close();
				connect.close(); // we close socket connection
			} catch (Exception e) {
				System.err.println("Error closing stream : " + e.getMessage());
			} 
			
			if (verbose) {
				System.out.println("Connection closed.\n");
			}
		}
		
		
	}
	
	private byte[] readFileData(File file, int fileLength) throws IOException {
		FileInputStream fileIn = null;
		byte[] fileData = new byte[fileLength];
		
		try {
			fileIn = new FileInputStream(file);
			fileIn.read(fileData);
		} finally {
			if (fileIn != null) 
				fileIn.close();
		}
		
		return fileData;
	}
	
	// return supported MIME Types
	private String getContentType(String fileRequested) {
		if (fileRequested.endsWith(".htm")  ||  fileRequested.endsWith(".html"))
			return "text/html";
		else
			return "text/plain";
	}
	
	private void fileNotFound(PrintWriter out, OutputStream dataOut, String fileRequested) throws IOException {
		File file = new File(WEB_ROOT, FILE_NOT_FOUND);
		int fileLength = (int) file.length();
		String content = "text/html";
		byte[] fileData = readFileData(file, fileLength);
		
		out.println("HTTP/1.1 404 File Not Found");
		out.println("Server: Java HTTP Server from SSaurel : 1.0");
		out.println("Date: " + new Date());
		out.println("Content-type: " + content);
		out.println("Content-length: " + fileLength);
		out.println(); // blank line between headers and content, very important !
		out.flush(); // flush character output stream buffer
		
		dataOut.write(fileData, 0, fileLength);
		dataOut.flush();
		
		if (verbose) {
			System.out.println("File " + fileRequested + " not found");
		}
	}
	
}

Hey. Could you give licensing info on this gist, specifically if I'm allowed to use it for my own projects?

MIT License. You can use it where you want ;)

Hey, great simple Server Project !

Am I right that the HEAD Method is not working properly? - (no header is returned)

In order to fix this, you should probably move the section where the Header is sent (Line 118 to 127) in front of the if where GET requests are filtered (Line 117)