Saját HTTP szerver mintapélda

Készítsünk egy üres Java projektet, hozzunk létre egy 404.html és egy index.html nevű fájlt az alábbi tartalommal. Majd figyeljük meg hogy a hibakezelés redundáns, azaz kétszer van megírva 404 és 501-es hiba kezelése.

Feladat: készítsen egy általános hibakezelő függvényt a hibák kliens oldalra visszadására.

404.html tartalma: 

    <html>
        <body>
        <h1>File not found error</h1>
        </body>
    </html>

index.html tartalma: 

    <html>
    <body>
    <h1>My HTTP server works</h1>
    <a href="/dead_link.html">Link not working</a>
    </body>
    </html>

JavaHTTPServer.java tartalma: 

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;

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";

	private Socket connect;

	public JavaHTTPServer(Socket c) {
		connect = c;
	}

	public static void main(String[] args) {
		try {
			ServerSocket serverConnect = new ServerSocket(8080);
			System.out.println("Server started.\nListening for connections on port : 8080 ...\n");

			while (true) {
				JavaHTTPServer myServer = new JavaHTTPServer(serverConnect.accept());

				Thread thread = new Thread(myServer);
				thread.start();
			}
		} catch (IOException e) {
			System.err.println("Server Connection error : " + e.getMessage());
		}
	}

	@Override
	public void run() {
		BufferedReader in = null;
		PrintWriter out = null;
		BufferedOutputStream dataOut = null;
		String fileRequested = null;

		try {
			in = new BufferedReader(new InputStreamReader(connect.getInputStream()));
			out = new PrintWriter(connect.getOutputStream());
			dataOut = new BufferedOutputStream(connect.getOutputStream());

			String input = in.readLine();

			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")) {
				// 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 v1.0");
					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();
				}
			}

		} 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());
			}
		}

	}

	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 v1.0");
		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();
	}

}

Feladat: refaktoráljuk a kódot és szüntessük meg a többszörözött részeket. Készítsünk egy külön függvényt a HTTP válasz általános visszadásához: 

out.println("HTTP/1.1 200 OK");
out.println("Server: Java HTTP Server v1.0");
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

Feladat: módosítsuk a forráskódot, hogy képeket is vissza tudjon adni. Ehhez először <img src=„…> kiegészítést adjunk hozzá a index.html-nek és másoljunk egy tetszőleges képet a html-ek mellé.