Java 实现 web服务器的简单实例

时间：2021-05-28

Java 实现 web服务器的简单实例

实例代码：

import java.util.*; // Chapter 8, Listing 3 public class WebServerDemo { // Directory of HTML pages and other files protected String docroot; // Port number of web server protected int port; // Socket for the web server protected ServerSocket ss; // Handler for a HTTP request class Handler extends Thread { protected Socket socket; protected PrintWriter pw; protected BufferedOutputStream bos; protected BufferedReader br; protected File docroot; public Handler(Socket _socket, String _docroot) throws Exception { socket = _socket; // Get the absolute directory of the filepath docroot = new File(_docroot).getCanonicalFile(); } public void run() { try { // Prepare our readers and writers br = new BufferedReader(new InputStreamReader( socket.getInputStream())); bos = new BufferedOutputStream(socket.getOutputStream()); pw = new PrintWriter(new OutputStreamWriter(bos)); // Read HTTP request from user (hopefully GET /file...... ) String line = br.readLine(); // Shutdown any further input socket.shutdownInput(); if (line == null) { socket.close(); return; } if (line.toUpperCase().startsWith("GET")) { // Eliminate any trailing ? data, such as for a CGI GET // request StringTokenizer tokens = new StringTokenizer(line, " ?"); tokens.nextToken(); String req = tokens.nextToken(); // If a path character / or / is not present, add it to the // document root // and then add the file request, to form a full filename String name; if (req.startsWith("/") || req.startsWith("//")) name = this.docroot + req; else name = this.docroot + File.separator + req; // Get absolute file path File file = new File(name).getCanonicalFile(); // Check to see if request doesn't start with our document // root .... if (!file.getAbsolutePath().startsWith( this.docroot.getAbsolutePath())) { pw.println("HTTP/1.0 403 Forbidden"); pw.println(); } // ... if it's missing ..... else if (!file.exists()) { pw.println("HTTP/1.0 404 File Not Found"); pw.println(); } // ... if it can't be read for security reasons .... else if (!file.canRead()) { pw.println("HTTP/1.0 403 Forbidden"); pw.println(); } // ... if its actually a directory, and not a file .... else if (file.isDirectory()) { sendDir(bos, pw, file, req); } // ... or if it's really a file else { sendFile(bos, pw, file.getAbsolutePath()); } } // If not a GET request, the server will not support it else { pw.println("HTTP/1.0 501 Not Implemented"); pw.println(); } pw.flush(); bos.flush(); } catch (Exception e) { e.printStackTrace(); } try { socket.close(); } catch (Exception e) { e.printStackTrace(); } } protected void sendFile(BufferedOutputStream bos, PrintWriter pw, String filename) throws Exception { try { java.io.BufferedInputStream bis = new java.io.BufferedInputStream( new FileInputStream(filename)); byte[] data = new byte[10 * 1024]; int read = bis.read(data); pw.println("HTTP/1.0 200 Okay"); pw.println(); pw.flush(); bos.flush(); while (read != -1) { bos.write(data, 0, read); read = bis.read(data); } bos.flush(); } catch (Exception e) { pw.flush(); bos.flush(); } } protected void sendDir(BufferedOutputStream bos, PrintWriter pw, File dir, String req) throws Exception { try { pw.println("HTTP/1.0 200 Okay"); pw.println(); pw.flush(); pw.print("<html><head><title>Directory of "); pw.print(req); pw.print("</title></head><body><h1>Directory of "); pw.print(req); pw.println("</h1><table border=/"0/">"); File[] contents = dir.listFiles(); for (int i = 0; i < contents.length; i++) { pw.print("<tr>"); pw.print("<td><a href="/" rel="external nofollow" rel="external nofollow" mce_href="/" rel="external nofollow" rel="external nofollow" ""); pw.print(req); pw.print(contents[i].getName()); if (contents[i].isDirectory()) pw.print("/"); pw.print("/">"); if (contents[i].isDirectory()) pw.print("Dir -> "); pw.print(contents[i].getName()); pw.print("</a></td>"); pw.println("</tr>"); } pw.println("</table></body></html>"); pw.flush(); } catch (Exception e) { pw.flush(); bos.flush(); } } } // Check that a filepath has been specified and a port number protected void parseParams(String[] args) throws Exception { switch (args.length) { case 1: case 0: System.err.println("Syntax: <jvm> " + this.getClass().getName() + " docroot port"); System.exit(0); default: this.docroot = args[0]; this.port = Integer.parseInt(args[1]); break; } } public WebServerDemo(String[] args) throws Exception { System.out.println("Checking for paramters"); // Check for command line parameters parseParams(args); System.out.print("Starting web server...... "); // Create a new server socket this.ss = new ServerSocket(this.port); System.out.println("OK"); for (;;) { // Accept a new socket connection from our server socket Socket accept = ss.accept(); // Start a new handler instance to process the request new Handler(accept, docroot).start(); } } // Start an instance of the web server running public static void main(String[] args) throws Exception { WebServerDemo webServerDemo = new WebServerDemo(args); } }

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