passwordfield.java

一个用java编写的服务器,对于学习网络编程的人来说是个很好的例子

/*
 * This file is part of the QuickServer library 
 * Copyright (C) 2003-2005 QuickServer.org
 *
 * Use, modification, copying and distribution of this software is subject to
 * the terms and conditions of the GNU Lesser General Public License. 
 * You should have received a copy of the GNU LGP License along with this 
 * library; if not, you can download a copy from <http://www.quickserver.org/>.
 *
 * For questions, suggestions, bug-reports, enhancement-requests etc.
 * visit http://www.quickserver.org
 *
 */

package org.quickserver.util.io;

import java.io.*;
import java.util.*;
import java.util.logging.*;

/**
 * This class prompts the user for a password and attempts to mask 
 * input.
 * @since 1.4
 */
public class PasswordField {
	private static Logger logger = Logger.getLogger(PasswordField.class.getName());

	/**
	 * @param prompt The prompt to display to the user.
	 * @return The password as entered by the user.
	 */
	public static final char[] getPassword(String prompt) 
			throws IOException {
	   return getPassword(System.in, prompt);
	}

	/**
	 * @param in input stream to be used (e.g. System.in)
	 * @param prompt The prompt to display to the user.
	 * @return The password as entered by the user.
	 */
	public static final char[] getPassword(InputStream in, String prompt) 
			throws IOException {
		MaskingThread maskingthread = new MaskingThread(prompt);
		Thread thread = new Thread(maskingthread);
		thread.start();

		char[] lineBuffer;
		char[] buf;
		int i;

		buf = lineBuffer = new char[128];

		int room = buf.length;
		int offset = 0;
		int c;

		loop: while(true) {
			c = in.read();
			switch(c) {
				case -1:
				case '\n':
				   break loop;

				case '\r':
				   int c2 = in.read();
				   if((c2 != '\n') && (c2 != -1)) {
					  if(!(in instanceof PushbackInputStream)) {
						 in = new PushbackInputStream(in);
					  }
					  ((PushbackInputStream)in).unread(c2);
					} else {
					  break loop;
					}
				default:
                   if (--room < 0) {
                      buf = new char[offset + 128];
                      room = buf.length - offset - 1;
                      System.arraycopy(lineBuffer, 0, buf, 0, offset);
                      Arrays.fill(lineBuffer, ' ');
                      lineBuffer = buf;
                   }
                   buf[offset++] = (char) c;
                   break;
			}
		}	
		maskingthread.stopMasking();
		System.out.print("\010");
		//Code to clear doskey on win nt/2000 - Alt+F7
		String os = System.getProperty("os.name");
		if(os!=null && os.toLowerCase().startsWith("windows")) {
			try {
				java.awt.Robot robot = new java.awt.Robot();
				robot.keyPress(java.awt.event.KeyEvent.VK_ALT);
				robot.keyPress(java.awt.event.KeyEvent.VK_F7);
				robot.keyRelease(java.awt.event.KeyEvent.VK_F7);
				robot.keyRelease(java.awt.event.KeyEvent.VK_ALT);
			} catch(Exception ignore) {
				logger.warning("Could not clears command history: "+ignore); 
			}
		}

		if(offset == 0) {
			return null;
		}
		char[] ret = new char[offset];
		System.arraycopy(buf, 0, ret, 0, offset);
		Arrays.fill(buf, ' ');
		return ret;
	}
}