jsstringtag.java

老外的在线考试

/*
 * Core - Library of useful classes that are used in many CyberDemia projects.
 * Copyright (C) 2004 CyberDemia Research and Services
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA  02111-1307, USA.
 *
 * See the COPYING file located in the top-level-directory of
 * the archive of this library for complete text of license.
 */
package com.cyberdemia.jsp;

import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import java.io.IOException;

/**
 * JSStringTag encodes its body to ensure that it can be safely used as a
 * Javascript String literal.
 * 
 * @author Alexander Yap
 * @version $Revision: 1.1 $ at $Date: 2004/03/22 06:56:39 $ by $Author: alexycyap $
 *  
 */
public class JSStringTag extends BodyTagSupport
{

	public int doAfterBody() throws JspException
	{
		BodyContent body = getBodyContent();
		String encodedStr = encodeJSString(body.getString());
		body.clearBody();
		try
		{

			getPreviousOut().print(encodedStr);
		}
		catch (IOException ioex)
		{
			throw new JspException("Error rewriting encoded Url " + encodedStr,
					ioex);
		}
		return SKIP_BODY;
	}

	static public String encodeJSString(String text)
	{
		if (text == null) { return ""; }

		char[] tempChars = text.toCharArray();
		StringBuffer buffer = new StringBuffer();
		for (int i = 0; i < tempChars.length; i++)
		{
			char ch = tempChars[i];
			switch (ch)
			{
				case '\'':
					buffer.append('\\');
					buffer.append('\'');
					break;
				case '\"':
					buffer.append('\\');
					buffer.append('\"');
					break;
				case '\\':
					if (i < tempChars.length - 1)
					{ // Allows \n to be interpreted as new line inside
					// Javascript String
						if (tempChars[i + 1] == 'n')
						{
							buffer.append(ch);
							break;
						}
					}
					buffer.append('\\');
					buffer.append('\\');
					break;
				default:
					// Escape all other characters that are not letters,
					// numbers or whitespaces
					if (Character.isLetterOrDigit(ch)
							|| Character.isWhitespace(ch))
					{
						buffer.append(ch);
					} else
					{
						String hexStr = Integer.toHexString(ch);
						int hexStrLen = hexStr.length();
						if (hexStrLen == 1)
						{
							hexStr = "0" + hexStr;
						} else if (hexStrLen > 2)
						{
							hexStr = hexStr.substring(hexStrLen - 2, hexStrLen);
						}
						buffer.append("\\x");
						buffer.append(hexStr);
					}
			}
		}
		return buffer.toString();
	}

}