xmlutil.java

老外的在线考试

/*
 * Core - Library of useful classes that are used in many CyberDemia projects.
 * Copyright (C) 2003 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.xml;
import org.w3c.dom.*;
import java.util.ArrayList;

/**
* XMLUtil is a utility class to faciliate usage of XML DOM. 
* They should be useful throughout many projects in CyberDemia.
* @author Alexander Yap
*/ 
public class XMLUtil
{

	/**
	* Gets named attribute of specified element as a String.
	* The context is provided for exception messages.
	* @param elem              Element to access.
	* @param attributeName     Name of attribute
	* @param context           Description of this element's context (may be null)      
	* @return Attribute as a String.
	* @exception XMLUtilException  if the named attribute does not exist in elem.
	*/
	public static String getStringAttribute( Element elem, String attributeName, String context )
		throws XMLUtilException
	{
		String strAttr = elem.getAttribute(attributeName);
		if (strAttr==null)
			throw new XMLUtilException("Null attribute "+attributeName, elem.getTagName(), context);
		if (strAttr.length()==0)
			throw new XMLUtilException("Empty attribute "+attributeName, elem.getTagName(), context);
		return strAttr;
	}

	/**
	* Gets named attribute of specified element as an int.
	* The context is provided for exception messages.
	* @param elem              Element to access.
	* @param attributeName     Name of attribute
	* @param context           Description of this element's context (may be null)      
	* @return Attribute as an int.
	* @exception XMLUtilException  
	*    if the named attribute does not exist in elem, or the value cannot be converted to an int.
	*/
	public static int getIntAttribute( Element elem, String attributeName, String context )
		throws XMLUtilException
	{
		String strAttr = getStringAttribute(elem,attributeName,context);
		int intAttr = 0;
		try
		{
			intAttr = Integer.parseInt( strAttr );
		}
		catch (NumberFormatException nfex)
		{
			throw new XMLUtilException("Error converting "+strAttr+" to int", elem.getTagName(), context);
		}
		return intAttr;
	}

	/**
	* Gets all named child elements from its parent element.
	* The context is provided for exception messages.
	* @param parentElem        Parent element.
	* @param elemName          Name of elements to get.
	* @param context           Description of this element's context (may be null)
	* @return Array of Named elements, or empty array if no matching child found.
	*/
	public static Element[] getChildElements( Element parentElem, String elemName, String context)
	{
		ArrayList matchList = new ArrayList();
		NodeList nodeList = parentElem.getChildNodes();
		for (int i=0; i<nodeList.getLength(); i++)
		{
			Node child = nodeList.item(i);
			if ((child instanceof Element) && child.getNodeName().equals(elemName))
			{
				matchList.add(child);
			}
		}

		return (Element[])matchList.toArray(new Element[0]);
	}

	/**
	* Gets first named element from its parent element. This parent element must
	* contain at least one child element of this name.
	* The context is provided for exception messages.
	* @param parentElem        Parent element.
	* @param elemName          Name of element to get.
	* @param context           Description of this element's context (may be null)
	* @return Named element, or null if none.
	*/
	public static Element getSingleElement( Element parentElem, String elemName, String context)
	{
		NodeList nodeList = parentElem.getChildNodes();
		Element elem = null;
		for (int i=0; i<nodeList.getLength(); i++)
		{
			Node child = nodeList.item(i);
			if ((child instanceof Element) && child.getNodeName().equals(elemName))
			{
				elem = (Element)child;
				break;
			}
		}
		return elem;
	}

	/**
	* Gets the value contained in a named element as a String, given the parent element.
	* This parent element must contain at least one child element of this name.
	* The context is provided for exception messages.
	* @param parentElem        Parent element.
	* @param elemName          Name of element to access.
	* @param context           Description of this element's context (may be null)
	* @return Value contained in element as a String.
	* @exception XMLUtilException
	*    if there is not at least one such child element in parentElem.
	*/
	public static String getSingleElementStringValue( Element parentElem, String elemName, String context)
		throws XMLUtilException
	{
		Element elem = getSingleElement(parentElem, elemName, context);
		if (elem==null)
		{
			throw new XMLUtilException("Missing element",elemName,context);
		}
		return getStringValue(elem, context);
	}

	/**
	* Gets the value contained in the specified element as a String.
	* The context is provided for exception messages.
	* @param elem              Element to access.   
	* @param context           Description of this element's context (may be null)      
	* @return Value contained in element as a String.
	* @exception XMLUtilException  
	*    if there is an error.
	*/
	public static String getStringValue( Element elem, String context)
		throws XMLUtilException
	{
		elem.normalize();
		if (!elem.hasChildNodes())
			throw new XMLUtilException("Missing value", elem.getTagName(), context);
		Node firstNode = elem.getFirstChild();
		if (firstNode.getNodeType()!=Node.TEXT_NODE)
			throw new XMLUtilException("Invalid data type, expecting TEXT", elem.getTagName(), context);

		return ((Text)firstNode).getData();		
	}

	/**
	* Gets the value contained in a named element as an int, given the parent element. 
	* This parent element must contain at least one child element of this name.
	* The context is provided for exception messages.
	* @param parentElem        Parent element.
	* @param elemName          Name of element to access.   
	* @param context           Description of this element's context (may be null)      
	* @return Value contained in element as an int.
	* @exception XMLUtilException  
	*    if there is not at least one such child element in parentElem,
	*    or the value cannot be converted to an int.
	*/
	public static int getSingleElementIntValue( Element parentElem, String elemName, String context)
		throws XMLUtilException
	{
		Element elem = getSingleElement(parentElem, elemName, context);
		if (elem==null)
		{
			throw new XMLUtilException("Missing element",elemName,context);
		}
		return getIntValue(elem, context);
	}

	/**
	* Gets the value contained in the specified element as an int.
	* The context is provided for exception messages.
	* @param elem              Element to access.   
	* @param context           Description of this element's context (may be null)      
	* @return Value contained in element as an int .
	* @exception XMLUtilException  
	*    if there is an error.
	*/
	public static int getIntValue( Element elem, String context)
		throws XMLUtilException
	{
		String strVal = getStringValue(elem, context);
		int intVal = 0;
		try
		{
			intVal = Integer.parseInt( strVal );
		}
		catch (NumberFormatException nfex)
		{
			throw new XMLUtilException("Error converting "+strVal+" to int", elem.getTagName(), context);
		}
		return intVal;
	}

	/**
	* Gets the value contained in a named element as a byte, given the parent element. 
	* This parent element must contain at least one child element of this name.
	* The context is provided for exception messages.
	* @param parentElem        Parent element.
	* @param elemName          Name of element to access.   
	* @param context           Description of this element's context (may be null)      
	* @return Value contained in element as a byte.
	* @exception XMLUtilException  
	*    if there is not at least one such child element in parentElem,
	*    or the value cannot be converted to a byte.
	*/
	public static byte getSingleElementByteValue( Element parentElem, String elemName, String context)
		throws XMLUtilException
	{
		Element elem = getSingleElement(parentElem, elemName, context);
		if (elem==null)
		{
			throw new XMLUtilException("Missing element",elemName,context);
		}
		return getByteValue(elem, context);
	}

	/**
	* Gets the value contained in the specified element as a byte.
	* The context is provided for exception messages.
	* @param elem              Element to access.   
	* @param context           Description of this element's context (may be null)      
	* @return Value contained in element as a byte.
	* @exception XMLUtilException  
	*    if there is an error.
	*/
	public static byte getByteValue( Element elem, String context)
		throws XMLUtilException
	{
		String strVal = getStringValue(elem, context);
		byte byteVal = 0;
		try
		{
			byteVal = Byte.parseByte( strVal );
		}
		catch (NumberFormatException nfex)
		{
			throw new XMLUtilException("Error converting "+strVal+" to byte", elem.getTagName(), context);
		}
		return byteVal;
	}


	/**
	* <p>
	* Encodes pre-formatted text to safely preserve certain 
	* non-alphanumeric characters such as mathematical symbols, 
	* spaces and new lines.
	* All characters that are not letters or digits are encoded.
	* </p>
	* <p>
	* The encoded text can be safely stored as content of an XML element.
	* However, if you want to display the pre-formatted text with XHTML 
	* in a Web browser, you must put it inside the 
	* <code>&lt;pre&gt;</code> element, or with the equivalent style-sheet.
	* </p>
	*
	* @param text Formatted text to be encoded. 
	* @return Encoded text.
	*/
	public static String encodeText(String text)
	{
		// Estimate encoded text to be 3 times bigger than original
		StringBuffer encoded = new StringBuffer(3*text.length());
		for (int cidx=0; cidx<text.length(); cidx++)
		{
			char ch = text.charAt(cidx);	
			if (Character.isLetterOrDigit(ch))
				encoded.append(ch);
			else
				encoded.append("&#"+Integer.toString((int)ch)+";");
		}
		
		return encoded.toString();
	}

}