Lucene example source code file (DOMUtils.java)

This example Lucene source code file (DOMUtils.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Lucene tags/keywords

document, documentbuilderfactory, dom, domutils, element, element, exception, io, node, node, parser, parserexception, parserexception, runtimeexception, sax, string, string, stringbuilder, xml

The Lucene DOMUtils.java source code

package org.apache.lucene.xmlparser;
import java.io.Reader;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.xml.sax.InputSource;
/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * 
 */
public class DOMUtils
{
    public static Element getChildByTagOrFail(Element e, String name)	throws ParserException
	{
		Element kid = getChildByTagName(e, name);
		if (null == kid)
		{
			throw new ParserException(e.getTagName() + " missing \"" + name
					+ "\" child element");
		}
		return kid;
	}
     
     public static Element getFirstChildOrFail(Element e) throws ParserException
	{
		Element kid = getFirstChildElement(e);
		if (null == kid)
		{
			throw new ParserException(e.getTagName()
					+ " does not contain a child element");
		}
		return kid;
	}
     
	public static String getAttributeOrFail(Element e, String name)	throws ParserException
	{
		String v = e.getAttribute(name);
		if (null == v)
		{
			throw new ParserException(e.getTagName() + " missing \"" + name
					+ "\" attribute");
		}
		return v;
	}
    public static String getAttributeWithInheritanceOrFail(Element e,	String name) throws ParserException
	{
		String v = getAttributeWithInheritance(e, name);
		if (null == v)
		{
			throw new ParserException(e.getTagName() + " missing \"" + name
					+ "\" attribute");
		}
		return v;
	}
    public static String getNonBlankTextOrFail(Element e) throws ParserException
	{
		String v = getText(e);
		if (null != v)
			v = v.trim();
		if (null == v || 0 == v.length())
		{
			throw new ParserException(e.getTagName() + " has no text");
		}
		return v;
	}
 
     
     
     
	
	
	/* Convenience method where there is only one child Element of a given name */
	public static Element getChildByTagName(Element e, String name)
	{
	       for (Node kid = e.getFirstChild(); kid != null; kid = kid.getNextSibling())
		{
			if( (kid.getNodeType()==Node.ELEMENT_NODE) && (name.equals(kid.getNodeName())) )
			{
				return (Element)kid;
			}
		}
		return null;
	}

	/**
	 * Returns an attribute value from this node, or first parent node with this attribute defined
	 * @param element 
	 * @param attributeName
	 * @return A non-zero-length value if defined, otherwise null
	 */
	public static String getAttributeWithInheritance(Element element, String attributeName)
	{
		String result=element.getAttribute(attributeName);
		if( (result==null)|| ("".equals(result) ) )
		{
			Node n=element.getParentNode();
			if((n==element)||(n==null))
			{
				return null;
			}
			if(n instanceof Element)
			{
				Element parent=(Element) n;
				return getAttributeWithInheritance(parent,attributeName);
			}
			return null; //we reached the top level of the document without finding attribute
		}
		return result;		
	}



	/* Convenience method where there is only one child Element of a given name */
	public static String getChildTextByTagName(Element e, String tagName)
	{
		Element child=getChildByTagName(e,tagName);
		if(child!=null)
		{
			return getText(child);
		}
		return null;
	}

	/* Convenience method to append a new child with text*/
	public static Element insertChild(Element parent, String tagName, String text)
	{
	  	Element child = parent.getOwnerDocument().createElement(tagName);
		parent.appendChild(child);
		if(text!=null)
		{
		  	child.appendChild(child.getOwnerDocument().createTextNode(text));
		}
		return child;
	}

	public static String getAttribute(Element element, String attributeName, String deflt)
	{
		String result=element.getAttribute(attributeName);
		if( (result==null)|| ("".equals(result) ) )
		{
			return deflt;
		}
		return result;
	}
	public static float getAttribute(Element element, String attributeName, float deflt)
	{
		String result=element.getAttribute(attributeName);
		if( (result==null)|| ("".equals(result) ) )
		{
			return deflt;
		}
		return Float.parseFloat(result);
	}	

	public static int getAttribute(Element element, String attributeName, int deflt)
	{
		String result=element.getAttribute(attributeName);
		if( (result==null)|| ("".equals(result) ) )
		{
			return deflt;
		}
		return Integer.parseInt(result);
	}
	
	public static boolean getAttribute(Element element, String attributeName,
			boolean deflt)
	{
		String result = element.getAttribute(attributeName);
		if ((result == null) || ("".equals(result)))
		{
			return deflt;
		}
		return Boolean.valueOf(result).booleanValue();
	}	

	/* Returns text of node and all child nodes - without markup */
	//MH changed to Node from Element 25/11/2005
	public static String getText(Node e)
	{
		StringBuilder sb=new StringBuilder();
		getTextBuffer(e, sb);
		return sb.toString();
	}
	
	public static Element getFirstChildElement(Element element)
	{
		for (Node kid = element.getFirstChild(); kid != null; kid = kid
				.getNextSibling())
		{
			if (kid.getNodeType() == Node.ELEMENT_NODE) 
			{
				return (Element) kid;
			}
		}
		return null;
	}	

	private static void getTextBuffer(Node e, StringBuilder sb)
	{
	    for (Node kid = e.getFirstChild(); kid != null; kid = kid.getNextSibling())
		{
			switch(kid.getNodeType())
			{
				case Node.TEXT_NODE:
				{
					sb.append(kid.getNodeValue());
					break;
				}
				case Node.ELEMENT_NODE:
				{
					getTextBuffer(kid, sb);
					break;
				}
				case Node.ENTITY_REFERENCE_NODE:
				{
					getTextBuffer(kid, sb);
					break;
				}
			}
		}
	}

	/**
	* Helper method to parse an XML file into a DOM tree, given a reader.
	* @param is reader of the XML file to be parsed
	* @return an org.w3c.dom.Document object
	*/
	public static Document loadXML(Reader is)
	{

		DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
		DocumentBuilder db = null;
		
		try
		{
			db = dbf.newDocumentBuilder();
		}
		catch (Exception se)
		{
			throw new RuntimeException("Parser configuration error", se);
		}

		// Step 3: parse the input file
		org.w3c.dom.Document doc = null;
		try
		{
			doc = db.parse(new InputSource(is));
			//doc = db.parse(is);
		}
		catch (Exception se)
		{
			throw new RuntimeException("Error parsing file:" + se, se);
		}

		return doc;
	}	
}