XmlHelper


1   /*
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3     * Copyright 2005, JBoss Inc., and individual contributors as indicated
4     * by the @authors tag. See the copyright.txt in the distribution for a
5     * full listing of individual contributors.
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7     * This is free software; you can redistribute it and/or modify it
8     * under the terms of the GNU Lesser General Public License as
9     * published by the Free Software Foundation; either version 2.1 of
10    * the License, or (at your option) any later version.
11    *
12    * This software is distributed in the hope that it will be useful,
13    * but WITHOUT ANY WARRANTY; without even the implied warranty of
14    * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15    * Lesser General Public License for more details.
16    *
17    * You should have received a copy of the GNU Lesser General Public
18    * License along with this software; if not, write to the Free
19    * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
20    * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
21    */
22  package org.jboss.util.xml;
23  
24  import java.io.Writer  ;
25  import java.util.ArrayList  ;
26  import java.util.Iterator  ;
27  
28  import org.w3c.dom.Document  ;
29  import org.w3c.dom.Element  ;
30  import org.w3c.dom.Node  ;
31  import org.w3c.dom.NodeList  ;
32  
33  /**
34   * A utility class to cover up the rough bits of xml parsing
35   *      
36   * @author <a HREF="mailto:chris@kimptoc.net">Chris Kimpton</a>
37   * @version $Revision: 1958 $
38   */
39  public class XmlHelper
40  {
41     public static void write(Writer   out, Document   dom)
42        throws Exception  
43     {
44        new DOMWriter(out).setPrettyprint(true).print(dom);
45     }
46  
47     /**
48      * Returns an iterator over the children of the given element with
49      * the given tag name.
50      *
51      * @param element    The parent element
52      * @param tagName    The name of the desired child
53      * @return           An interator of children or null if element is null.
54      */
55     public static Iterator   getChildrenByTagName(Element   element,
56                                                 String   tagName)
57     {
58        if (element == null) return null;
59        // getElementsByTagName gives the corresponding elements in the whole 
60        // descendance. We want only children
61  
62        NodeList   children = element.getChildNodes();
63        ArrayList   goodChildren = new ArrayList  ();
64        for (int i=0; i<children.getLength(); i++) {
65           Node   currentChild = children.item(i);
66           if (currentChild.getNodeType() == Node.ELEMENT_NODE && 
67               ((Element  )currentChild).getTagName().equals(tagName)) {
68              goodChildren.add((Element  )currentChild);
69           }
70        }
71        return goodChildren.iterator();
72     }
73  
74     /**
75      * Gets the child of the specified element having the specified unique
76      * name.  If there are more than one children elements with the same name
77      * and exception is thrown.
78      *
79      * @param element    The parent element
80      * @param tagName    The name of the desired child
81      * @return           The named child.
82      *
83      * @throws Exception   Child was not found or was not unique.
84      */
85     public static Element   getUniqueChild(Element   element, String   tagName)
86        throws Exception  
87     {
88        Iterator   goodChildren = getChildrenByTagName(element, tagName);
89  
90        if (goodChildren != null && goodChildren.hasNext()) {
91           Element   child = (Element  )goodChildren.next();
92           if (goodChildren.hasNext()) {
93              throw new Exception  
94                 ("expected only one " + tagName + " tag");
95           }
96           return child;
97        } else {
98           throw new Exception  
99              ("expected one " + tagName + " tag");
100       }
101    }
102 
103    /**
104     * Gets the child of the specified element having the
105     * specified name. If the child with this name doesn't exist
106     * then null is returned instead.
107     *
108     * @param element the parent element
109     * @param tagName the name of the desired child
110     * @return either the named child or null
111     */
112    public static Element   getOptionalChild(Element   element, String   tagName)
113       throws Exception  
114    {
115       return getOptionalChild(element, tagName, null);
116    }
117 
118    /**
119     * Gets the child of the specified element having the
120     * specified name. If the child with this name doesn't exist
121     * then the supplied default element is returned instead.
122     *
123     * @param element the parent element
124     * @param tagName the name of the desired child
125     * @param defaultElement the element to return if the child
126     *                       doesn't exist
127     * @return either the named child or the supplied default
128     */
129    public static Element   getOptionalChild(Element   element,
130                                           String   tagName,
131                                           Element   defaultElement)
132       throws Exception  
133    {
134       Iterator   goodChildren = getChildrenByTagName(element, tagName);
135 
136       if (goodChildren != null && goodChildren.hasNext()) {
137          Element   child = (Element  )goodChildren.next();
138          if (goodChildren.hasNext()) {
139             throw new Exception  
140                ("expected only one " + tagName + " tag");
141          }
142          return child;
143       } else {
144          return defaultElement;
145       }
146    }
147 
148    /**
149     * Get the content of the given element.
150     *
151     * @param element    The element to get the content for.
152     * @return           The content of the element or null.
153     */
154    public static String   getElementContent(final Element   element)
155       throws Exception  
156    {
157       return getElementContent(element, null);
158    }
159 
160    /**
161     * Get the content of the given element.
162     *
163     * @param element       The element to get the content for.
164     * @param defaultStr    The default to return when there is no content.
165     * @return              The content of the element or the default.
166     */
167    public static String   getElementContent(Element   element, String   defaultStr)
168       throws Exception  
169    {
170       if (element == null)
171          return defaultStr;
172 
173       NodeList   children = element.getChildNodes();
174       String   result = "";
175       for (int i = 0; i < children.getLength(); i++)
176       {
177          if (children.item(i).getNodeType() == Node.TEXT_NODE || 
178              children.item(i).getNodeType() == Node.CDATA_SECTION_NODE)
179          {
180             result += children.item(i).getNodeValue();
181          }
182          else if( children.item(i).getNodeType() == Node.COMMENT_NODE )
183          {
184             // Ignore comment nodes
185          }
186       }
187       return result.trim();
188    }
189 
190    /**
191     * Macro to get the content of a unique child element.
192     *
193     * @param element    The parent element.
194     * @param tagName    The name of the desired child.
195     * @return           The element content or null.
196     */
197    public static String   getUniqueChildContent(Element   element,
198                                               String   tagName)
199       throws Exception  
200    {
201       return getElementContent(getUniqueChild(element, tagName));
202    }
203 
204    /**
205     * Macro to get the content of an optional child element.
206     * 
207     * @param element    The parent element.
208     * @param tagName    The name of the desired child.
209     * @return           The element content or null.
210     */
211    public static String   getOptionalChildContent(Element   element,
212                                                 String   tagName)
213       throws Exception  
214    {
215       return getElementContent(getOptionalChild(element, tagName));
216    }
217 
218    public static boolean getOptionalChildBooleanContent(Element   element, String   name) throws Exception  
219    {
220       Element   child = getOptionalChild(element, name);
221       if(child != null)
222       {
223          String   value = getElementContent(child).toLowerCase();
224          return value.equals("true") || value.equals("yes");
225       }
226 
227       return false;
228    }
229 
230 
231 }
232 
233 
234
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