XmlHelper


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8     * under the terms of the GNU Lesser General Public License as
9     * published by the Free Software Foundation; either version 2.1 of
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14    * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15    * Lesser General Public License for more details.
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22  package org.jboss.aop.util;
23  
24  import org.w3c.dom.Element  ;
25  import org.w3c.dom.Node  ;
26  import org.w3c.dom.NodeList  ;
27  
28  import java.util.ArrayList  ;
29  import java.util.Iterator  ;
30  
31  /**
32   * A utility class to cover up the rough bits of xml parsing
33   *      
34   * @author <a HREF="mailto:chris@kimptoc.net">Chris Kimpton</a>
35   * @version $Revision: 57391 $
36   */
37  public class XmlHelper
38  {
39     /**
40      * Returns an iterator over the children of the given element with
41      * the given tag name.
42      *
43      * @param element    The parent element
44      * @param tagName    The name of the desired child
45      * @return           An interator of children or null if element is null.
46      */
47     public static Iterator   getChildrenByTagName(Element   element,
48                                                 String   tagName)
49     {
50        if (element == null) return null;
51        // getElementsByTagName gives the corresponding elements in the whole 
52        // descendance. We want only children
53  
54        NodeList   children = element.getChildNodes();
55        ArrayList   goodChildren = new ArrayList  ();
56        for (int i=0; i<children.getLength(); i++) {
57           Node   currentChild = children.item(i);
58           if (currentChild.getNodeType() == Node.ELEMENT_NODE && 
59               ((Element  )currentChild).getTagName().equals(tagName)) {
60              goodChildren.add(currentChild);
61           }
62        }
63        return goodChildren.iterator();
64     }
65  
66     /**
67      * Gets the child of the specified element having the specified unique
68      * name.  If there are more than one children elements with the same name
69      * and exception is thrown.
70      *
71      * @param element    The parent element
72      * @param tagName    The name of the desired child
73      * @return           The named child.
74      *
75      * @throws Exception   Child was not found or was not unique.
76      */
77     public static Element   getUniqueChild(Element   element, String   tagName)
78        throws Exception  
79     {
80        Iterator   goodChildren = getChildrenByTagName(element, tagName);
81  
82        if (goodChildren != null && goodChildren.hasNext()) {
83           Element   child = (Element  )goodChildren.next();
84           if (goodChildren.hasNext()) {
85              throw new Exception  
86                 ("expected only one " + tagName + " tag");
87           }
88           return child;
89        } else {
90           throw new Exception  
91              ("expected one " + tagName + " tag");
92        }
93     }
94  
95     /**
96      * Gets the child of the specified element having the
97      * specified name. If the child with this name doesn't exist
98      * then null is returned instead.
99      *
100     * @param element the parent element
101     * @param tagName the name of the desired child
102     * @return either the named child or null
103     */
104    public static Element   getOptionalChild(Element   element, String   tagName)
105       throws Exception  
106    {
107       return getOptionalChild(element, tagName, null);
108    }
109 
110    /**
111     * Gets the child of the specified element having the
112     * specified name. If the child with this name doesn't exist
113     * then the supplied default element is returned instead.
114     *
115     * @param element the parent element
116     * @param tagName the name of the desired child
117     * @param defaultElement the element to return if the child
118     *                       doesn't exist
119     * @return either the named child or the supplied default
120     */
121    public static Element   getOptionalChild(Element   element,
122                                           String   tagName,
123                                           Element   defaultElement)
124       throws Exception  
125    {
126       Iterator   goodChildren = getChildrenByTagName(element, tagName);
127 
128       if (goodChildren != null && goodChildren.hasNext()) {
129          Element   child = (Element  )goodChildren.next();
130          if (goodChildren.hasNext()) {
131             throw new Exception  
132                ("expected only one " + tagName + " tag");
133          }
134          return child;
135       } else {
136          return defaultElement;
137       }
138    }
139 
140    /**
141     * Get the content of the given element.
142     *
143     * @param element    The element to get the content for.
144     * @return           The content of the element or null.
145     */
146    public static String   getElementContent(final Element   element)
147       throws Exception  
148    {
149       return getElementContent(element, null);
150    }
151 
152    /**
153     * Get the content of the given element.
154     *
155     * @param element       The element to get the content for.
156     * @param defaultStr    The default to return when there is no content.
157     * @return              The content of the element or the default.
158     */
159    public static String   getElementContent(Element   element, String   defaultStr)
160       throws Exception  
161    {
162       if (element == null)
163          return defaultStr;
164 
165       NodeList   children = element.getChildNodes();
166       String   result = "";
167       for (int i = 0; i < children.getLength(); i++)
168       {
169          if (children.item(i).getNodeType() == Node.TEXT_NODE || 
170              children.item(i).getNodeType() == Node.CDATA_SECTION_NODE)
171          {
172             result += children.item(i).getNodeValue();
173          }
174          else if( children.item(i).getNodeType() == Node.COMMENT_NODE )
175          {
176             // Ignore comment nodes
177          }
178       }
179       return result.trim();
180    }
181 
182    /**
183     * Macro to get the content of a unique child element.
184     *
185     * @param element    The parent element.
186     * @param tagName    The name of the desired child.
187     * @return           The element content or null.
188     */
189    public static String   getUniqueChildContent(Element   element,
190                                               String   tagName)
191       throws Exception  
192    {
193       return getElementContent(getUniqueChild(element, tagName));
194    }
195 
196    /**
197     * Macro to get the content of an optional child element.
198     * 
199     * @param element    The parent element.
200     * @param tagName    The name of the desired child.
201     * @return           The element content or null.
202     */
203    public static String   getOptionalChildContent(Element   element,
204                                                 String   tagName)
205       throws Exception  
206    {
207       return getElementContent(getOptionalChild(element, tagName));
208    }
209 
210    public static boolean getOptionalChildBooleanContent(Element   element, String   name) throws Exception  
211    {
212       Element   child = getOptionalChild(element, name);
213       if(child != null)
214       {
215          String   value = getElementContent(child).toLowerCase();
216          return value.equals("true") || value.equals("yes");
217       }
218 
219       return false;
220    }
221 
222 
223 }
224 
225 
226
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