XmlHelper


1   package org.hibernate.ejb.packaging;
2   
3   import java.util.ArrayList  ;
4   import java.util.Iterator  ;
5   
6   import org.w3c.dom.Element  ;
7   import org.w3c.dom.Node  ;
8   import org.w3c.dom.NodeList  ;
9   
10  /**
11   * A utility class to cover up the rough bits of xml parsing
12   *
13   * @author <a HREF="mailto:chris@kimptoc.net">Chris Kimpton</a>
14   * @version $Revision: 1.3 $
15   */
16  public final class XmlHelper {
17      private XmlHelper() {}
18      /**
19       * Returns an iterator over the children of the given element with
20       * the given tag name.
21       *
22       * @param element The parent element
23       * @param tagName The name of the desired child
24       * @return An interator of children or null if element is null.
25       */
26      public static Iterator   getChildrenByTagName(
27              Element   element,
28              String   tagName
29              ) {
30          if ( element == null ) return null;
31          // getElementsByTagName gives the corresponding elements in the whole
32          // descendance. We want only children
33  
34          NodeList   children = element.getChildNodes();
35          ArrayList   goodChildren = new ArrayList  ();
36          for ( int i = 0 ; i < children.getLength() ; i++ ) {
37              Node   currentChild = children.item( i );
38              if ( currentChild.getNodeType() == Node.ELEMENT_NODE &&
39                      ( (Element  ) currentChild ).getTagName().equals( tagName ) ) {
40                  goodChildren.add( (Element  ) currentChild );
41              }
42          }
43          return goodChildren.iterator();
44      }
45  
46      /**
47       * Gets the child of the specified element having the specified unique
48       * name.  If there are more than one children elements with the same name
49       * and exception is thrown.
50       *
51       * @param element The parent element
52       * @param tagName The name of the desired child
53       * @return The named child.
54       * @throws Exception Child was not found or was not unique.
55       */
56      public static Element   getUniqueChild(Element   element, String   tagName)
57              throws Exception   {
58          Iterator   goodChildren = getChildrenByTagName( element, tagName );
59  
60          if ( goodChildren != null && goodChildren.hasNext() ) {
61              Element   child = (Element  ) goodChildren.next();
62              if ( goodChildren.hasNext() ) {
63                  throw new Exception  
64                          ( "expected only one " + tagName + " tag" );
65              }
66              return child;
67          }
68          else {
69              throw new Exception  
70                      ( "expected one " + tagName + " tag" );
71          }
72      }
73  
74      /**
75       * Gets the child of the specified element having the
76       * specified name. If the child with this name doesn't exist
77       * then null is returned instead.
78       *
79       * @param element the parent element
80       * @param tagName the name of the desired child
81       * @return either the named child or null
82       */
83      public static Element   getOptionalChild(Element   element, String   tagName)
84              throws Exception   {
85          return getOptionalChild( element, tagName, null );
86      }
87  
88      /**
89       * Gets the child of the specified element having the
90       * specified name. If the child with this name doesn't exist
91       * then the supplied default element is returned instead.
92       *
93       * @param element        the parent element
94       * @param tagName        the name of the desired child
95       * @param defaultElement the element to return if the child
96       *                       doesn't exist
97       * @return either the named child or the supplied default
98       */
99      public static Element   getOptionalChild(
100             Element   element,
101             String   tagName,
102             Element   defaultElement
103             )
104             throws Exception   {
105         Iterator   goodChildren = getChildrenByTagName( element, tagName );
106 
107         if ( goodChildren != null && goodChildren.hasNext() ) {
108             Element   child = (Element  ) goodChildren.next();
109             if ( goodChildren.hasNext() ) {
110                 throw new Exception  
111                         ( "expected only one " + tagName + " tag" );
112             }
113             return child;
114         }
115         else {
116             return defaultElement;
117         }
118     }
119 
120     /**
121      * Get the content of the given element.
122      *
123      * @param element The element to get the content for.
124      * @return The content of the element or null.
125      */
126     public static String   getElementContent(final Element   element)
127             throws Exception   {
128         return getElementContent( element, null );
129     }
130 
131     /**
132      * Get the content of the given element.
133      *
134      * @param element    The element to get the content for.
135      * @param defaultStr The default to return when there is no content.
136      * @return The content of the element or the default.
137      */
138     public static String   getElementContent(Element   element, String   defaultStr)
139             throws Exception   {
140         if ( element == null ) {
141             return defaultStr;
142         }
143 
144         NodeList   children = element.getChildNodes();
145         String   result = "";
146         for ( int i = 0 ; i < children.getLength() ; i++ ) {
147             if ( children.item( i ).getNodeType() == Node.TEXT_NODE ||
148                     children.item( i ).getNodeType() == Node.CDATA_SECTION_NODE ) {
149                 result += children.item( i ).getNodeValue();
150             }
151             else if ( children.item( i ).getNodeType() == Node.COMMENT_NODE ) {
152                 // Ignore comment nodes
153             }
154         }
155         return result.trim();
156     }
157 
158     /**
159      * Macro to get the content of a unique child element.
160      *
161      * @param element The parent element.
162      * @param tagName The name of the desired child.
163      * @return The element content or null.
164      */
165     public static String   getUniqueChildContent(
166             Element   element,
167             String   tagName
168             )
169             throws Exception   {
170         return getElementContent( getUniqueChild( element, tagName ) );
171     }
172 
173     /**
174      * Macro to get the content of an optional child element.
175      *
176      * @param element The parent element.
177      * @param tagName The name of the desired child.
178      * @return The element content or null.
179      */
180     public static String   getOptionalChildContent(
181             Element   element,
182             String   tagName
183             )
184             throws Exception   {
185         return getElementContent( getOptionalChild( element, tagName ) );
186     }
187 
188     public static boolean getOptionalChildBooleanContent(Element   element, String   name) throws Exception   {
189         Element   child = getOptionalChild( element, name );
190         if ( child != null ) {
191             String   value = getElementContent( child ).toLowerCase();
192             return value.equals( "true" ) || value.equals( "yes" );
193         }
194 
195         return false;
196     }
197 
198 
199 }
200 
201 
202
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