XRTreeFrag


1   /*
2    * Copyright 1999-2004 The Apache Software Foundation.
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    *     http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  /*
17   * $Id: XRTreeFrag.java,v 1.30 2004/02/17 04:34:38 minchau Exp $
18   */
19  package org.apache.xpath.objects;
20  
21  import org.apache.xml.dtm.DTM;
22  import org.apache.xml.dtm.DTMIterator;
23  import org.apache.xml.utils.XMLString;
24  import org.apache.xpath.Expression;
25  import org.apache.xpath.ExpressionNode;
26  import org.apache.xpath.XPathContext;
27  import org.apache.xpath.axes.RTFIterator;
28  
29  import org.w3c.dom.NodeList  ;
30  
31  /**
32   * This class represents an XPath result tree fragment object, and is capable of
33   * converting the RTF to other types, such as a string.
34   * @xsl.usage general
35   */
36  public class XRTreeFrag extends XObject implements Cloneable  
37  {
38    DTM m_dtm;
39    int m_dtmRoot;
40    XPathContext m_xctxt;
41    boolean m_allowRelease = false;
42  
43  //  /**
44  //   * Create an XRTreeFrag Object.
45  //   *
46  //   * @param frag Document fragment this will wrap
47  //   */
48  //  public XRTreeFrag(DTMIterator frag)
49  //  {
50  //    super(frag);
51  //    
52  //    // Obviously, this constructor should be avoided when possible.
53  //    m_dtmRoot = frag.cloneWithReset().nextNode();
54  //  }
55    
56    /**
57     * Create an XRTreeFrag Object.
58     *
59     * @param frag Document fragment this will wrap
60     */
61    public XRTreeFrag(int root, XPathContext xctxt, ExpressionNode parent)
62    {
63      super(null);
64      
65      // Obviously, this constructor should be avoided when possible.
66      exprSetParent(parent);
67      m_dtmRoot = root;
68      m_xctxt = xctxt;
69      m_dtm = xctxt.getDTM(root);
70    }
71    
72    /**
73     * Create an XRTreeFrag Object.
74     *
75     * @param frag Document fragment this will wrap
76     */
77    public XRTreeFrag(int root, XPathContext xctxt)
78    {
79      super(null);
80      
81      // Obviously, this constructor should be avoided when possible.
82      m_dtmRoot = root;
83      m_xctxt = xctxt;
84      m_dtm = xctxt.getDTM(root);
85    }
86  
87    
88    /**
89     * Return a java object that's closest to the representation
90     * that should be handed to an extension.
91     *
92     * @return The object that this class wraps
93     */
94    public Object   object()
95    {
96      if (m_xctxt != null)
97        return new org.apache.xml.dtm.ref.DTMNodeIterator((DTMIterator)(new org.apache.xpath.NodeSetDTM(m_dtmRoot, m_xctxt.getDTMManager())));
98      else
99        return super.object();
100   }
101   
102   /**
103    * Create an XRTreeFrag Object.
104    *
105    * @param frag Document fragment this will wrap
106    */
107   public XRTreeFrag(Expression expr)
108   {
109     super(expr);
110   }
111   
112   /**
113    * Release any resources this object may have by calling destruct().
114    * %ISSUE% This release will occur asynchronously. Resources it manipulates
115    * MUST be thread-safe!
116    *
117    * @throws Throwable
118    */
119   protected void finalize() throws Throwable  
120   {
121     try
122     {
123       destruct();
124     }
125     finally
126     {
127       super.finalize();  // Always use this.
128     }
129   }
130   
131   /**
132    * Specify if it's OK for detach to release the iterator for reuse.
133    * 
134    * @param allowRelease true if it is OK for detach to release this iterator 
135    * for pooling.
136    */
137   public void allowDetachToRelease(boolean allowRelease)
138   {
139     m_allowRelease = allowRelease;
140   }
141 
142   /**
143    * Detaches the <code>DTMIterator</code> from the set which it iterated
144    * over, releasing any computational resources and placing the iterator
145    * in the INVALID state. After <code>detach</code> has been invoked,
146    * calls to <code>nextNode</code> or <code>previousNode</code> will
147    * raise a runtime exception.
148    * 
149    * In general, detach should only be called once on the object.
150    */
151   public void detach()
152   {
153     if(m_allowRelease)
154     {
155         // %REVIEW% Do we actually _need_ detach, now that DTM RTF
156         // storage is managed as a stack?
157       // See #destruct() for a comment about this next check.
158       int ident = m_xctxt.getDTMIdentity(m_dtm);
159       DTM foundDTM = m_xctxt.getDTM(ident);      
160       if(foundDTM == m_dtm)
161       {
162         m_xctxt.release(m_dtm, true);
163         m_dtm = null;
164         m_xctxt = null;
165       }
166       m_obj = null;
167     }
168   }
169   
170   /**
171    * Forces the object to release it's resources.  This is more harsh than 
172    * detach().  You can call destruct as many times as you want.
173    */
174   public void destruct()
175   {
176     if(null != m_dtm)
177     {
178       // For this next check, see http://nagoya.apache.org/bugzilla/show_bug.cgi?id=7622.
179       // What happens if you don't do this this check:
180       // 1) Transform#1 creates an XRTreeFrag.  This has a reference to a DTM, that in turn 
181       //    is registered with a DTMManager.  The DTM will need to be deleted from the 
182       //    DTMManager when the XRTreeFrag is deleted.  The XRTreeFrag  also contains a 
183       //    reference to the XPathContext.
184       // 2) Transform#1 completes.  The XPathContext is reset... namely the a bunch 
185       //    of structures are reset or rebuilt, including DTMManagerDefault#m_dtms.  
186       //    BUT, the XRTreeFrags are still hanging around, waiting to unregister themselves.
187       // 3) Transform#2 starts humming along.  It builds a XRTreeFrag and installs that 
188       //    RTF DTM into DTMManagerDefault#m_dtms[2].
189       // 4) The finalizer thread wakes and decides to delete some of those old XRTreeFrags 
190       //    from Transform#1.
191       // 5) The XRTreeFrag#finalize() method references through the XPathContext, and 
192       //    deletes what it thinks is it's DTM from  DTMManagerDefault#m_dtms[2] (via 
193       //    getDTMIdentity(dtm)).
194       // 6) Transform#2 tries to reference DTMManagerDefault#m_dtms[2], finds it is 
195       //    null, and chaos results.
196       int ident = m_xctxt.getDTMIdentity(m_dtm);
197       DTM foundDTM = m_xctxt.getDTM(ident);      
198       if(foundDTM == m_dtm)
199       {
200         m_xctxt.release(m_dtm, true);
201         m_dtm = null;
202         m_xctxt = null;
203       }
204     }
205     m_obj = null;
206  }
207 
208   /**
209    * Tell what kind of class this is.
210    *
211    * @return type CLASS_RTREEFRAG 
212    */
213   public int getType()
214   {
215     return CLASS_RTREEFRAG;
216   }
217 
218   /**
219    * Given a request type, return the equivalent string.
220    * For diagnostic purposes.
221    *
222    * @return type string "#RTREEFRAG"
223    */
224   public String   getTypeString()
225   {
226     return "#RTREEFRAG";
227   }
228 
229   /**
230    * Cast result object to a number.
231    *
232    * @return The result tree fragment as a number or NaN
233    */
234   public double num()
235     throws javax.xml.transform.TransformerException  
236   {
237 
238     XMLString s = xstr();
239 
240     return s.toDouble();
241   }
242 
243   /**
244    * Cast result object to a boolean.  This always returns true for a RTreeFrag
245    * because it is treated like a node-set with a single root node.
246    *
247    * @return true
248    */
249   public boolean bool()
250   {
251     return true;
252   }
253   
254   private XMLString m_xmlStr = null;
255   
256   /**
257    * Cast result object to an XMLString.
258    *
259    * @return The document fragment node data or the empty string. 
260    */
261   public XMLString xstr()
262   {
263     if(null == m_xmlStr)
264       m_xmlStr = m_dtm.getStringValue(m_dtmRoot);
265     
266     return m_xmlStr;
267   }
268   
269   /**
270    * Cast result object to a string.
271    *
272    * @return The string this wraps or the empty string if null
273    */
274   public void appendToFsb(org.apache.xml.utils.FastStringBuffer fsb)
275   {
276     XString xstring = (XString)xstr();
277     xstring.appendToFsb(fsb);
278   }
279 
280 
281   /**
282    * Cast result object to a string.
283    *
284    * @return The document fragment node data or the empty string. 
285    */
286   public String   str()
287   {
288     String   str = m_dtm.getStringValue(m_dtmRoot).toString();
289 
290     return (null == str) ? "" : str;
291   }
292 
293   /**
294    * Cast result object to a result tree fragment.
295    *
296    * @return The document fragment this wraps
297    */
298   public int rtf()
299   {
300     return m_dtmRoot;
301   }
302 
303   /**
304    * Cast result object to a DTMIterator.
305    * dml - modified to return an RTFIterator for
306    * benefit of EXSLT object-type function in 
307    * {@link org.apache.xalan.lib.ExsltCommon}.
308    * @return The document fragment as a DTMIterator
309    */
310   public DTMIterator asNodeIterator()
311   {
312     return new RTFIterator(m_dtmRoot, m_xctxt.getDTMManager());
313   }
314 
315   /**
316    * Cast result object to a nodelist. (special function).
317    *
318    * @return The document fragment as a nodelist
319    */
320   public NodeList   convertToNodeset()
321   {
322 
323     if (m_obj instanceof NodeList  )
324       return (NodeList  ) m_obj;
325     else
326       return new org.apache.xml.dtm.ref.DTMNodeList(asNodeIterator());
327   }
328 
329   /**
330    * Tell if two objects are functionally equal.
331    *
332    * @param obj2 Object to compare this to
333    *
334    * @return True if the two objects are equal
335    *
336    * @throws javax.xml.transform.TransformerException
337    */
338   public boolean equals(XObject obj2)
339   {
340 
341     try
342     {
343       if (XObject.CLASS_NODESET == obj2.getType())
344       {
345   
346         // In order to handle the 'all' semantics of 
347         // nodeset comparisons, we always call the 
348         // nodeset function.
349         return obj2.equals(this);
350       }
351       else if (XObject.CLASS_BOOLEAN == obj2.getType())
352       {
353         return bool() == obj2.bool();
354       }
355       else if (XObject.CLASS_NUMBER == obj2.getType())
356       {
357         return num() == obj2.num();
358       }
359       else if (XObject.CLASS_NODESET == obj2.getType())
360       {
361         return xstr().equals(obj2.xstr());
362       }
363       else if (XObject.CLASS_STRING == obj2.getType())
364       {
365         return xstr().equals(obj2.xstr());
366       }
367       else if (XObject.CLASS_RTREEFRAG == obj2.getType())
368       {
369   
370         // Probably not so good.  Think about this.
371         return xstr().equals(obj2.xstr());
372       }
373       else
374       {
375         return super.equals(obj2);
376       }
377     }
378     catch(javax.xml.transform.TransformerException   te)
379     {
380       throw new org.apache.xml.utils.WrappedRuntimeException(te);
381     }
382   }
383 
384 }
385
A to Z: JavaDoc & Examples Daily Java News & Articles Open Source Projects Open Source Codes Free Computer Books Remove Frame
Popular Tags