DataFormatFilter


1   /*-- 
2   
3    Copyright (C) 2000 Brett McLaughlin & Jason Hunter.
4    All rights reserved.
5    
6    Redistribution and use in source and binary forms, with or without
7    modification, are permitted provided that the following conditions
8    are met:
9    
10   1. Redistributions of source code must retain the above copyright
11      notice, this list of conditions, and the following disclaimer.
12   
13   2. Redistributions in binary form must reproduce the above copyright
14      notice, this list of conditions, and the disclaimer that follows 
15      these conditions in the documentation and/or other materials 
16      provided with the distribution.
17  
18   3. The name "JDOM" must not be used to endorse or promote products
19      derived from this software without prior written permission.  For
20      written permission, please contact license@jdom.org.
21   
22   4. Products derived from this software may not be called "JDOM", nor
23      may "JDOM" appear in their name, without prior written permission
24      from the JDOM Project Management (pm@jdom.org).
25   
26   In addition, we request (but do not require) that you include in the 
27   end-user documentation provided with the redistribution and/or in the 
28   software itself an acknowledgement equivalent to the following:
29       "This product includes software developed by the
30        JDOM Project (http://www.jdom.org/)."
31   Alternatively, the acknowledgment may be graphical using the logos 
32   available at http://www.jdom.org/images/logos.
33  
34   THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
35   WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
36   OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
37   DISCLAIMED.  IN NO EVENT SHALL THE JDOM AUTHORS OR THE PROJECT
38   CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
39   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
40   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
41   USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
42   ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
43   OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
44   OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
45   SUCH DAMAGE.
46  
47   This software consists of voluntary contributions made by many 
48   individuals on behalf of the JDOM Project and was originally 
49   created by Brett McLaughlin <brett@jdom.org> and 
50   Jason Hunter <jhunter@jdom.org>.  For more information on the 
51   JDOM Project, please see <http://www.jdom.org/>.
52   
53   */
54  package sax;
55  
56  import java.util.Stack  ;
57  
58  import org.xml.sax.Attributes  ;
59  import org.xml.sax.SAXException  ;
60  import org.xml.sax.XMLReader  ;
61  
62  
63  /**
64   * Filter for data- or field-oriented XML.
65   *
66   * <i>Code and comments adapted from DataWriter-0.2, written
67   * by David Megginson and released into the public domain,
68   * without warranty.</i>
69   *
70   * <p>This filter adds indentation and newlines to field-oriented
71   * XML without mixed content.  All added indentation and newlines
72   * will be passed on down the filter chain.</p>
73   *
74   * <p>In general, all whitespace in an XML document is potentially
75   * significant.  There is, however, a large class of XML documents
76   * where information is strictly fielded: each element contains either
77   * character data or other elements, but not both.  For this special
78   * case, it is possible for a filter to provide automatic indentation
79   * and newlines. Note that this class will likely not yield appropriate
80   * results for document-oriented XML like XHTML pages, which mix character
81   * data and elements together.</p>
82   *
83   * <p>This filter will automatically place each start tag on a new line,
84   * optionally indented if an indent step is provided (by default, there
85   * is no indentation).  If an element contains other elements, the end
86   * tag will also appear on a new line with leading indentation.  Consider,
87   * for example, the following code:</p>
88   *
89   * <pre>
90   * DataFormatFilter df = new DataFormatFilter();
91   * df.setContentHandler(new XMLWriter());
92   *
93   * df.setIndentStep(2);
94   * df.startDocument();
95   * df.startElement("Person");
96   * df.dataElement("name", "Jane Smith");
97   * df.dataElement("date-of-birth", "1965-05-23");
98   * df.dataElement("citizenship", "US");
99   * df.endElement("Person");
100  * df.endDocument();
101  * </pre>
102  *
103  * <p>This code will produce the following document:</p>
104  *
105  * <pre>
106  * &lt;?xml version="1.0"?>
107  *
108  * &lt;Person>
109  *   &lt;name>Jane Smith&lt;/name>
110  *   &lt;date-of-birth>1965-05-23&lt;/date-of-birth>
111  *   &lt;citizenship>US&lt;/citizenship>
112  * &lt;/Person>
113  * </pre>
114  * 
115  * @see DataUnformatFilter
116  */
117 public class DataFormatFilter extends XMLFilterBase
118 {
119     
120     
121     
122     ////////////////////////////////////////////////////////////////////
123     // Constructors.
124     ////////////////////////////////////////////////////////////////////
125     
126     
127     /**
128      * Create a new filter.
129      */
130     public DataFormatFilter()
131     {
132     }
133 
134 
135     /**
136      * Create a new filter.
137      *
138      * <p>Use the XMLReader provided as the source of events.</p>
139      *
140      * @param xmlreader The parent in the filter chain.
141      */
142     public DataFormatFilter(XMLReader   xmlreader)
143     {
144         super(xmlreader);
145     }
146 
147 
148     ////////////////////////////////////////////////////////////////////
149     // Accessors and setters.
150     ////////////////////////////////////////////////////////////////////
151 
152 
153     /**
154      * Return the current indent step.
155      *
156      * <p>Return the current indent step: each start tag will be
157      * indented by this number of spaces times the number of
158      * ancestors that the element has.</p>
159      *
160      * @return The number of spaces in each indentation step,
161      *         or 0 or less for no indentation.
162      * @see #setIndentStep
163      */
164     public int getIndentStep ()
165     {
166         return indentStep;
167     }
168 
169 
170     /**
171      * Set the current indent step.
172      *
173      * @param indentStep The new indent step (0 or less for no
174      *        indentation).
175      * @see #getIndentStep
176      */
177     public void setIndentStep (int indentStep)
178     {
179         this.indentStep = indentStep;
180     }
181     
182     
183     
184     ////////////////////////////////////////////////////////////////////
185     // Public methods.
186     ////////////////////////////////////////////////////////////////////
187 
188 
189     /**
190      * Reset the filter so that it can be reused.
191      *
192      * <p>This method is especially useful if the filter failed
193      * with an exception the last time through.</p>
194      */
195     public void reset ()
196     {
197         state = SEEN_NOTHING;
198         stateStack = new Stack  ();
199     }
200 
201 
202 
203     ////////////////////////////////////////////////////////////////////
204     // Methods from org.xml.sax.ContentHandler.
205     ////////////////////////////////////////////////////////////////////
206 
207     
208     /**
209      * Filter a start document event. 
210      *
211      * <p>Reset state and pass the event on for further processing.</p>
212      *
213      * @exception org.xml.sax.SAXException If a filter
214      *            further down the chain raises an exception.
215      * @see org.xml.sax.ContentHandler#startDocument
216      */
217     public void startDocument ()
218     throws SAXException  
219     {
220         reset();
221         super.startDocument();
222     }
223 
224 
225     /**
226      * Add newline and indentation prior to start tag.
227      *
228      * <p>Each tag will begin on a new line, and will be
229      * indented by the current indent step times the number
230      * of ancestors that the element has.</p>
231      *
232      * <p>The newline and indentation will be passed on down
233      * the filter chain through regular characters events.</p>
234      *
235      * @param uri The element's Namespace URI.
236      * @param localName The element's local name.
237      * @param qName The element's qualified (prefixed) name.
238      * @param atts The element's attribute list.
239      * @exception org.xml.sax.SAXException If a filter
240      *            further down the chain raises an exception.
241      * @see org.xml.sax.ContentHandler#startElement
242      */
243     public void startElement (String   uri, String   localName,
244                               String   qName, Attributes   atts)
245     throws SAXException  
246     {
247         if (!stateStack.empty()) {
248             doNewline();
249             doIndent();
250         }
251         stateStack.push(SEEN_ELEMENT);
252         state = SEEN_NOTHING;
253         super.startElement(uri, localName, qName, atts);
254     }
255 
256 
257     /**
258      * Add newline and indentation prior to end tag.
259      *
260      * <p>If the element has contained other elements, the tag
261      * will appear indented on a new line; otherwise, it will
262      * appear immediately following whatever came before.</p>
263      *
264      * <p>The newline and indentation will be passed on down
265      * the filter chain through regular characters events.</p>
266      *
267      * @param uri The element's Namespace URI.
268      * @param localName The element's local name.
269      * @param qName The element's qualified (prefixed) name.
270      * @exception org.xml.sax.SAXException If a filter
271      *            further down the chain raises an exception.
272      * @see org.xml.sax.ContentHandler#endElement
273      */
274     public void endElement (String   uri, String   localName, String   qName)
275     throws SAXException  
276     {
277         boolean seenElement = (state == SEEN_ELEMENT);
278         state = stateStack.pop();
279         if (seenElement) {
280             doNewline();
281             doIndent();
282         }
283         super.endElement(uri, localName, qName);
284     }
285 
286 
287     /**
288      * Filter a character data event.
289      *
290      * @param ch The characters to write.
291      * @param start The starting position in the array.
292      * @param length The number of characters to use.
293      * @exception org.xml.sax.SAXException If a filter
294      *            further down the chain raises an exception.
295      * @see org.xml.sax.ContentHandler#characters
296      */
297     public void characters (char ch[], int start, int length)
298     throws SAXException  
299     {
300         state = SEEN_DATA;
301         super.characters(ch, start, length);
302     }
303     
304 
305 
306     ////////////////////////////////////////////////////////////////////
307     // Internal methods.
308     ////////////////////////////////////////////////////////////////////
309 
310 
311     /**
312      * Add newline.
313      *
314      * @exception org.xml.sax.SAXException If a filter
315      *            further down the chain raises an exception.
316      */
317     private void doNewline ()
318     throws SAXException  
319     {
320         super.characters(NEWLINE, 0, NEWLINE.length);
321     }
322 
323 
324     /**
325      * Add indentation for the current level.
326      *
327      * @exception org.xml.sax.SAXException If a filter
328      *            further down the chain raises an exception.
329      */
330     private void doIndent ()
331     throws SAXException  
332     {
333         int n = indentStep * stateStack.size();
334         if (n > 0) {
335             char ch[] = new char[n];
336             for (int i = 0; i < n; i++) {
337                 ch[i] = INDENT_CHAR;
338             }
339             super.characters(ch, 0, n);
340         }
341     }
342 
343 
344 
345 
346     ////////////////////////////////////////////////////////////////////
347     // Constants.
348     ////////////////////////////////////////////////////////////////////
349 
350     private static final Object   SEEN_NOTHING = new Object  ();
351     private static final Object   SEEN_ELEMENT = new Object  ();
352     private static final Object   SEEN_DATA = new Object  ();
353 
354     private static final char[] NEWLINE = new char[] {'\n'};
355     private static final char INDENT_CHAR = ' ';
356     
357     
358     ////////////////////////////////////////////////////////////////////
359     // Internal state.
360     ////////////////////////////////////////////////////////////////////
361 
362     private Object   state = SEEN_NOTHING;
363     private Stack   stateStack = new Stack  ();
364 
365     private int indentStep = 0;
366 
367 }
368 
369 // end of DataFormatFilter.java
370
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