1 /* XsltFilter.java --
2    Copyright (C) 2001 Free Software Foundation, Inc.
3 
4 This file is part of GNU Classpath.
5 
6 GNU Classpath is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2, or (at your option)
9 any later version.
10 
11 GNU Classpath is distributed in the hope that it will be useful, but
12 WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14 General Public License for more details.
15 
16 You should have received a copy of the GNU General Public License
17 along with GNU Classpath; see the file COPYING.  If not, write to the
18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
19 02110-1301 USA.
20 
21 Linking this library statically or dynamically with other modules is
22 making a combined work based on this library.  Thus, the terms and
23 conditions of the GNU General Public License cover the whole
24 combination.
25 
26 As a special exception, the copyright holders of this library give you
27 permission to link this library with independent modules to produce an
28 executable, regardless of the license terms of these independent
29 modules, and to copy and distribute the resulting executable under
30 terms of your choice, provided that you also meet, for each linked
31 independent module, the terms and conditions of the license of that
32 module.  An independent module is a module which is not derived from
33 or based on this library.  If you modify this library, you may extend
34 this exception to your version of the library, but you are not
35 obligated to do so.  If you do not wish to do so, delete this
36 exception statement from your version. */
37 
38 package gnu.xml.pipeline;
39 
40 import java.io.IOException;
41 
42 import javax.xml.transform.TransformerFactory;
43 import javax.xml.transform.TransformerConfigurationException;
44 import javax.xml.transform.sax.*;
45 import javax.xml.transform.stream.StreamSource;
46 
47 import org.xml.sax.SAXException;
48 import org.xml.sax.ext.LexicalHandler;
49 
50 
51 /**
52  * Packages an XSLT transform as a pipeline component.
53  * Note that all DTD events (callbacks to DeclHandler and DTDHandler
54  * interfaces) are discarded, although XSLT transforms may be set up to
55  * use the LexicalHandler to write DTDs with only an external subset.
56  * Not every XSLT engine will necessarily be usable with this filter,
57  * but current versions of
58  * <a href="http://saxon.sourceforge.net">SAXON</a> and
59  * <a href="http://xml.apache.org/xalan-j">Xalan</a> should work well.
60  *
61  * @see TransformerFactory
62  *
63  * @author David Brownell
64  */
65 final public class XsltFilter extends EventFilter
66 {
67     /**
68      * Creates a filter that performs the specified transform.
69      * Uses the JAXP 1.1 interfaces to access the default XSLT
70      * engine configured for in the current execution context,
71      * and parses the stylesheet without custom EntityResolver
72      * or ErrorHandler support.
73      *
74      * @param stylesheet URI for the stylesheet specifying the
75      *  XSLT transform
76      * @param next provides the ContentHandler and LexicalHandler
77      *  to receive XSLT output.
78      * @exception SAXException if the stylesheet can't be parsed
79      * @exception IOException if there are difficulties
80      *  bootstrapping the XSLT engine, such as it not supporting
81      *  SAX well enough to use this way.
82      */
XsltFilter(String stylesheet, EventConsumer next)83     public XsltFilter (String stylesheet, EventConsumer next)
84     throws SAXException, IOException
85     {
86         // First, get a transformer with the stylesheet preloaded
87         TransformerFactory      tf = null;
88         TransformerHandler      th;
89 
90         try {
91             SAXTransformerFactory       stf;
92 
93             tf = TransformerFactory.newInstance ();
94             if (!tf.getFeature (SAXTransformerFactory.FEATURE)  // sax inputs
95                     || !tf.getFeature (SAXResult.FEATURE)       // sax outputs
96                     || !tf.getFeature (StreamSource.FEATURE)    // stylesheet
97                     )
98                 throw new IOException ("XSLT factory ("
99                     + tf.getClass ().getName ()
100                     + ") does not support SAX");
101             stf = (SAXTransformerFactory) tf;
102             th = stf.newTransformerHandler (new StreamSource (stylesheet));
103         } catch (TransformerConfigurationException e) {
104             throw new IOException ("XSLT factory ("
105                 + (tf == null
106                         ? "none available"
107                         : tf.getClass ().getName ())
108                 + ") configuration error, "
109                 + e.getMessage ()
110                 );
111         }
112 
113         // Hook its outputs up to the pipeline ...
114         SAXResult               out = new SAXResult ();
115 
116         out.setHandler (next.getContentHandler ());
117         try {
118             LexicalHandler      lh;
119             lh = (LexicalHandler) next.getProperty (LEXICAL_HANDLER);
120             out.setLexicalHandler (lh);
121         } catch (Exception e) {
122             // ignore
123         }
124         th.setResult (out);
125 
126         // ... and make sure its inputs look like ours.
127         setContentHandler (th);
128         setProperty (LEXICAL_HANDLER, th);
129     }
130 }
131