1 /*
2 * $Header$
3 * $Revision$
4 * $Date$
5 *
6 * ====================================================================
7 *
8 * Copyright 2000-2002 bob mcwhirter & James Strachan.
9 * All rights reserved.
10 *
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions are
14 * met:
15 *
16 * * Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 *
19 * * Redistributions in binary form must reproduce the above copyright
20 * notice, this list of conditions and the following disclaimer in the
21 * documentation and/or other materials provided with the distribution.
22 *
23 * * Neither the name of the Jaxen Project nor the names of its
24 * contributors may be used to endorse or promote products derived
25 * from this software without specific prior written permission.
26 *
27 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
28 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
29 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
30 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
31 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
32 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
33 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
34 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
35 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
36 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
37 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
38 *
39 * ====================================================================
40 * This software consists of voluntary contributions made by many
41 * individuals on behalf of the Jaxen Project and was originally
42 * created by bob mcwhirter <bob@werken.com> and
43 * James Strachan <jstrachan@apache.org>. For more information on the
44 * Jaxen Project, please see <http://www.jaxen.org/>.
45 *
46 * $Id$
47 */
48
49 package org.jaxen.saxpath.helpers;
50
51 import org.jaxen.saxpath.SAXPathException;
52 import org.jaxen.saxpath.XPathReader;
53
54 /** Create an {@link org.jaxen.saxpath.XPathReader} from
55 * either a system property, or a named class.
56 *
57 * <p>
58 * Similar to the SAX API, the <code>XPathReaderFactory</code>
59 * can create an <code>XPathReader</code> from a name of a
60 * class passed in directly, or by inspecting the system
61 * property <code>org.saxpath.driver</code>.
62 *
63 * @author bob mcwhirter (bob@werken.com)
64 */
65 public class XPathReaderFactory
66 {
67 /** The <code>org.saxpath.driver</code> property name. */
68 public static final String DRIVER_PROPERTY = "org.saxpath.driver";
69
70 /** The default driver to use if none is configured. */
71 protected static final String DEFAULT_DRIVER = "org.jaxen.saxpath.base.XPathReader";
72
73 private XPathReaderFactory() {}
74
75
76 /** Create an <code>XPathReader</code> using the value of
77 * the <code>org.saxpath.driver</code> system property.
78 *
79 * @return an instance of the <code>XPathReader</code> specified
80 * by the <code>org.saxpath.driver</code> property
81 *
82 * @throws SAXPathException if the property is not set, or if
83 * the class can not be instantiated for some reason,
84 * or if the class doesn't implement the <code>XPathReader</code>
85 * interface
86 */
87 public static XPathReader createReader() throws SAXPathException
88 {
89 String className = null;
90
91 try
92 {
93 className = System.getProperty( DRIVER_PROPERTY );
94 }
95 catch (SecurityException e)
96 {
97 // we'll use the default
98 }
99
100 if ( className == null
101 ||
102 className.length() == 0 )
103 {
104 className = DEFAULT_DRIVER;
105 }
106
107 return createReader( className );
108 }
109
110 /** Create an <code>XPathReader</code> using the passed
111 * in class name.
112 *
113 * @param className the name of the class that implements
114 * the <code>XPathReader</code> interface.
115 *
116 * @return an XPathReader
117 *
118 * @throws SAXPathException if the class cannot be
119 * instantiated for some reason, or if the
120 * class doesn't implement the <code>XPathReader</code>
121 * interface
122 */
123 public static XPathReader createReader(String className) throws SAXPathException
124 {
125 Class<?> readerClass = null;
126 XPathReader reader = null;
127
128 try
129 {
130 // Use the full version of Class.forName(), so as to
131 // work better in sandboxed environments, such as
132 // servlet containers and applets.
133
134 readerClass = Class.forName( className,
135 true,
136 XPathReaderFactory.class.getClassLoader() );
137
138 // Double-check that it's actually the right kind of class
139 // before attempting instantiation.
140
141 if ( ! XPathReader.class.isAssignableFrom( readerClass ) )
142 {
143 throw new SAXPathException( "Class [" + className
144 + "] does not implement the org.jaxen.saxpath.XPathReader interface." );
145 }
146 }
147 catch (ClassNotFoundException e)
148 {
149 throw new SAXPathException( e );
150 }
151
152 try
153 {
154 reader = (XPathReader) readerClass.newInstance();
155 }
156 catch (IllegalAccessException e)
157 {
158 throw new SAXPathException( e );
159 }
160 catch (InstantiationException e)
161 {
162 throw new SAXPathException( e );
163 }
164
165 return reader;
166 }
167 }