1 package org.apache.torque.engine.database.transform;
2
3 /*
4 * Licensed to the Apache Software Foundation (ASF) under one
5 * or more contributor license agreements. See the NOTICE file
6 * distributed with this work for additional information
7 * regarding copyright ownership. The ASF licenses this file
8 * to you under the Apache License, Version 2.0 (the
9 * "License"); you may not use this file except in compliance
10 * with the License. You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing,
15 * software distributed under the License is distributed on an
16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17 * KIND, either express or implied. See the License for the
18 * specific language governing permissions and limitations
19 * under the License.
20 */
21
22 import java.io.IOException;
23 import java.io.InputStream;
24
25 import org.apache.commons.logging.Log;
26 import org.apache.commons.logging.LogFactory;
27 import org.xml.sax.EntityResolver;
28 import org.xml.sax.InputSource;
29 import org.xml.sax.SAXException;
30
31 /**
32 * A resolver to get the database.dtd file for the XML parser from the jar.
33 *
34 * @author <a href="mailto:mpoeschl@marmot.at">Martin Poeschl</a>
35 * @author <a href="mailto:kschrader@karmalab.org">Kurt Schrader</a>
36 * @author <a href="mailto:quintonm@bellsouth.net">Quinton McCombs</a>
37 * @version $Id: DTDResolver.java,v 1.1 2007-10-21 07:57:26 abyrne Exp $
38 */
39 public class DTDResolver implements EntityResolver
40 {
41 /** Where the DTD is located on the web. */
42 public static final String WEB_SITE_DTD
43 = "http://db.apache.org/torque/dtd/database_3_3.dtd";
44
45 /** Where the 3.2 DTD is located on the web. */
46 public static final String WEB_SITE_DTD_3_2
47 = "http://db.apache.org/torque/dtd/database_3_2.dtd";
48
49 /** Logging class from commons.logging */
50 private static Log log = LogFactory.getLog(DTDResolver.class);
51
52 /**
53 * constructor
54 */
55 public DTDResolver()
56 throws SAXException
57 {
58 }
59
60 /**
61 * An implementation of the SAX <code>EntityResolver</code>
62 * interface to be called by the XML parser. If the dtd is the
63 * current Torque DTD, the DTD is read from the generator jar.
64 * In all other cases, null is returned to indicate that the parser
65 * should open a regular connection to the systemId URI.
66 *
67 * @param publicId The public identifier of the external entity
68 * @param systemId The system identifier of the external entity
69 * @return An <code>InputSource</code> for the
70 * <code>database.dtd</code> file in the generator jar, or null.
71 */
72 public InputSource resolveEntity(String publicId, String systemId)
73 throws IOException, SAXException
74 {
75 if (WEB_SITE_DTD.equals(systemId))
76 {
77 return readFromClasspath("database.dtd");
78 }
79 else if (WEB_SITE_DTD_3_2.equals(systemId))
80 {
81 return readFromClasspath("database_3_2.dtd");
82 }
83 else
84 {
85 log.debug("Resolver: used default behaviour");
86 return null;
87 }
88 }
89
90 /**
91 * Reads the resource with the given name from the classpath.
92 *
93 * @param resourceName the name of the resource to read
94 * @return an Inputsource witht the content of the resource.
95 *
96 * @throws SAXException if the resource cannot be read.
97 */
98 private InputSource readFromClasspath(String resourceName)
99 throws SAXException
100 {
101 try
102 {
103 InputStream dtdStream
104 = getClass().getResourceAsStream(resourceName);
105
106 // getResource was buggy on many systems including Linux,
107 // OSX, and some versions of windows in jdk1.3.
108 // getResourceAsStream works on linux, maybe others?
109 if (dtdStream != null)
110 {
111 String pkg = getClass().getName().substring(0,
112 getClass().getName().lastIndexOf('.'));
113 log.debug("Resolver: used " + resourceName + " from '"
114 + pkg + "' package");
115 return new InputSource(dtdStream);
116 }
117 else
118 {
119 log.warn("Could not locate database.dtd");
120 return null;
121 }
122 }
123 catch (Exception ex)
124 {
125 throw new SAXException(
126 "Could not get stream for " + resourceName,
127 ex);
128 }
129 }
130 }