1 /*
2 * Copyright (c) 2004, 2006, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package javax.xml.datatype;
27
28 import java.io.File;
29 import java.security.AccessController;
30 import java.security.PrivilegedAction;
31 import java.util.Properties;
32 import java.util.ServiceConfigurationError;
33 import java.util.ServiceLoader;
34
35 /**
36 * <p>Implements pluggable Datatypes.</p>
37 *
38 * <p>This class is duplicated for each JAXP subpackage so keep it in sync. It
39 * is package private for secure class loading.</p>
40 *
41 * @author Santiago.PericasGeertsen@sun.com
42 */
43 class FactoryFinder {
44
45 /**
46 * Internal debug flag.
47 */
48 private static boolean debug = false;
49 /**
50 * Cache for properties in java.home/lib/jaxp.properties
51 */
52 static Properties cacheProps = new Properties();
53 /**
54 * Flag indicating if properties from java.home/lib/jaxp.properties have
55 * been cached.
56 */
57 static volatile boolean firstTime = true;
58 /**
59 * Security support class use to check access control before getting certain
60 * system resources.
61 */
62 static SecuritySupport ss = new SecuritySupport();
63
64 // Define system property "jaxp.debug" to get output
65 static {
66 // Use try/catch block to support applets, which throws
67 // SecurityException out of this code.
68 try {
69 String val = ss.getSystemProperty("jaxp.debug");
70 // Allow simply setting the prop to turn on debug
71 debug = val != null && !"false".equals(val);
72 } catch (SecurityException se) {
73 debug = false;
74 }
75 }
76
77 private static void dPrint(String msg) {
78 if (debug) {
79 System.err.println("JAXP: " + msg);
80 }
81 }
82
83 /**
84 * Attempt to load a class using the class loader supplied. If that fails
85 * and fall back is enabled, the current (i.e. bootstrap) class loader is
86 * tried.
87 *
88 * If the class loader supplied is
89 * <code>null</code>, first try using the context class loader followed by
90 * the current (i.e. bootstrap) class loader.
91 */
92 static private Class getProviderClass(String className, ClassLoader cl,
93 boolean doFallback) throws ClassNotFoundException {
94 try {
95 if (cl == null) {
96 cl = ss.getContextClassLoader();
97 if (cl == null) {
98 throw new ClassNotFoundException();
99 } else {
100 return cl.loadClass(className);
101 }
102 } else {
103 return cl.loadClass(className);
104 }
105 } catch (ClassNotFoundException e1) {
106 if (doFallback) {
107 // Use current class loader - should always be bootstrap CL
108 return Class.forName(className, true, FactoryFinder.class.getClassLoader());
109 } else {
110 throw e1;
111 }
112 }
113 }
114
115 /**
116 * Create an instance of a class. Delegates to method
117 * <code>getProviderClass()</code> in order to load the class.
118 *
119 * @param className Name of the concrete class corresponding to the service
120 * provider
121 *
122 * @param cl ClassLoader to use to load the class, null means to use the
123 * bootstrap ClassLoader
124 *
125 * @param doFallback True if the current ClassLoader should be tried as a
126 * fallback if the class is not found using cl
127 */
128 static Object newInstance(String className, ClassLoader cl, boolean doFallback)
129 throws DatatypeConfigurationException {
130 try {
131 Class providerClass = getProviderClass(className, cl, doFallback);
132 Object instance = providerClass.newInstance();
133 if (debug) { // Extra check to avoid computing cl strings
134 dPrint("created new instance of " + providerClass
135 + " using ClassLoader: " + cl);
136 }
137 return instance;
138 } catch (ClassNotFoundException x) {
139 throw new DatatypeConfigurationException(
140 "Provider " + className + " not found", x);
141 } catch (Exception x) {
142 throw new DatatypeConfigurationException(
143 "Provider " + className + " could not be instantiated: " + x,
144 x);
145 }
146 }
147
148 /**
149 * Finds the implementation Class object in the specified order. Main entry
150 * point.
151 *
152 * @return Class object of factory, never null
153 *
154 * @param factoryId Name of the factory to find, same as a property name
155 * @param fallbackClassName Implementation class name, if nothing else is
156 * found. Use null to mean no fallback.
157 *
158 * Package private so this code can be shared.
159 */
160 static Object find(Class factoryClass, String factoryId, String fallbackClassName)
161 throws DatatypeConfigurationException {
162 dPrint("find factoryId =" + factoryId);
163
164 // Use the system property first
165 try {
166 String systemProp = ss.getSystemProperty(factoryId);
167 if (systemProp != null) {
168 dPrint("found system property, value=" + systemProp);
169 return newInstance(systemProp, null, true);
170 }
171 } catch (SecurityException se) {
172 if (debug) {
173 se.printStackTrace();
174 }
175 }
176
177 // try to read from $java.home/lib/jaxp.properties
178 try {
179 String factoryClassName = null;
180 if (firstTime) {
181 synchronized (cacheProps) {
182 if (firstTime) {
183 String configFile = ss.getSystemProperty("java.home") + File.separator
184 + "lib" + File.separator + "jaxp.properties";
185 File f = new File(configFile);
186 firstTime = false;
187 if (ss.doesFileExist(f)) {
188 dPrint("Read properties file " + f);
189 cacheProps.load(ss.getFileInputStream(f));
190 }
191 }
192 }
193 }
194 factoryClassName = cacheProps.getProperty(factoryId);
195
196 if (factoryClassName != null) {
197 dPrint("found in $java.home/jaxp.properties, value=" + factoryClassName);
198 return newInstance(factoryClassName, null, true);
199 }
200 } catch (Exception ex) {
201 if (debug) {
202 ex.printStackTrace();
203 }
204 }
205
206 // Try service-provider loading facilities
207 Object provider = findServiceProvider(factoryClass, fallbackClassName);
208 if (provider != null) {
209 return provider;
210 }
211 if (fallbackClassName == null) {
212 throw new DatatypeConfigurationException(
213 "Provider for " + factoryId + " cannot be found", null);
214 }
215
216 dPrint("loaded from fallback value: " + fallbackClassName);
217 return newInstance(fallbackClassName, null, true);
218 }
219
220 /*
221 * Try to find a provider using Service Loader
222 *
223 * @return instance of provider class if found or null
224 */
225 private static Object findServiceProvider(final Class factoryClass, final String fallbackClassName)
226 throws DatatypeConfigurationException {
227 try {
228 return AccessController.doPrivileged(new PrivilegedAction() {
229 public Object run() {
230 Object defaultProvider = null;
231 for (Object factory : ServiceLoader.load(factoryClass)) {
232 if (factory.getClass().getName().equals(fallbackClassName)) {
233 defaultProvider = factory;
234 } else {
235 return factory;
236 }
237 }
238 if (defaultProvider != null) {
239 return defaultProvider;
240 }
241 return null;
242 }
243 });
244 } catch (ServiceConfigurationError e) {
245 throw new DatatypeConfigurationException(e.getMessage(), e.getCause());
246 }
247 }
248 }