1 /*
2 * Copyright (c) 2005, 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.stream;
27
28 import java.io.File;
29 import java.security.AccessController;
30 import java.security.PrivilegedAction;
31 import java.util.Iterator;
32 import java.util.Properties;
33 import java.util.ServiceConfigurationError;
34 import java.util.ServiceLoader;
35
36 /**
37 * <p>Implements pluggable Datatypes.</p>
38 *
39 * <p>This class is duplicated for each JAXP subpackage so keep it in
40 * sync. It is package private for secure class loading.</p>
41 *
42 * @author Santiago.PericasGeertsen@sun.com
43 */
44 class FactoryFinder {
45
46 /**
47 * Internal debug flag.
48 */
49 private static boolean debug = false;
50
51 /**
52 * Cache for properties in java.home/lib/jaxp.properties
53 */
54 final private static Properties cacheProps = new Properties();
55
56 /**
57 * Flag indicating if properties from java.home/lib/jaxp.properties
58 * have been cached.
59 */
60 private static volatile boolean firstTime = true;
61
62 /**
63 * Security support class use to check access control before
64 * getting certain system resources.
65 */
66 final private static SecuritySupport ss = new SecuritySupport();
67
68 // Define system property "jaxp.debug" to get output
69 static {
70 // Use try/catch block to support applets, which throws
71 // SecurityException out of this code.
72 try {
73 String val = ss.getSystemProperty("jaxp.debug");
74 // Allow simply setting the prop to turn on debug
75 debug = val != null && !"false".equals(val);
76 }
77 catch (SecurityException se) {
78 debug = false;
79 }
80 }
81
82 private static void dPrint(String msg) {
83 if (debug) {
84 System.err.println("JAXP: " + msg);
85 }
86 }
87
88 /**
89 * Attempt to load a class using the class loader supplied. If that fails
90 * and fall back is enabled, the current (i.e. bootstrap) class loader is
91 * tried.
92 *
93 * If the class loader supplied is <code>null</code>, first try using the
94 * context class loader followed by the current (i.e. bootstrap) class
95 * loader.
96 */
97 static private Class getProviderClass(String className, ClassLoader cl,
98 boolean doFallback) throws ClassNotFoundException
99 {
100 try {
101 if (cl == null) {
102 cl = ss.getContextClassLoader();
103 if (cl == null) {
104 throw new ClassNotFoundException();
105 }
106 else {
107 return Class.forName(className, false, cl);
108 }
109 }
110 else {
111 return Class.forName(className, false, cl);
112 }
113 }
114 catch (ClassNotFoundException e1) {
115 if (doFallback) {
116 // Use current class loader - should always be bootstrap CL
117 return Class.forName(className, false, FactoryFinder.class.getClassLoader());
118 }
119 else {
120 throw e1;
121 }
122 }
123 }
124
125 /**
126 * Create an instance of a class. Delegates to method
127 * <code>getProviderClass()</code> in order to load the class.
128 *
129 * @param type Base class / Service interface of the factory to
130 * instantiate.
131 *
132 * @param className Name of the concrete class corresponding to the
133 * service provider
134 *
135 * @param cl ClassLoader to use to load the class, null means to use
136 * the bootstrap ClassLoader
137 *
138 * @param doFallback True if the current ClassLoader should be tried as
139 * a fallback if the class is not found using cl
140 */
141 static <T> T newInstance(Class<T> type, String className, ClassLoader cl,
142 boolean doFallback)
143 throws FactoryConfigurationError
144 {
145 assert type != null;
146 try {
147 Class<?> providerClass = getProviderClass(className, cl, doFallback);
148 if (!type.isAssignableFrom(providerClass)) {
149 throw new ClassCastException(className + " cannot be cast to " + type.getName());
150 }
151 Object instance = providerClass.newInstance();
152 if (debug) { // Extra check to avoid computing cl strings
153 dPrint("created new instance of " + providerClass +
154 " using ClassLoader: " + cl);
155 }
156 return type.cast(instance);
157 }
158 catch (ClassNotFoundException x) {
159 throw new FactoryConfigurationError(
160 "Provider " + className + " not found", x);
161 }
162 catch (Exception x) {
163 throw new FactoryConfigurationError(
164 "Provider " + className + " could not be instantiated: " + x,
165 x);
166 }
167 }
168
169 /**
170 * Finds the implementation Class object in the specified order.
171 *
172 * @return Class object of factory, never null
173 *
174 * @param type Base class / Service interface of the
175 * factory to find.
176 *
177 * @param fallbackClassName Implementation class name, if nothing else
178 * is found. Use null to mean no fallback.
179 *
180 * Package private so this code can be shared.
181 */
182 static <T> T find(Class<T> type, String fallbackClassName)
183 throws FactoryConfigurationError
184 {
185 return find(type, type.getName(), null, fallbackClassName);
186 }
187
188 /**
189 * Finds the implementation Class object in the specified order. Main
190 * entry point.
191 * @return Class object of factory, never null
192 *
193 * @param type Base class / Service interface of the
194 * factory to find.
195 *
196 * @param factoryId Name of the factory to find, same as
197 * a property name
198 *
199 * @param cl ClassLoader to be used to load the class, null means to use
200 * the bootstrap ClassLoader
201 *
202 * @param fallbackClassName Implementation class name, if nothing else
203 * is found. Use null to mean no fallback.
204 *
205 * Package private so this code can be shared.
206 */
207 static <T> T find(Class<T> type, String factoryId, ClassLoader cl, String fallbackClassName)
208 throws FactoryConfigurationError
209 {
210 dPrint("find factoryId =" + factoryId);
211
212 // Use the system property first
213 try {
214 String systemProp = ss.getSystemProperty(factoryId);
215 if (systemProp != null) {
216 dPrint("found system property, value=" + systemProp);
217 // There's a bug here - because 'cl' is ignored.
218 // This will be handled separately.
219 return newInstance(type, systemProp, null, true);
220 }
221 }
222 catch (SecurityException se) {
223 if (debug) se.printStackTrace();
224 }
225
226 // Try read $java.home/lib/stax.properties followed by
227 // $java.home/lib/jaxp.properties if former not present
228 String configFile = null;
229 try {
230 String factoryClassName;
231 if (firstTime) {
232 synchronized (cacheProps) {
233 if (firstTime) {
234 configFile = ss.getSystemProperty("java.home") + File.separator +
235 "lib" + File.separator + "stax.properties";
236 File f = new File(configFile);
237 firstTime = false;
238 if (ss.doesFileExist(f)) {
239 dPrint("Read properties file "+f);
240 cacheProps.load(ss.getFileInputStream(f));
241 }
242 else {
243 configFile = ss.getSystemProperty("java.home") + File.separator +
244 "lib" + File.separator + "jaxp.properties";
245 f = new File(configFile);
246 if (ss.doesFileExist(f)) {
247 dPrint("Read properties file "+f);
248 cacheProps.load(ss.getFileInputStream(f));
249 }
250 }
251 }
252 }
253 }
254 factoryClassName = cacheProps.getProperty(factoryId);
255
256 if (factoryClassName != null) {
257 dPrint("found in " + configFile + " value=" + factoryClassName);
258 // There's a bug here - because 'cl' is ignored.
259 // This will be handled separately.
260 return newInstance(type, factoryClassName, null, true);
261 }
262 }
263 catch (Exception ex) {
264 if (debug) ex.printStackTrace();
265 }
266
267 if (type.getName().equals(factoryId)) {
268 // Try Jar Service Provider Mechanism
269 final T provider = findServiceProvider(type);
270 if (provider != null) {
271 return provider;
272 }
273 } else {
274 // We're in the case where a 'custom' factoryId was provided,
275 // and in every case where that happens, we expect that
276 // fallbackClassName will be null.
277 assert fallbackClassName == null;
278 }
279
280 if (fallbackClassName == null) {
281 throw new FactoryConfigurationError(
282 "Provider for " + factoryId + " cannot be found", null);
283 }
284
285 dPrint("loaded from fallback value: " + fallbackClassName);
286 return newInstance(type, fallbackClassName, cl, true);
287 }
288
289 /*
290 * Try to find provider using the ServiceLoader API
291 *
292 * @param type Base class / Service interface of the factory to find.
293 *
294 * @return instance of provider class if found or null
295 */
296 private static <T> T findServiceProvider(final Class<T> type) {
297 try {
298 return AccessController.doPrivileged(new PrivilegedAction<T>() {
299 public T run() {
300 final ServiceLoader<T> serviceLoader = ServiceLoader.load(type);
301 final Iterator<T> iterator = serviceLoader.iterator();
302 if (iterator.hasNext()) {
303 return iterator.next();
304 } else {
305 return null;
306 }
307 }
308 });
309 } catch(ServiceConfigurationError e) {
310 // It is not possible to wrap an error directly in
311 // FactoryConfigurationError - so we need to wrap the
312 // ServiceConfigurationError in a RuntimeException.
313 // The alternative would be to modify the logic in
314 // FactoryConfigurationError to allow setting a
315 // Throwable as the cause, but that could cause
316 // compatibility issues down the road.
317 final RuntimeException x = new RuntimeException(
318 "Provider for " + type + " cannot be created", e);
319 final FactoryConfigurationError error =
320 new FactoryConfigurationError(x, x.getMessage());
321 throw error;
322 }
323 }
324
325 }