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.InputStream;
29 import java.io.IOException;
30 import java.io.File;
31 import java.io.FileInputStream;
32
33 import java.util.Properties;
34 import java.io.BufferedReader;
35 import java.io.InputStreamReader;
36
37 /**
38 * <p>Implements pluggable Datatypes.</p>
39 *
40 * <p>This class is duplicated for each JAXP subpackage so keep it in
41 * sync. It is package private for secure class loading.</p>
42 *
43 * @author Santiago.PericasGeertsen@sun.com
44 */
45 class FactoryFinder {
46
47 /**
48 * Internal debug flag.
49 */
50 private static boolean debug = false;
51
52 /**
53 * Cache for properties in java.home/lib/jaxp.properties
54 */
55 static Properties cacheProps = new Properties();
56
57 /**
58 * Flag indicating if properties from java.home/lib/jaxp.properties
59 * have been cached.
60 */
61 static volatile boolean firstTime = true;
62
63 /**
64 * Security support class use to check access control before
65 * getting certain system resources.
66 */
67 static SecuritySupport ss = new SecuritySupport();
68
69 // Define system property "jaxp.debug" to get output
70 static {
71 // Use try/catch block to support applets, which throws
72 // SecurityException out of this code.
73 try {
74 String val = ss.getSystemProperty("jaxp.debug");
75 // Allow simply setting the prop to turn on debug
76 debug = val != null && !"false".equals(val);
77 }
78 catch (SecurityException se) {
79 debug = false;
80 }
81 }
82
83 private static void dPrint(String msg) {
84 if (debug) {
85 System.err.println("JAXP: " + msg);
86 }
87 }
88
89 /**
90 * Attempt to load a class using the class loader supplied. If that fails
91 * and fall back is enabled, the current (i.e. bootstrap) class loader is
92 * tried.
93 *
94 * If the class loader supplied is <code>null</code>, first try using the
95 * context class loader followed by the current (i.e. bootstrap) class
96 * loader.
97 */
98 static private Class getProviderClass(String className, ClassLoader cl,
99 boolean doFallback) throws ClassNotFoundException
100 {
101 try {
102 if (cl == null) {
103 cl = ss.getContextClassLoader();
104 if (cl == null) {
105 throw new ClassNotFoundException();
106 }
107 else {
108 return cl.loadClass(className);
109 }
110 }
111 else {
112 return cl.loadClass(className);
113 }
114 }
115 catch (ClassNotFoundException e1) {
116 if (doFallback) {
117 // Use current class loader - should always be bootstrap CL
118 return Class.forName(className, true, FactoryFinder.class.getClassLoader());
119 }
120 else {
121 throw e1;
122 }
123 }
124 }
125
126 /**
127 * Create an instance of a class. Delegates to method
128 * <code>getProviderClass()</code> in order to load the class.
129 *
130 * @param className Name of the concrete class corresponding to the
131 * service provider
132 *
133 * @param cl ClassLoader to use to load the class, null means to use
134 * the bootstrap ClassLoader
135 *
136 * @param doFallback True if the current ClassLoader should be tried as
137 * a fallback if the class is not found using cl
138 */
139 static Object newInstance(String className, ClassLoader cl, boolean doFallback)
140 throws ConfigurationError
141 {
142 try {
143 Class providerClass = getProviderClass(className, cl, doFallback);
144 Object instance = providerClass.newInstance();
145 if (debug) { // Extra check to avoid computing cl strings
146 dPrint("created new instance of " + providerClass +
147 " using ClassLoader: " + cl);
148 }
149 return instance;
150 }
151 catch (ClassNotFoundException x) {
152 throw new ConfigurationError(
153 "Provider " + className + " not found", x);
154 }
155 catch (Exception x) {
156 throw new ConfigurationError(
157 "Provider " + className + " could not be instantiated: " + x,
158 x);
159 }
160 }
161
162 /**
163 * Finds the implementation Class object in the specified order.
164 *
165 * @return Class object of factory, never null
166 *
167 * @param factoryId Name of the factory to find, same as
168 * a property name
169 * @param fallbackClassName Implementation class name, if nothing else
170 * is found. Use null to mean no fallback.
171 *
172 * Package private so this code can be shared.
173 */
174 static Object find(String factoryId, String fallbackClassName)
175 throws ConfigurationError
176 {
177 return find(factoryId, null, fallbackClassName);
178 }
179
180 /**
181 * Finds the implementation Class object in the specified order. Main
182 * entry point.
183 * @return Class object of factory, never null
184 *
185 * @param factoryId Name of the factory to find, same as
186 * a property name
187 *
188 * @param cl ClassLoader to be used to load the class, null means to use
189 * the bootstrap ClassLoader
190 *
191 * @param fallbackClassName Implementation class name, if nothing else
192 * is found. Use null to mean no fallback.
193 *
194 * Package private so this code can be shared.
195 */
196 static Object find(String factoryId, ClassLoader cl, String fallbackClassName)
197 throws ConfigurationError
198 {
199 dPrint("find factoryId =" + factoryId);
200
201 // Use the system property first
202 try {
203 String systemProp = ss.getSystemProperty(factoryId);
204 if (systemProp != null) {
205 dPrint("found system property, value=" + systemProp);
206 return newInstance(systemProp, null, true);
207 }
208 }
209 catch (SecurityException se) {
210 if (debug) se.printStackTrace();
211 }
212
213 // Try read $java.home/lib/stax.properties followed by
214 // $java.home/lib/jaxp.properties if former not present
215 String configFile = null;
216 try {
217 String factoryClassName = null;
218 if (firstTime) {
219 synchronized (cacheProps) {
220 if (firstTime) {
221 configFile = ss.getSystemProperty("java.home") + File.separator +
222 "lib" + File.separator + "stax.properties";
223 File f = new File(configFile);
224 firstTime = false;
225 if (ss.doesFileExist(f)) {
226 dPrint("Read properties file "+f);
227 cacheProps.load(ss.getFileInputStream(f));
228 }
229 else {
230 configFile = ss.getSystemProperty("java.home") + File.separator +
231 "lib" + File.separator + "jaxp.properties";
232 f = new File(configFile);
233 if (ss.doesFileExist(f)) {
234 dPrint("Read properties file "+f);
235 cacheProps.load(ss.getFileInputStream(f));
236 }
237 }
238 }
239 }
240 }
241 factoryClassName = cacheProps.getProperty(factoryId);
242
243 if (factoryClassName != null) {
244 dPrint("found in " + configFile + " value=" + factoryClassName);
245 return newInstance(factoryClassName, null, true);
246 }
247 }
248 catch (Exception ex) {
249 if (debug) ex.printStackTrace();
250 }
251
252 // Try Jar Service Provider Mechanism
253 Object provider = findJarServiceProvider(factoryId);
254 if (provider != null) {
255 return provider;
256 }
257 if (fallbackClassName == null) {
258 throw new ConfigurationError(
259 "Provider for " + factoryId + " cannot be found", null);
260 }
261
262 dPrint("loaded from fallback value: " + fallbackClassName);
263 return newInstance(fallbackClassName, cl, true);
264 }
265
266 /*
267 * Try to find provider using Jar Service Provider Mechanism
268 *
269 * @return instance of provider class if found or null
270 */
271 private static Object findJarServiceProvider(String factoryId)
272 throws ConfigurationError
273 {
274 String serviceId = "META-INF/services/" + factoryId;
275 InputStream is = null;
276
277 // First try the Context ClassLoader
278 ClassLoader cl = ss.getContextClassLoader();
279 if (cl != null) {
280 is = ss.getResourceAsStream(cl, serviceId);
281
282 // If no provider found then try the current ClassLoader
283 if (is == null) {
284 cl = FactoryFinder.class.getClassLoader();
285 is = ss.getResourceAsStream(cl, serviceId);
286 }
287 } else {
288 // No Context ClassLoader, try the current ClassLoader
289 cl = FactoryFinder.class.getClassLoader();
290 is = ss.getResourceAsStream(cl, serviceId);
291 }
292
293 if (is == null) {
294 // No provider found
295 return null;
296 }
297
298 if (debug) { // Extra check to avoid computing cl strings
299 dPrint("found jar resource=" + serviceId + " using ClassLoader: " + cl);
300 }
301
302 BufferedReader rd;
303 try {
304 rd = new BufferedReader(new InputStreamReader(is, "UTF-8"));
305 }
306 catch (java.io.UnsupportedEncodingException e) {
307 rd = new BufferedReader(new InputStreamReader(is));
308 }
309
310 String factoryClassName = null;
311 try {
312 // XXX Does not handle all possible input as specified by the
313 // Jar Service Provider specification
314 factoryClassName = rd.readLine();
315 rd.close();
316 } catch (IOException x) {
317 // No provider found
318 return null;
319 }
320
321 if (factoryClassName != null && !"".equals(factoryClassName)) {
322 dPrint("found in resource, value=" + factoryClassName);
323
324 // Note: here we do not want to fall back to the current
325 // ClassLoader because we want to avoid the case where the
326 // resource file was found using one ClassLoader and the
327 // provider class was instantiated using a different one.
328 return newInstance(factoryClassName, cl, false);
329 }
330
331 // No provider found
332 return null;
333 }
334
335 static class ConfigurationError extends Error {
336 private Exception exception;
337
338 /**
339 * Construct a new instance with the specified detail string and
340 * exception.
341 */
342 ConfigurationError(String msg, Exception x) {
343 super(msg);
344 this.exception = x;
345 }
346
347 Exception getException() {
348 return exception;
349 }
350 /**
351 * use the exception chaining mechanism of JDK1.4
352 */
353 @Override
354 public Throwable getCause() {
355 return exception;
356 }
357 }
358
359 }