1 /*
2 * Copyright (c) 2014, 2017, 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 java.lang.module;
27
28 import java.io.File;
29 import java.io.FilePermission;
30 import java.nio.file.Files;
31 import java.nio.file.Path;
32 import java.nio.file.Paths;
33 import java.security.AccessController;
34 import java.security.Permission;
35 import java.security.PrivilegedAction;
36 import java.util.Collections;
37 import java.util.HashMap;
38 import java.util.HashSet;
39 import java.util.List;
40 import java.util.Map;
41 import java.util.Objects;
42 import java.util.Optional;
43 import java.util.Set;
44
45 import jdk.internal.module.ModulePath;
46 import jdk.internal.module.SystemModuleFinder;
47 import sun.security.action.GetPropertyAction;
48
49 /**
50 * A finder of modules. A {@code ModuleFinder} is used to find modules during
51 * <a href="package-summary.html#resolution">resolution</a> or
52 * <a href="package-summary.html#servicebinding">service binding</a>.
53 *
54 * <p> A {@code ModuleFinder} can only find one module with a given name. A
55 * {@code ModuleFinder} that finds modules in a sequence of directories, for
56 * example, will locate the first occurrence of a module of a given name and
57 * will ignore other modules of that name that appear in directories later in
58 * the sequence. </p>
59 *
60 * <p> Example usage: </p>
61 *
62 * <pre>{@code
63 * Path dir1, dir2, dir3;
64 *
65 * ModuleFinder finder = ModuleFinder.of(dir1, dir2, dir3);
66 *
67 * Optional<ModuleReference> omref = finder.find("jdk.foo");
68 * omref.ifPresent(mref -> ... );
69 *
70 * }</pre>
71 *
72 * <p> The {@link #find(String) find} and {@link #findAll() findAll} methods
73 * defined here can fail for several reasons. These include I/O errors, errors
74 * detected parsing a module descriptor ({@code module-info.class}), or in the
75 * case of {@code ModuleFinder} returned by {@link #of ModuleFinder.of}, that
76 * two or more modules with the same name are found in a directory.
77 * When an error is detected then these methods throw {@link FindException
78 * FindException} with an appropriate {@link Throwable#getCause cause}.
79 * The behavior of a {@code ModuleFinder} after a {@code FindException} is
80 * thrown is undefined. For example, invoking {@code find} after an exception
81 * is thrown may or may not scan the same modules that lead to the exception.
82 * It is recommended that a module finder be discarded after an exception is
83 * thrown. </p>
84 *
85 * <p> A {@code ModuleFinder} is not required to be thread safe. </p>
86 *
87 * @since 9
88 * @spec JPMS
89 */
90
91 public interface ModuleFinder {
92
93 /**
94 * Finds a reference to a module of a given name.
95 *
96 * <p> A {@code ModuleFinder} provides a consistent view of the
97 * modules that it locates. If {@code find} is invoked several times to
98 * locate the same module (by name) then it will return the same result
99 * each time. If a module is located then it is guaranteed to be a member
100 * of the set of modules returned by the {@link #findAll() findAll}
101 * method. </p>
102 *
103 * @param name
104 * The name of the module to find
105 *
106 * @return A reference to a module with the given name or an empty
107 * {@code Optional} if not found
108 *
109 * @throws FindException
110 * If an error occurs finding the module
111 *
112 * @throws SecurityException
113 * If denied by the security manager
114 */
115 Optional<ModuleReference> find(String name);
116
117 /**
118 * Returns the set of all module references that this finder can locate.
119 *
120 * <p> A {@code ModuleFinder} provides a consistent view of the modules
121 * that it locates. If {@link #findAll() findAll} is invoked several times
122 * then it will return the same (equals) result each time. For each {@code
123 * ModuleReference} element in the returned set then it is guaranteed that
124 * {@link #find find} will locate the {@code ModuleReference} if invoked
125 * to find that module. </p>
126 *
127 * @apiNote This is important to have for methods such as {@link
128 * Configuration#resolveAndBind resolveAndBind} that need to scan the
129 * module path to find modules that provide a specific service.
130 *
131 * @return The set of all module references that this finder locates
132 *
133 * @throws FindException
134 * If an error occurs finding all modules
135 *
136 * @throws SecurityException
137 * If denied by the security manager
138 */
139 Set<ModuleReference> findAll();
140
141 /**
142 * Returns a module finder that locates the <em>system modules</em>. The
143 * system modules are the modules in the Java run-time image.
144 * The module finder will always find {@code java.base}.
145 *
146 * <p> If there is a security manager set then its {@link
147 * SecurityManager#checkPermission(Permission) checkPermission} method is
148 * invoked to check that the caller has been granted {@link FilePermission}
149 * to recursively read the directory that is the value of the system
150 * property {@code java.home}. </p>
151 *
152 * @return A {@code ModuleFinder} that locates the system modules
153 *
154 * @throws SecurityException
155 * If denied by the security manager
156 */
157 static ModuleFinder ofSystem() {
158 String home;
159
160 SecurityManager sm = System.getSecurityManager();
161 if (sm != null) {
162 PrivilegedAction<String> pa = new GetPropertyAction("java.home");
163 home = AccessController.doPrivileged(pa);
164 Permission p = new FilePermission(home + File.separator + "-", "read");
165 sm.checkPermission(p);
166 } else {
167 home = System.getProperty("java.home");
168 }
169
170 Path modules = Paths.get(home, "lib", "modules");
171 if (Files.isRegularFile(modules)) {
172 return SystemModuleFinder.getInstance();
173 } else {
174 Path mlib = Paths.get(home, "modules");
175 if (Files.isDirectory(mlib)) {
176 return of(mlib);
177 } else {
178 throw new InternalError("Unable to detect the run-time image");
179 }
180 }
181 }
182
183 /**
184 * Returns a module finder that locates modules on the file system by
185 * searching a sequence of directories and/or packaged modules.
186 *
187 * Each element in the given array is one of:
188 * <ol>
189 * <li><p> A path to a directory of modules.</p></li>
190 * <li><p> A path to the <em>top-level</em> directory of an
191 * <em>exploded module</em>. </p></li>
192 * <li><p> A path to a <em>packaged module</em>. </p></li>
193 * </ol>
194 *
195 * The module finder locates modules by searching each directory, exploded
196 * module, or packaged module in array index order. It finds the first
197 * occurrence of a module with a given name and ignores other modules of
198 * that name that appear later in the sequence.
199 *
200 * <p> If an element is a path to a directory of modules then each entry in
201 * the directory is a packaged module or the top-level directory of an
202 * exploded module. It it an error if a directory contains more than one
203 * module with the same name. If an element is a path to a directory, and
204 * that directory contains a file named {@code module-info.class}, then the
205 * directory is treated as an exploded module rather than a directory of
206 * modules. </p>
207 *
208 * <p> The module finder returned by this method supports modules that are
209 * packaged as JAR files. A JAR file with a {@code module-info.class} in
210 * the top-level directory of the JAR file (or overridden by a versioned
211 * entry in a {@link java.util.jar.JarFile#isMultiRelease() multi-release}
212 * JAR file) is a modular JAR and is an <em>explicit module</em>.
213 * A JAR file that does not have a {@code module-info.class} in the
214 * top-level directory is created as an automatic module. The components
215 * for the automatic module are derived as follows:
216 *
217 * <ul>
218 *
219 * <li><p> The module {@link ModuleDescriptor#name() name}, and {@link
220 * ModuleDescriptor#version() version} if applicable, is derived from
221 * the file name of the JAR file as follows: </p>
222 *
223 * <ul>
224 *
225 * <li><p> The {@code .jar} suffix is removed. </p></li>
226 *
227 * <li><p> If the name matches the regular expression {@code
228 * "-(\\d+(\\.|$))"} then the module name will be derived from the
229 * subsequence preceding the hyphen of the first occurrence. The
230 * subsequence after the hyphen is parsed as a {@link
231 * ModuleDescriptor.Version} and ignored if it cannot be parsed as
232 * a {@code Version}. </p></li>
233 *
234 * <li><p> For the module name, then any trailing digits and dots
235 * are removed, all non-alphanumeric characters ({@code [^A-Za-z0-9]})
236 * are replaced with a dot ({@code "."}), all repeating dots are
237 * replaced with one dot, and all leading and trailing dots are
238 * removed. </p></li>
239 *
240 * <li><p> As an example, a JAR file named {@code foo-bar.jar} will
241 * derive a module name {@code foo.bar} and no version. A JAR file
242 * named {@code foo-1.2.3-SNAPSHOT.jar} will derive a module name
243 * {@code foo} and {@code 1.2.3-SNAPSHOT} as the version. </p></li>
244 *
245 * </ul></li>
246 *
247 * <li><p> The set of packages in the module is derived from the
248 * non-directory entries in the JAR file that have names ending in
249 * "{@code .class}". A candidate package name is derived from the name
250 * using the characters up to, but not including, the last forward slash.
251 * All remaining forward slashes are replaced with dot ({@code "."}). If
252 * the resulting string is a legal package name then it is assumed to be
253 * a package name. For example, if the JAR file contains the entry
254 * "{@code p/q/Foo.class}" then the package name derived is
255 * "{@code p.q}".</p></li>
256 *
257 * <li><p> The contents of entries starting with {@code
258 * META-INF/services/} are assumed to be service configuration files
259 * (see {@link java.util.ServiceLoader}). If the name of a file
260 * (that follows {@code META-INF/services/}) is a legal class name
261 * then it is assumed to be the fully-qualified class name of a service
262 * type. The entries in the file are assumed to be the fully-qualified
263 * class names of provider classes. </p></li>
264 *
265 * <li><p> If the JAR file has a {@code Main-Class} attribute in its
266 * main manifest then its value is the module {@link
267 * ModuleDescriptor#mainClass() main class}. </p></li>
268 *
269 * </ul>
270 *
271 * <p> If a {@code ModuleDescriptor} cannot be created (by means of the
272 * {@link ModuleDescriptor.Builder ModuleDescriptor.Builder} API) for an
273 * automatic module then {@code FindException} is thrown. This can arise
274 * when a legal module name cannot be derived from the file name of the JAR
275 * file, where the JAR file contains a {@code .class} in the top-level
276 * directory of the JAR file, where an entry in a service configuration
277 * file is not a legal class name or its package name is not in the set of
278 * packages derived for the module, or where the module main class is not
279 * a legal class name or its package is not in the module. </p>
280 *
281 * <p> In addition to JAR files, an implementation may also support modules
282 * that are packaged in other implementation specific module formats. If
283 * an element in the array specified to this method is a path to a directory
284 * of modules then entries in the directory that not recognized as modules
285 * are ignored. If an element in the array is a path to a packaged module
286 * that is not recognized then a {@code FindException} is thrown when the
287 * file is encountered. Paths to files that do not exist are always ignored.
288 * </p>
289 *
290 * <p> As with automatic modules, the contents of a packaged or exploded
291 * module may need to be <em>scanned</em> in order to determine the packages
292 * in the module. If a {@code .class} file (other than {@code
293 * module-info.class}) is found in the top-level directory then it is
294 * assumed to be a class in the unnamed package and so {@code FindException}
295 * is thrown. </p>
296 *
297 * <p> Finders created by this method are lazy and do not eagerly check
298 * that the given file paths are directories or packaged modules.
299 * Consequently, the {@code find} or {@code findAll} methods will only
300 * fail if invoking these methods results in searching a directory or
301 * packaged module and an error is encountered. </p>
302 *
303 * @param entries
304 * A possibly-empty array of paths to directories of modules
305 * or paths to packaged or exploded modules
306 *
307 * @return A {@code ModuleFinder} that locates modules on the file system
308 */
309 static ModuleFinder of(Path... entries) {
310 // special case zero entries
311 if (entries.length == 0) {
312 return new ModuleFinder() {
313 @Override
314 public Optional<ModuleReference> find(String name) {
315 Objects.requireNonNull(name);
316 return Optional.empty();
317 }
318
319 @Override
320 public Set<ModuleReference> findAll() {
321 return Collections.emptySet();
322 }
323 };
324 }
325
326 return new ModulePath(entries);
327 }
328
329 /**
330 * Returns a module finder that is composed from a sequence of zero or more
331 * module finders. The {@link #find(String) find} method of the resulting
332 * module finder will locate a module by invoking the {@code find} method
333 * of each module finder, in array index order, until either the module is
334 * found or all module finders have been searched. The {@link #findAll()
335 * findAll} method of the resulting module finder will return a set of
336 * modules that includes all modules located by the first module finder.
337 * The set of modules will include all modules located by the second or
338 * subsequent module finder that are not located by previous module finders
339 * in the sequence.
340 *
341 * <p> When locating modules then any exceptions or errors thrown by the
342 * {@code find} or {@code findAll} methods of the underlying module finders
343 * will be propagated to the caller of the resulting module finder's
344 * {@code find} or {@code findAll} methods. </p>
345 *
346 * @param finders
347 * The array of module finders
348 *
349 * @return A {@code ModuleFinder} that composes a sequence of module finders
350 */
351 static ModuleFinder compose(ModuleFinder... finders) {
352 // copy the list and check for nulls
353 final List<ModuleFinder> finderList = List.of(finders);
354
355 return new ModuleFinder() {
356 private final Map<String, ModuleReference> nameToModule = new HashMap<>();
357 private Set<ModuleReference> allModules;
358
359 @Override
360 public Optional<ModuleReference> find(String name) {
361 // cached?
362 ModuleReference mref = nameToModule.get(name);
363 if (mref != null)
364 return Optional.of(mref);
365 Optional<ModuleReference> omref = finderList.stream()
366 .map(f -> f.find(name))
367 .flatMap(Optional::stream)
368 .findFirst();
369 omref.ifPresent(m -> nameToModule.put(name, m));
370 return omref;
371 }
372
373 @Override
374 public Set<ModuleReference> findAll() {
375 if (allModules != null)
376 return allModules;
377 // seed with modules already found
378 Set<ModuleReference> result = new HashSet<>(nameToModule.values());
379 finderList.stream()
380 .flatMap(f -> f.findAll().stream())
381 .forEach(mref -> {
382 String name = mref.descriptor().name();
383 if (nameToModule.putIfAbsent(name, mref) == null) {
384 result.add(mref);
385 }
386 });
387 allModules = Collections.unmodifiableSet(result);
388 return allModules;
389 }
390 };
391 }
392
393 }