1 /* 2 * Copyright (c) 2014, 2016, 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="Configuration.html#resolution">resolution</a> or 52 * <a href="Configuration.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 */ 89 90 public interface ModuleFinder { 91 92 /** 93 * Finds a reference to a module of a given name. 94 * 95 * <p> A {@code ModuleFinder} provides a consistent view of the 96 * modules that it locates. If {@code find} is invoked several times to 97 * locate the same module (by name) then it will return the same result 98 * each time. If a module is located then it is guaranteed to be a member 99 * of the set of modules returned by the {@link #findAll() findAll} 100 * method. </p> 101 * 102 * @param name 103 * The name of the module to find 104 * 105 * @return A reference to a module with the given name or an empty 106 * {@code Optional} if not found 107 * 108 * @throws FindException 109 * If an error occurs finding the module 110 * 111 * @throws SecurityException 112 * If denied by the security manager 113 */ 114 Optional<ModuleReference> find(String name); 115 116 /** 117 * Returns the set of all module references that this finder can locate. 118 * 119 * <p> A {@code ModuleFinder} provides a consistent view of the modules 120 * that it locates. If {@link #findAll() findAll} is invoked several times 121 * then it will return the same (equals) result each time. For each {@code 122 * ModuleReference} element in the returned set then it is guaranteed that 123 * {@link #find find} will locate the {@code ModuleReference} if invoked 124 * to find that module. </p> 125 * 126 * @apiNote This is important to have for methods such as {@link 127 * Configuration#resolveRequiresAndUses resolveRequiresAndUses} that need 128 * to scan the module path to find modules that provide a specific service. 129 * 130 * @return The set of all module references that this finder locates 131 * 132 * @throws FindException 133 * If an error occurs finding all modules 134 * 135 * @throws SecurityException 136 * If denied by the security manager 137 */ 138 Set<ModuleReference> findAll(); 139 140 /** 141 * Returns a module finder that locates the <em>system modules</em>. The 142 * system modules are the modules in the Java run-time image. 143 * The module finder will always find {@code java.base}. 144 * 145 * <p> If there is a security manager set then its {@link 146 * SecurityManager#checkPermission(Permission) checkPermission} method is 147 * invoked to check that the caller has been granted {@link FilePermission} 148 * to recursively read the directory that is the value of the system 149 * property {@code java.home}. </p> 150 * 151 * @return A {@code ModuleFinder} that locates the system modules 152 * 153 * @throws SecurityException 154 * If denied by the security manager 155 */ 156 static ModuleFinder ofSystem() { 157 String home; 158 159 SecurityManager sm = System.getSecurityManager(); 160 if (sm != null) { 161 PrivilegedAction<String> pa = new GetPropertyAction("java.home"); 162 home = AccessController.doPrivileged(pa); 163 Permission p = new FilePermission(home + File.separator + "-", "read"); 164 sm.checkPermission(p); 165 } else { 166 home = System.getProperty("java.home"); 167 } 168 169 Path modules = Paths.get(home, "lib", "modules"); 170 if (Files.isRegularFile(modules)) { 171 return SystemModuleFinder.getInstance(); 172 } else { 173 Path mlib = Paths.get(home, "modules"); 174 if (Files.isDirectory(mlib)) { 175 return of(mlib); 176 } else { 177 throw new InternalError("Unable to detect the run-time image"); 178 } 179 } 180 } 181 182 /** 183 * Returns a module finder that locates modules on the file system by 184 * searching a sequence of directories and/or packaged modules. 185 * 186 * Each element in the given array is one of: 187 * <ol> 188 * <li><p> A path to a directory of modules.</p></li> 189 * <li><p> A path to the <em>top-level</em> directory of an 190 * <em>exploded module</em>. </p></li> 191 * <li><p> A path to a <em>packaged module</em>. </p></li> 192 * </ol> 193 * 194 * The module finder locates modules by searching each directory, exploded 195 * module, or packaged module in array index order. It finds the first 196 * occurrence of a module with a given name and ignores other modules of 197 * that name that appear later in the sequence. 198 * 199 * <p> If an element is a path to a directory of modules then each entry in 200 * the directory is a packaged module or the top-level directory of an 201 * exploded module. The module finder's {@link #find(String) find} or 202 * {@link #findAll() findAll} methods throw {@link FindException} if a 203 * directory containing more than one module with the same name is 204 * encountered. </p> 205 * 206 * <p> If an element in the array is a path to a directory, and that 207 * directory contains a file named {@code module-info.class}, then the 208 * directory is treated as an exploded module rather than a directory of 209 * modules. </p> 210 * 211 * <p> The module finder returned by this method supports modules that are 212 * packaged as JAR files. A JAR file with a {@code module-info.class} in 213 * the top-level directory of the JAR file (or overridden by a versioned 214 * entry in a {@link java.util.jar.JarFile#isMultiRelease() multi-release} 215 * JAR file) is a modular JAR and is an <em>explicit module</em>. 216 * A JAR file that does not have a {@code module-info.class} in the 217 * top-level directory is an {@link ModuleDescriptor#isAutomatic automatic} 218 * module. The {@link ModuleDescriptor} for an automatic module is created as 219 * follows: 220 * 221 * <ul> 222 * 223 * <li><p> The module {@link ModuleDescriptor#name() name}, and {@link 224 * ModuleDescriptor#version() version} if applicable, is derived from 225 * the file name of the JAR file as follows: </p> 226 * 227 * <ul> 228 * 229 * <li><p> The {@code .jar} suffix is removed. </p></li> 230 * 231 * <li><p> If the name matches the regular expression {@code 232 * "-(\\d+(\\.|$))"} then the module name will be derived from the 233 * subsequence preceding the hyphen of the first occurrence. The 234 * subsequence after the hyphen is parsed as a {@link 235 * ModuleDescriptor.Version} and ignored if it cannot be parsed as 236 * a {@code Version}. </p></li> 237 * 238 * <li><p> For the module name, then any trailing digits and dots 239 * are removed, all non-alphanumeric characters ({@code [^A-Za-z0-9]}) 240 * are replaced with a dot ({@code "."}), all repeating dots are 241 * replaced with one dot, and all leading and trailing dots are 242 * removed. </p></li> 243 * 244 * <li><p> As an example, a JAR file named {@code foo-bar.jar} will 245 * derive a module name {@code foo.bar} and no version. A JAR file 246 * named {@code foo-1.2.3-SNAPSHOT.jar} will derive a module name 247 * {@code foo} and {@code 1.2.3-SNAPSHOT} as the version. </p></li> 248 * 249 * </ul></li> 250 * 251 * <li><p> It {@link ModuleDescriptor#requires() requires} {@code 252 * java.base}. </p></li> 253 * 254 * <li><p> The set of packages in the module is derived from the names 255 * of non-directory entries in the JAR file. A candidate package name 256 * is derived from an entry using the characters up to, but not 257 * including, the last forward slash. All remaining forward slashes are 258 * replaced with dot ({@code "."}). If the resulting string is a valid 259 * Java identifier then it is assumed to be a package name. For example, 260 * if the JAR file contains an entry "{@code p/q/Foo.class}" then the 261 * package name derived is "{@code p.q}". All packages are {@link 262 * ModuleDescriptor#exports() exported}. </p></li> 263 * 264 * <li><p> The contents of entries starting with {@code 265 * META-INF/services/} are assumed to be service configuration files 266 * (see {@link java.util.ServiceLoader}). If the name of a file 267 * (that follows {@code META-INF/services/}) is a legal Java identifier 268 * then it is assumed to be the fully-qualified binary name of a 269 * service type. The entries in the file are assumed to be the 270 * fully-qualified binary names of provider classes. </p></li> 271 * 272 * <li><p> If the JAR file has a {@code Main-Class} attribute in its 273 * main manifest then its value is the {@link 274 * ModuleDescriptor#mainClass() main class}. </p></li> 275 * 276 * </ul> 277 * 278 * <p> If a {@code ModuleDescriptor} cannot be created (by means of the 279 * {@link ModuleDescriptor.Builder ModuleDescriptor.Builder} API) for an 280 * automatic module then {@code FindException} is thrown. This can arise, 281 * for example, when a legal Java identifier name cannot be derived from 282 * the file name of the JAR file or where the JAR file contains a {@code 283 * .class} in the top-level directory of the JAR file. </p> 284 * 285 * <p> In addition to JAR files, an implementation may also support modules 286 * that are packaged in other implementation specific module formats. When 287 * a file is encountered that is not recognized as a packaged module then 288 * {@code FindException} is thrown. An implementation may choose to ignore 289 * some files, {@link java.nio.file.Files#isHidden hidden} files for 290 * example. Paths to files that do not exist are always ignored. </p> 291 * 292 * <p> As with automatic modules, the contents of a packaged or exploded 293 * module may need to be <em>scanned</em> in order to determine the packages 294 * in the module. If a {@code .class} file (other than {@code 295 * module-info.class}) is found in the top-level directory then it is 296 * assumed to be a class in the unnamed package and so {@code FindException} 297 * is thrown. </p> 298 * 299 * <p> Finders created by this method are lazy and do not eagerly check 300 * that the given file paths are directories or packaged modules. 301 * Consequently, the {@code find} or {@code findAll} methods will only 302 * fail if invoking these methods results in searching a directory or 303 * packaged module and an error is encountered. </p> 304 * 305 * @param entries 306 * A possibly-empty array of paths to directories of modules 307 * or paths to packaged or exploded modules 308 * 309 * @return A {@code ModuleFinder} that locates modules on the file system 310 */ 311 static ModuleFinder of(Path... entries) { 312 // special case zero entries 313 if (entries.length == 0) { 314 return new ModuleFinder() { 315 @Override 316 public Optional<ModuleReference> find(String name) { 317 Objects.requireNonNull(name); 318 return Optional.empty(); 319 } 320 321 @Override 322 public Set<ModuleReference> findAll() { 323 return Collections.emptySet(); 324 } 325 }; 326 } 327 328 return new ModulePath(entries); 329 } 330 331 /** 332 * Returns a module finder that is composed from a sequence of zero or more 333 * module finders. The {@link #find(String) find} method of the resulting 334 * module finder will locate a module by invoking the {@code find} method 335 * of each module finder, in array index order, until either the module is 336 * found or all module finders have been searched. The {@link #findAll() 337 * findAll} method of the resulting module finder will return a set of 338 * modules that includes all modules located by the first module finder. 339 * The set of modules will include all modules located by the second or 340 * subsequent module finder that are not located by previous module finders 341 * in the sequence. 342 * 343 * <p> When locating modules then any exceptions or errors thrown by the 344 * {@code find} or {@code findAll} methods of the underlying module finders 345 * will be propagated to the caller of the resulting module finder's 346 * {@code find} or {@code findAll} methods. </p> 347 * 348 * @param finders 349 * The array of module finders 350 * 351 * @return A {@code ModuleFinder} that composes a sequence of module finders 352 */ 353 static ModuleFinder compose(ModuleFinder... finders) { 354 // copy the list and check for nulls 355 final List<ModuleFinder> finderList = List.of(finders); 356 357 return new ModuleFinder() { 358 private final Map<String, ModuleReference> nameToModule = new HashMap<>(); 359 private Set<ModuleReference> allModules; 360 361 @Override 362 public Optional<ModuleReference> find(String name) { 363 // cached? 364 ModuleReference mref = nameToModule.get(name); 365 if (mref != null) 366 return Optional.of(mref); 367 Optional<ModuleReference> omref = finderList.stream() 368 .map(f -> f.find(name)) 369 .flatMap(Optional::stream) 370 .findFirst(); 371 omref.ifPresent(m -> nameToModule.put(name, m)); 372 return omref; 373 } 374 375 @Override 376 public Set<ModuleReference> findAll() { 377 if (allModules != null) 378 return allModules; 379 // seed with modules already found 380 Set<ModuleReference> result = new HashSet<>(nameToModule.values()); 381 finderList.stream() 382 .flatMap(f -> f.findAll().stream()) 383 .forEach(mref -> { 384 String name = mref.descriptor().name(); 385 if (nameToModule.putIfAbsent(name, mref) == null) { 386 result.add(mref); 387 } 388 }); 389 allModules = Collections.unmodifiableSet(result); 390 return allModules; 391 } 392 }; 393 } 394 395 }