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 26package java.lang.module; 27 28import java.nio.file.Path; 29import java.security.AccessController; 30import java.security.Permission; 31import java.security.PrivilegedAction; 32import java.util.Collections; 33import java.util.HashMap; 34import java.util.HashSet; 35import java.util.List; 36import java.util.Map; 37import java.util.Objects; 38import java.util.Optional; 39import java.util.Set; 40 41import jdk.internal.module.ModulePath; 42import jdk.internal.module.SystemModuleFinders; 43 44/** 45 * A finder of modules. A {@code ModuleFinder} is used to find modules during 46 * <a href="package-summary.html#resolution">resolution</a> or 47 * <a href="Configuration.html#service-binding">service binding</a>. 48 * 49 * <p> A {@code ModuleFinder} can only find one module with a given name. A 50 * {@code ModuleFinder} that finds modules in a sequence of directories, for 51 * example, will locate the first occurrence of a module of a given name and 52 * will ignore other modules of that name that appear in directories later in 53 * the sequence. </p> 54 * 55 * <p> Example usage: </p> 56 * 57 * <pre>{@code 58 * Path dir1, dir2, dir3; 59 * 60 * ModuleFinder finder = ModuleFinder.of(dir1, dir2, dir3); 61 * 62 * Optional<ModuleReference> omref = finder.find("jdk.foo"); 63 * omref.ifPresent(mref -> ... ); 64 * 65 * }</pre> 66 * 67 * <p> The {@link #find(String) find} and {@link #findAll() findAll} methods 68 * defined here can fail for several reasons. These include I/O errors, errors 69 * detected parsing a module descriptor ({@code module-info.class}), or in the 70 * case of {@code ModuleFinder} returned by {@link #of ModuleFinder.of}, that 71 * two or more modules with the same name are found in a directory. 72 * When an error is detected then these methods throw {@link FindException 73 * FindException} with an appropriate {@link Throwable#getCause cause}. 74 * The behavior of a {@code ModuleFinder} after a {@code FindException} is 75 * thrown is undefined. For example, invoking {@code find} after an exception 76 * is thrown may or may not scan the same modules that lead to the exception. 77 * It is recommended that a module finder be discarded after an exception is 78 * thrown. </p> 79 * 80 * <p> A {@code ModuleFinder} is not required to be thread safe. </p> 81 * 82 * @since 9 83 * @spec JPMS 84 */ 85 86public interface ModuleFinder { 87 88 /** 89 * Finds a reference to a module of a given name. 90 * 91 * <p> A {@code ModuleFinder} provides a consistent view of the 92 * modules that it locates. If {@code find} is invoked several times to 93 * locate the same module (by name) then it will return the same result 94 * each time. If a module is located then it is guaranteed to be a member 95 * of the set of modules returned by the {@link #findAll() findAll} 96 * method. </p> 97 * 98 * @param name 99 * The name of the module to find 100 * 101 * @return A reference to a module with the given name or an empty 102 * {@code Optional} if not found 103 * 104 * @throws FindException 105 * If an error occurs finding the module 106 * 107 * @throws SecurityException 108 * If denied by the security manager 109 */ 110 Optional<ModuleReference> find(String name); 111 112 /** 113 * Returns the set of all module references that this finder can locate. 114 * 115 * <p> A {@code ModuleFinder} provides a consistent view of the modules 116 * that it locates. If {@link #findAll() findAll} is invoked several times 117 * then it will return the same (equals) result each time. For each {@code 118 * ModuleReference} element in the returned set then it is guaranteed that 119 * {@link #find find} will locate the {@code ModuleReference} if invoked 120 * to find that module. </p> 121 * 122 * @apiNote This is important to have for methods such as {@link 123 * Configuration#resolveAndBind resolveAndBind} that need to scan the 124 * module path to find modules that provide a specific service. 125 * 126 * @return The set of all module references that this finder locates 127 * 128 * @throws FindException 129 * If an error occurs finding all modules 130 * 131 * @throws SecurityException 132 * If denied by the security manager 133 */ 134 Set<ModuleReference> findAll(); 135 136 /** 137 * Returns a module finder that locates the <em>system modules</em>. The 138 * system modules are the modules in the Java run-time image. 139 * The module finder will always find {@code java.base}. 140 * 141 * <p> If there is a security manager set then its {@link 142 * SecurityManager#checkPermission(Permission) checkPermission} method is 143 * invoked to check that the caller has been granted 144 * {@link RuntimePermission RuntimePermission("accessSystemModules")} 145 * to access the system modules. </p> 146 * 147 * @return A {@code ModuleFinder} that locates the system modules 148 * 149 * @throws SecurityException 150 * If denied by the security manager 151 */ 152 static ModuleFinder ofSystem() { 153 SecurityManager sm = System.getSecurityManager(); 154 if (sm != null) { 155 sm.checkPermission(new RuntimePermission("accessSystemModules")); 156 PrivilegedAction<ModuleFinder> pa = SystemModuleFinders::ofSystem; 157 return AccessController.doPrivileged(pa); 158 } else { 159 return SystemModuleFinders.ofSystem(); 160 } 161 } 162 163 /** 164 * Returns a module finder that locates modules on the file system by 165 * searching a sequence of directories and/or packaged modules. 166 * 167 * Each element in the given array is one of: 168 * <ol> 169 * <li><p> A path to a directory of modules.</p></li> 170 * <li><p> A path to the <em>top-level</em> directory of an 171 * <em>exploded module</em>. </p></li> 172 * <li><p> A path to a <em>packaged module</em>. </p></li> 173 * </ol> 174 * 175 * The module finder locates modules by searching each directory, exploded 176 * module, or packaged module in array index order. It finds the first 177 * occurrence of a module with a given name and ignores other modules of 178 * that name that appear later in the sequence. 179 * 180 * <p> If an element is a path to a directory of modules then each entry in 181 * the directory is a packaged module or the top-level directory of an 182 * exploded module. It is an error if a directory contains more than one 183 * module with the same name. If an element is a path to a directory, and 184 * that directory contains a file named {@code module-info.class}, then the 185 * directory is treated as an exploded module rather than a directory of 186 * modules. </p> 187 * 188 * <p id="automatic-modules"> The module finder returned by this method 189 * supports modules packaged as JAR files. A JAR file with a {@code 190 * module-info.class} in its top-level directory, or in a versioned entry 191 * in a {@linkplain java.util.jar.JarFile#isMultiRelease() multi-release} 192 * JAR file, is a modular JAR file and thus defines an <em>explicit</em> 193 * module. A JAR file that does not have a {@code module-info.class} in its 194 * top-level directory defines an <em>automatic module</em>, as follows: 195 * </p> 196 * 197 * <ul> 198 * 199 * <li><p> If the JAR file has the attribute "{@code Automatic-Module-Name}" 200 * in its main manifest then its value is the {@linkplain 201 * ModuleDescriptor#name() module name}. The module name is otherwise 202 * derived from the name of the JAR file. </p></li> 203 * 204 * <li><p> The {@link ModuleDescriptor#version() version}, and the 205 * module name when the attribute "{@code Automatic-Module-Name}" is not 206 * present, are derived from the file name of the JAR file as follows: </p> 207 * 208 * <ul> 209 * 210 * <li><p> The "{@code .jar}" suffix is removed. </p></li> 211 * 212 * <li><p> If the name matches the regular expression {@code 213 * "-(\\d+(\\.|$))"} then the module name will be derived from the 214 * subsequence preceding the hyphen of the first occurrence. The 215 * subsequence after the hyphen is parsed as a {@link 216 * ModuleDescriptor.Version Version} and ignored if it cannot be 217 * parsed as a {@code Version}. </p></li> 218 * 219 * <li><p> All non-alphanumeric characters ({@code [^A-Za-z0-9]}) 220 * in the module name are replaced with a dot ({@code "."}), all 221 * repeating dots are replaced with one dot, and all leading and 222 * trailing dots are removed. </p></li> 223 * 224 * <li><p> As an example, a JAR file named "{@code foo-bar.jar}" will 225 * derive a module name "{@code foo.bar}" and no version. A JAR file 226 * named "{@code foo-bar-1.2.3-SNAPSHOT.jar}" will derive a module 227 * name "{@code foo.bar}" and "{@code 1.2.3-SNAPSHOT}" as the version. 228 * </p></li> 229 * 230 * </ul></li> 231 * 232 * <li><p> The set of packages in the module is derived from the 233 * non-directory entries in the JAR file that have names ending in 234 * "{@code .class}". A candidate package name is derived from the name 235 * using the characters up to, but not including, the last forward slash. 236 * All remaining forward slashes are replaced with dot ({@code "."}). If 237 * the resulting string is a legal package name then it is assumed to be 238 * a package name. For example, if the JAR file contains the entry 239 * "{@code p/q/Foo.class}" then the package name derived is 240 * "{@code p.q}".</p></li> 241 * 242 * <li><p> The contents of entries starting with {@code 243 * META-INF/services/} are assumed to be service configuration files 244 * (see {@link java.util.ServiceLoader}). If the name of a file 245 * (that follows {@code META-INF/services/}) is a legal class name 246 * then it is assumed to be the fully-qualified class name of a service 247 * type. The entries in the file are assumed to be the fully-qualified 248 * class names of provider classes. </p></li> 249 * 250 * <li><p> If the JAR file has a {@code Main-Class} attribute in its 251 * main manifest, its value is a legal class name, and its package is 252 * in the set of packages derived for the module, then the value is the 253 * module {@linkplain ModuleDescriptor#mainClass() main class}. </p></li> 254 * 255 * </ul> 256 * 257 * <p> If a {@code ModuleDescriptor} cannot be created (by means of the 258 * {@link ModuleDescriptor.Builder ModuleDescriptor.Builder} API) for an 259 * automatic module then {@code FindException} is thrown. This can arise 260 * when the value of the "{@code Automatic-Module-Name}" attribute is not a 261 * legal module name, a legal module name cannot be derived from the file 262 * name of the JAR file, where the JAR file contains a {@code .class} in 263 * the top-level directory of the JAR file, where an entry in a service 264 * configuration file is not a legal class name or its package name is not 265 * in the set of packages derived for the module. </p> 266 * 267 * <p> In addition to JAR files, an implementation may also support modules 268 * that are packaged in other implementation specific module formats. If 269 * an element in the array specified to this method is a path to a directory 270 * of modules then entries in the directory that not recognized as modules 271 * are ignored. If an element in the array is a path to a packaged module 272 * that is not recognized then a {@code FindException} is thrown when the 273 * file is encountered. Paths to files that do not exist are always ignored. 274 * </p> 275 * 276 * <p> As with automatic modules, the contents of a packaged or exploded 277 * module may need to be <em>scanned</em> in order to determine the packages 278 * in the module. Whether {@linkplain java.nio.file.Files#isHidden(Path) 279 * hidden files} are ignored or not is implementation specific and therefore 280 * not specified. If a {@code .class} file (other than {@code 281 * module-info.class}) is found in the top-level directory then it is 282 * assumed to be a class in the unnamed package and so {@code FindException} 283 * is thrown. </p> 284 * 285 * <p> Finders created by this method are lazy and do not eagerly check 286 * that the given file paths are directories or packaged modules. 287 * Consequently, the {@code find} or {@code findAll} methods will only 288 * fail if invoking these methods results in searching a directory or 289 * packaged module and an error is encountered. </p> 290 * 291 * @param entries 292 * A possibly-empty array of paths to directories of modules 293 * or paths to packaged or exploded modules 294 * 295 * @return A {@code ModuleFinder} that locates modules on the file system 296 */ 297 static ModuleFinder of(Path... entries) { 298 // special case zero entries 299 if (entries.length == 0) { 300 return new ModuleFinder() { 301 @Override 302 public Optional<ModuleReference> find(String name) { 303 Objects.requireNonNull(name); 304 return Optional.empty(); 305 } 306 307 @Override 308 public Set<ModuleReference> findAll() { 309 return Collections.emptySet(); 310 } 311 }; 312 } 313 314 return ModulePath.of(entries); 315 } 316 317 /** 318 * Returns a module finder that is composed from a sequence of zero or more 319 * module finders. The {@link #find(String) find} method of the resulting 320 * module finder will locate a module by invoking the {@code find} method 321 * of each module finder, in array index order, until either the module is 322 * found or all module finders have been searched. The {@link #findAll() 323 * findAll} method of the resulting module finder will return a set of 324 * modules that includes all modules located by the first module finder. 325 * The set of modules will include all modules located by the second or 326 * subsequent module finder that are not located by previous module finders 327 * in the sequence. 328 * 329 * <p> When locating modules then any exceptions or errors thrown by the 330 * {@code find} or {@code findAll} methods of the underlying module finders 331 * will be propagated to the caller of the resulting module finder's 332 * {@code find} or {@code findAll} methods. </p> 333 * 334 * @param finders 335 * The array of module finders 336 * 337 * @return A {@code ModuleFinder} that composes a sequence of module finders 338 */ 339 static ModuleFinder compose(ModuleFinder... finders) { 340 // copy the list and check for nulls 341 final List<ModuleFinder> finderList = List.of(finders); 342 343 return new ModuleFinder() { 344 private final Map<String, ModuleReference> nameToModule = new HashMap<>(); 345 private Set<ModuleReference> allModules; 346 347 @Override 348 public Optional<ModuleReference> find(String name) { 349 // cached? 350 ModuleReference mref = nameToModule.get(name); 351 if (mref != null) 352 return Optional.of(mref); 353 Optional<ModuleReference> omref = finderList.stream() 354 .map(f -> f.find(name)) 355 .flatMap(Optional::stream) 356 .findFirst(); 357 omref.ifPresent(m -> nameToModule.put(name, m)); 358 return omref; 359 } 360 361 @Override 362 public Set<ModuleReference> findAll() { 363 if (allModules != null) 364 return allModules; 365 // seed with modules already found 366 Set<ModuleReference> result = new HashSet<>(nameToModule.values()); 367 finderList.stream() 368 .flatMap(f -> f.findAll().stream()) 369 .forEach(mref -> { 370 String name = mref.descriptor().name(); 371 if (nameToModule.putIfAbsent(name, mref) == null) { 372 result.add(mref); 373 } 374 }); 375 allModules = Collections.unmodifiableSet(result); 376 return allModules; 377 } 378 }; 379 } 380 381} 382