1 /* 2 * Copyright (c) 2007, 2018, 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.nio.file; 27 28 import java.nio.file.spi.FileSystemProvider; 29 import java.net.URI; 30 import java.io.IOException; 31 import java.security.AccessController; 32 import java.security.PrivilegedAction; 33 import java.lang.reflect.Constructor; 34 import java.util.Collections; 35 import java.util.Map; 36 import java.util.ServiceConfigurationError; 37 import java.util.ServiceLoader; 38 39 import jdk.internal.misc.VM; 40 import sun.nio.fs.DefaultFileSystemProvider; 41 42 /** 43 * Factory methods for file systems. This class defines the {@link #getDefault 44 * getDefault} method to get the default file system and factory methods to 45 * construct other types of file systems. 46 * 47 * <p> The first invocation of any of the methods defined by this class causes 48 * the default {@link FileSystemProvider provider} to be loaded. The default 49 * provider, identified by the URI scheme "file", creates the {@link FileSystem} 50 * that provides access to the file systems accessible to the Java virtual 51 * machine. If the process of loading or initializing the default provider fails 52 * then an unspecified error is thrown. 53 * 54 * <p> The first invocation of the {@link FileSystemProvider#installedProviders() 55 * installedProviders} method, by way of invoking any of the {@code 56 * newFileSystem} methods defined by this class, locates and loads all 57 * installed file system providers. Installed providers are loaded using the 58 * service-provider loading facility defined by the {@link ServiceLoader} class. 59 * Installed providers are loaded using the system class loader. If the 60 * system class loader cannot be found then the platform class loader is used. 61 * Providers are typically installed by placing them in a JAR file on the 62 * application class path, the JAR file contains a 63 * provider-configuration file named {@code java.nio.file.spi.FileSystemProvider} 64 * in the resource directory {@code META-INF/services}, and the file lists one or 65 * more fully-qualified names of concrete subclass of {@link FileSystemProvider} 66 * that have a zero argument constructor. 67 * The ordering that installed providers are located is implementation specific. 68 * If a provider is instantiated and its {@link FileSystemProvider#getScheme() 69 * getScheme} returns the same URI scheme of a provider that was previously 70 * instantiated then the most recently instantiated duplicate is discarded. URI 71 * schemes are compared without regard to case. During construction a provider 72 * may safely access files associated with the default provider but care needs 73 * to be taken to avoid circular loading of other installed providers. If 74 * circular loading of installed providers is detected then an unspecified error 75 * is thrown. 76 * 77 * <p> This class also defines factory methods that allow a {@link ClassLoader} 78 * to be specified when locating a provider. As with installed providers, the 79 * provider classes are identified by placing the provider configuration file 80 * in the resource directory {@code META-INF/services}. 81 * 82 * <p> If a thread initiates the loading of the installed file system providers 83 * and another thread invokes a method that also attempts to load the providers 84 * then the method will block until the loading completes. 85 * 86 * @since 1.7 87 */ 88 89 public final class FileSystems { 90 private FileSystems() { } 91 92 // lazy initialization of default file system 93 private static class DefaultFileSystemHolder { 94 static final FileSystem defaultFileSystem = defaultFileSystem(); 95 96 // returns default file system 97 private static FileSystem defaultFileSystem() { 98 // load default provider 99 FileSystemProvider provider = AccessController 100 .doPrivileged(new PrivilegedAction<>() { 101 public FileSystemProvider run() { 102 return getDefaultProvider(); 103 } 104 }); 105 106 // return file system 107 return provider.getFileSystem(URI.create("file:///")); 108 } 109 110 // returns default provider 111 private static FileSystemProvider getDefaultProvider() { 112 // start with the platform's default file system provider 113 FileSystemProvider provider = DefaultFileSystemProvider.instance(); 114 115 // if the property java.nio.file.spi.DefaultFileSystemProvider is 116 // set then its value is the name of the default provider (or a list) 117 String prop = "java.nio.file.spi.DefaultFileSystemProvider"; 118 String propValue = System.getProperty(prop); 119 if (propValue != null) { 120 for (String cn: propValue.split(",")) { 121 try { 122 Class<?> c = Class 123 .forName(cn, true, ClassLoader.getSystemClassLoader()); 124 Constructor<?> ctor = c 125 .getDeclaredConstructor(FileSystemProvider.class); 126 provider = (FileSystemProvider)ctor.newInstance(provider); 127 128 // must be "file" 129 if (!provider.getScheme().equals("file")) 130 throw new Error("Default provider must use scheme 'file'"); 131 132 } catch (Exception x) { 133 throw new Error(x); 134 } 135 } 136 } 137 return provider; 138 } 139 } 140 141 /** 142 * Returns the default {@code FileSystem}. The default file system creates 143 * objects that provide access to the file systems accessible to the Java 144 * virtual machine. The <em>working directory</em> of the file system is 145 * the current user directory, named by the system property {@code user.dir}. 146 * This allows for interoperability with the {@link java.io.File java.io.File} 147 * class. 148 * 149 * <p> The first invocation of any of the methods defined by this class 150 * locates the default {@link FileSystemProvider provider} object. Where the 151 * system property {@code java.nio.file.spi.DefaultFileSystemProvider} is 152 * not defined then the default provider is a system-default provider that 153 * is invoked to create the default file system. 154 * 155 * <p> If the system property {@code java.nio.file.spi.DefaultFileSystemProvider} 156 * is defined then it is taken to be a list of one or more fully-qualified 157 * names of concrete provider classes identified by the URI scheme 158 * {@code "file"}. Where the property is a list of more than one name then 159 * the names are separated by a comma. Each class is loaded, using the system 160 * class loader, and instantiated by invoking a one argument constructor 161 * whose formal parameter type is {@code FileSystemProvider}. The providers 162 * are loaded and instantiated in the order they are listed in the property. 163 * If this process fails or a provider's scheme is not equal to {@code "file"} 164 * then an unspecified error is thrown. URI schemes are normally compared 165 * without regard to case but for the default provider, the scheme is 166 * required to be {@code "file"}. The first provider class is instantiated 167 * by invoking it with a reference to the system-default provider. 168 * The second provider class is instantiated by invoking it with a reference 169 * to the first provider instance. The third provider class is instantiated 170 * by invoking it with a reference to the second instance, and so on. The 171 * last provider to be instantiated becomes the default provider; its {@code 172 * getFileSystem} method is invoked with the URI {@code "file:///"} to 173 * get a reference to the default file system. 174 * 175 * <p> Subsequent invocations of this method return the file system that was 176 * returned by the first invocation. 177 * 178 * @return the default file system 179 */ 180 public static FileSystem getDefault() { 181 if (VM.isModuleSystemInited()) { 182 return DefaultFileSystemHolder.defaultFileSystem; 183 } else { 184 // always use the platform's default file system during startup 185 return DefaultFileSystemProvider.theFileSystem(); 186 } 187 } 188 189 /** 190 * Returns a reference to an existing {@code FileSystem}. 191 * 192 * <p> This method iterates over the {@link FileSystemProvider#installedProviders() 193 * installed} providers to locate the provider that is identified by the URI 194 * {@link URI#getScheme scheme} of the given URI. URI schemes are compared 195 * without regard to case. The exact form of the URI is highly provider 196 * dependent. If found, the provider's {@link FileSystemProvider#getFileSystem 197 * getFileSystem} method is invoked to obtain a reference to the {@code 198 * FileSystem}. 199 * 200 * <p> Once a file system created by this provider is {@link FileSystem#close 201 * closed} it is provider-dependent if this method returns a reference to 202 * the closed file system or throws {@link FileSystemNotFoundException}. 203 * If the provider allows a new file system to be created with the same URI 204 * as a file system it previously created then this method throws the 205 * exception if invoked after the file system is closed (and before a new 206 * instance is created by the {@link #newFileSystem newFileSystem} method). 207 * 208 * <p> If a security manager is installed then a provider implementation 209 * may require to check a permission before returning a reference to an 210 * existing file system. In the case of the {@link FileSystems#getDefault 211 * default} file system, no permission check is required. 212 * 213 * @param uri the URI to locate the file system 214 * 215 * @return the reference to the file system 216 * 217 * @throws IllegalArgumentException 218 * if the pre-conditions for the {@code uri} parameter are not met 219 * @throws FileSystemNotFoundException 220 * if the file system, identified by the URI, does not exist 221 * @throws ProviderNotFoundException 222 * if a provider supporting the URI scheme is not installed 223 * @throws SecurityException 224 * if a security manager is installed and it denies an unspecified 225 * permission 226 */ 227 public static FileSystem getFileSystem(URI uri) { 228 String scheme = uri.getScheme(); 229 for (FileSystemProvider provider: FileSystemProvider.installedProviders()) { 230 if (scheme.equalsIgnoreCase(provider.getScheme())) { 231 return provider.getFileSystem(uri); 232 } 233 } 234 throw new ProviderNotFoundException("Provider \"" + scheme + "\" not found"); 235 } 236 237 /** 238 * Constructs a new file system that is identified by a {@link URI} 239 * 240 * <p> This method iterates over the {@link FileSystemProvider#installedProviders() 241 * installed} providers to locate the provider that is identified by the URI 242 * {@link URI#getScheme scheme} of the given URI. URI schemes are compared 243 * without regard to case. The exact form of the URI is highly provider 244 * dependent. If found, the provider's {@link FileSystemProvider#newFileSystem(URI,Map) 245 * newFileSystem(URI,Map)} method is invoked to construct the new file system. 246 * 247 * <p> Once a file system is {@link FileSystem#close closed} it is 248 * provider-dependent if the provider allows a new file system to be created 249 * with the same URI as a file system it previously created. 250 * 251 * <p> <b>Usage Example:</b> 252 * Suppose there is a provider identified by the scheme {@code "memory"} 253 * installed: 254 * <pre> 255 * Map<String,String> env = new HashMap<>(); 256 * env.put("capacity", "16G"); 257 * env.put("blockSize", "4k"); 258 * FileSystem fs = FileSystems.newFileSystem(URI.create("memory:///?name=logfs"), env); 259 * </pre> 260 * 261 * @param uri 262 * the URI identifying the file system 263 * @param env 264 * a map of provider specific properties to configure the file system; 265 * may be empty 266 * 267 * @return a new file system 268 * 269 * @throws IllegalArgumentException 270 * if the pre-conditions for the {@code uri} parameter are not met, 271 * or the {@code env} parameter does not contain properties required 272 * by the provider, or a property value is invalid 273 * @throws FileSystemAlreadyExistsException 274 * if the file system has already been created 275 * @throws ProviderNotFoundException 276 * if a provider supporting the URI scheme is not installed 277 * @throws IOException 278 * if an I/O error occurs creating the file system 279 * @throws SecurityException 280 * if a security manager is installed and it denies an unspecified 281 * permission required by the file system provider implementation 282 */ 283 public static FileSystem newFileSystem(URI uri, Map<String,?> env) 284 throws IOException 285 { 286 return newFileSystem(uri, env, null); 287 } 288 289 /** 290 * Constructs a new file system that is identified by a {@link URI} 291 * 292 * <p> This method first attempts to locate an installed provider in exactly 293 * the same manner as the {@link #newFileSystem(URI,Map) newFileSystem(URI,Map)} 294 * method. If none of the installed providers support the URI scheme then an 295 * attempt is made to locate the provider using the given class loader. If a 296 * provider supporting the URI scheme is located then its {@link 297 * FileSystemProvider#newFileSystem(URI,Map) newFileSystem(URI,Map)} is 298 * invoked to construct the new file system. 299 * 300 * @param uri 301 * the URI identifying the file system 302 * @param env 303 * a map of provider specific properties to configure the file system; 304 * may be empty 305 * @param loader 306 * the class loader to locate the provider or {@code null} to only 307 * attempt to locate an installed provider 308 * 309 * @return a new file system 310 * 311 * @throws IllegalArgumentException 312 * if the pre-conditions for the {@code uri} parameter are not met, 313 * or the {@code env} parameter does not contain properties required 314 * by the provider, or a property value is invalid 315 * @throws FileSystemAlreadyExistsException 316 * if the URI scheme identifies an installed provider and the file 317 * system has already been created 318 * @throws ProviderNotFoundException 319 * if a provider supporting the URI scheme is not found 320 * @throws ServiceConfigurationError 321 * when an error occurs while loading a service provider 322 * @throws IOException 323 * an I/O error occurs creating the file system 324 * @throws SecurityException 325 * if a security manager is installed and it denies an unspecified 326 * permission required by the file system provider implementation 327 */ 328 public static FileSystem newFileSystem(URI uri, Map<String,?> env, ClassLoader loader) 329 throws IOException 330 { 331 String scheme = uri.getScheme(); 332 333 // check installed providers 334 for (FileSystemProvider provider : FileSystemProvider.installedProviders()) { 335 if (scheme.equalsIgnoreCase(provider.getScheme())) { 336 try { 337 return provider.newFileSystem(uri, env); 338 } catch (UnsupportedOperationException uoe) { 339 } 340 } 341 } 342 343 // if not found, use service-provider loading facility 344 if (loader != null) { 345 ServiceLoader<FileSystemProvider> sl = ServiceLoader 346 .load(FileSystemProvider.class, loader); 347 for (FileSystemProvider provider : sl) { 348 if (scheme.equalsIgnoreCase(provider.getScheme())) { 349 try { 350 return provider.newFileSystem(uri, env); 351 } catch (UnsupportedOperationException uoe) { 352 } 353 } 354 } 355 } 356 357 throw new ProviderNotFoundException("Provider \"" + scheme + "\" not found"); 358 } 359 360 /** 361 * Constructs a new {@code FileSystem} to access the contents of a file as a 362 * file system. 363 * 364 * <p> This method makes use of specialized providers that create pseudo file 365 * systems where the contents of one or more files is treated as a file 366 * system. 367 * 368 * <p> This method iterates over the {@link FileSystemProvider#installedProviders() 369 * installed} providers. It invokes, in turn, each provider's {@link 370 * FileSystemProvider#newFileSystem(Path,Map) newFileSystem(Path,Map)} method 371 * with an empty map. If a provider returns a file system then the iteration 372 * terminates and the file system is returned. If none of the installed 373 * providers return a {@code FileSystem} then an attempt is made to locate 374 * the provider using the given class loader. If a provider returns a file 375 * system then the lookup terminates and the file system is returned. 376 * 377 * @param path 378 * the path to the file 379 * @param loader 380 * the class loader to locate the provider or {@code null} to only 381 * attempt to locate an installed provider 382 * 383 * @return a new file system 384 * 385 * @throws ProviderNotFoundException 386 * if a provider supporting this file type cannot be located 387 * @throws ServiceConfigurationError 388 * when an error occurs while loading a service provider 389 * @throws IOException 390 * if an I/O error occurs 391 * @throws SecurityException 392 * if a security manager is installed and it denies an unspecified 393 * permission 394 */ 395 public static FileSystem newFileSystem(Path path, 396 ClassLoader loader) 397 throws IOException 398 { 399 if (path == null) 400 throw new NullPointerException(); 401 Map<String,?> env = Collections.emptyMap(); 402 403 // check installed providers 404 for (FileSystemProvider provider: FileSystemProvider.installedProviders()) { 405 try { 406 return provider.newFileSystem(path, env); 407 } catch (UnsupportedOperationException uoe) { 408 } 409 } 410 411 // if not found, use service-provider loading facility 412 if (loader != null) { 413 ServiceLoader<FileSystemProvider> sl = ServiceLoader 414 .load(FileSystemProvider.class, loader); 415 for (FileSystemProvider provider: sl) { 416 try { 417 return provider.newFileSystem(path, env); 418 } catch (UnsupportedOperationException uoe) { 419 } 420 } 421 } 422 423 throw new ProviderNotFoundException("Provider not found"); 424 } 425 }