1 /*
   2  * Copyright (c) 2007, 2011, 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 
  31 /**
  32  * This class consists exclusively of static methods that return a {@link Path}
  33  * by converting a path string or {@link URI}.
  34  *
  35  * @since 1.7
  36  */
  37 
  38 public final class Paths {
  39     private Paths() { }
  40 
  41     /**
  42      * Converts a path string, or a sequence of strings that when joined form
  43      * a path string, to a {@code Path}. If {@code more} does not specify any
  44      * elements then the value of the {@code first} parameter is the path string
  45      * to convert. If {@code more} specifies one or more elements then each
  46      * non-empty string, including {@code first}, is considered to be a sequence
  47      * of name elements (see {@link Path}) and is joined to form a path string.
  48      * The details as to how the Strings are joined is provider specific but
  49      * typically they will be joined using the {@link FileSystem#getSeparator
  50      * name-separator} as the separator. For example, if the name separator is
  51      * "{@code /}" and {@code getPath("/foo","bar","gus")} is invoked, then the
  52      * path string {@code "/foo/bar/gus"} is converted to a {@code Path}.
  53      * A {@code Path} representing an empty path is returned if {@code first}
  54      * is the empty string and {@code more} does not contain any non-empty
  55      * strings.
  56      *
  57      * <p> The {@code Path} is obtained by invoking the {@link FileSystem#getPath
  58      * getPath} method of the {@link FileSystems#getDefault default} {@link
  59      * FileSystem}.
  60      *
  61      * <p> Note that while this method is very convenient, using it will imply
  62      * an assumed reference to the default {@code FileSystem} and limit the
  63      * utility of the calling code. Hence it should not be used in library code
  64      * intended for flexible reuse. A more flexible alternative is to use an
  65      * existing {@code Path} instance as an anchor, such as:
  66      * <pre>
  67      *     Path dir = ...
  68      *     Path path = dir.resolve("file");
  69      * </pre>
  70      *
  71      * @param   first
  72      *          the path string or initial part of the path string
  73      * @param   more
  74      *          additional strings to be joined to form the path string
  75      *
  76      * @return  the resulting {@code Path}
  77      *
  78      * @throws  InvalidPathException
  79      *          if the path string cannot be converted to a {@code Path}
  80      *
  81      * @see FileSystem#getPath
  82      */
  83     public static Path get(String first, String... more) {
  84         return FileSystems.getDefault().getPath(first, more);
  85     }
  86 
  87     /**
  88      * Converts the given URI to a {@link Path} object.
  89      *
  90      * <p> This method iterates over the {@link FileSystemProvider#installedProviders()
  91      * installed} providers to locate the provider that is identified by the
  92      * URI {@link URI#getScheme scheme} of the given URI. URI schemes are
  93      * compared without regard to case. If the provider is found then its {@link
  94      * FileSystemProvider#getPath getPath} method is invoked to convert the
  95      * URI.
  96      *
  97      * <p> In the case of the default provider, identified by the URI scheme
  98      * "file", the given URI has a non-empty path component, and undefined query
  99      * and fragment components. Whether the authority component may be present
 100      * is platform specific. The returned {@code Path} is associated with the
 101      * {@link FileSystems#getDefault default} file system.
 102      *
 103      * <p> The default provider provides a similar <em>round-trip</em> guarantee
 104      * to the {@link java.io.File} class. For a given {@code Path} <i>p</i> it
 105      * is guaranteed that
 106      * <blockquote>{@code
 107      * Paths.get(}<i>p</i>{@code .}{@link Path#toUri() toUri}{@code ()).equals(}
 108      * <i>p</i>{@code .}{@link Path#toAbsolutePath() toAbsolutePath}{@code ())}
 109      * </blockquote>
 110      * so long as the original {@code Path}, the {@code URI}, and the new {@code
 111      * Path} are all created in (possibly different invocations of) the same
 112      * Java virtual machine. Whether other providers make any guarantees is
 113      * provider specific and therefore unspecified.
 114      *
 115      * @param   uri
 116      *          the URI to convert
 117      *
 118      * @return  the resulting {@code Path}
 119      *
 120      * @throws  IllegalArgumentException
 121      *          if preconditions on the {@code uri} parameter do not hold. The
 122      *          format of the URI is provider specific.
 123      * @throws  FileSystemNotFoundException
 124      *          The file system, identified by the URI, does not exist and
 125      *          cannot be created automatically, or the provider identified by
 126      *          the URI's scheme component is not installed
 127      * @throws  SecurityException
 128      *          if a security manager is installed and it denies an unspecified
 129      *          permission to access the file system
 130      */
 131     public static Path get(URI uri) {
 132         String scheme =  uri.getScheme();
 133         if (scheme == null)
 134             throw new IllegalArgumentException("Missing scheme");
 135 
 136         // check for default provider to avoid loading of installed providers
 137         if (scheme.equalsIgnoreCase("file"))
 138             return FileSystems.getDefault().provider().getPath(uri);
 139 
 140         // try to find provider
 141         for (FileSystemProvider provider: FileSystemProvider.installedProviders()) {
 142             if (provider.getScheme().equalsIgnoreCase(scheme)) {
 143                 return provider.getPath(uri);
 144             }
 145         }
 146 
 147         throw new FileSystemNotFoundException("Provider \"" + scheme + "\" not installed");
 148     }
 149 }