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| 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.attribute.BasicFileAttributes; | ||
| 29 | import java.io.IOException; | ||
| 30 | |||
| 31 | /** | ||
| 32 | * A visitor of files. An implementation of this interface is provided to the | ||
| 33 | * {@link Files#walkFileTree Files.walkFileTree} methods to visit each file in | ||
| 34 | * a file tree. | ||
| 35 | * | ||
| 36 | * <p> <b>Usage Examples:</b> | ||
| 37 | * Suppose we want to delete a file tree. In that case, each directory should | ||
| 38 | * be deleted after the entries in the directory are deleted. | ||
| 39 | * <pre> | ||
| 40 | * Path start = ... | ||
| 41 | * Files.walkFileTree(start, new SimpleFileVisitor<Path>() { | ||
| 42 | * @Override | ||
| 43 | * public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) | ||
| 44 | * throws IOException | ||
| 45 | * { | ||
| 46 | * Files.delete(file); | ||
| 47 | * return FileVisitResult.CONTINUE; | ||
| 48 | * } | ||
| 49 | * @Override | ||
| 50 | * public FileVisitResult postVisitDirectory(Path dir, IOException e) | ||
| 51 | * throws IOException | ||
| 52 | * { | ||
| 53 | * if (e == null) { | ||
| 54 | * Files.delete(dir); | ||
| 55 | * return FileVisitResult.CONTINUE; | ||
| 56 | * } else { | ||
| 57 | * // directory iteration failed | ||
| 58 | * throw e; | ||
| 59 | * } | ||
| 60 | * } | ||
| 61 | * }); | ||
| 62 | * </pre> | ||
| 63 | * <p> Furthermore, suppose we want to copy a file tree to a target location. | ||
| 64 | * In that case, symbolic links should be followed and the target directory | ||
| 65 | * should be created before the entries in the directory are copied. | ||
| 66 | * <pre> | ||
| 67 | * final Path source = ... | ||
| 68 | * final Path target = ... | ||
| 69 | * | ||
| 70 | * Files.walkFileTree(source, EnumSet.of(FileVisitOption.FOLLOW_LINKS), Integer.MAX_VALUE, | ||
| 71 | * new SimpleFileVisitor<Path>() { | ||
| 72 | * @Override | ||
| 73 | * public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) | ||
| 74 | * throws IOException | ||
| 75 | * { | ||
| 76 | * Path targetdir = target.resolve(source.relativize(dir)); | ||
| 77 | * try { | ||
| 78 | * Files.copy(dir, targetdir); | ||
| 79 | * } catch (FileAlreadyExistsException e) { | ||
| 80 | * if (!Files.isDirectory(targetdir)) | ||
| 81 | * throw e; | ||
| 82 | * } | ||
| 83 | * return CONTINUE; | ||
| 84 | * } | ||
| 85 | * @Override | ||
| 86 | * public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) | ||
| 87 | * throws IOException | ||
| 88 | * { | ||
| 89 | * Files.copy(file, target.resolve(source.relativize(file))); | ||
| 90 | * return CONTINUE; | ||
| 91 | * } | ||
| 92 | * }); | ||
| 93 | * </pre> | ||
| 94 | * | ||
| 95 | * @since 1.7 | ||
| 96 | */ | ||
| 97 | |||
| 98 | public interface FileVisitor<T> { | ||
| 99 | |||
| 100 | /** | ||
| 101 | * Invoked for a directory before entries in the directory are visited. | ||
| 102 | * | ||
| 103 | * <p> If this method returns {@link FileVisitResult#CONTINUE CONTINUE}, | ||
| 104 | * then entries in the directory are visited. If this method returns {@link | ||
| 105 | * FileVisitResult#SKIP_SUBTREE SKIP_SUBTREE} or {@link | ||
| 106 | * FileVisitResult#SKIP_SIBLINGS SKIP_SIBLINGS} then entries in the | ||
| 107 | * directory (and any descendants) will not be visited. | ||
| 108 | * | ||
| 109 | * @param dir | ||
| 110 | * a reference to the directory | ||
| 111 | * @param attrs | ||
| 112 | * the directory's basic attributes | ||
| 113 | * | ||
| 114 | * @return the visit result | ||
| 115 | * | ||
| 116 | * @throws IOException | ||
| 117 | * if an I/O error occurs | ||
| 118 | */ | ||
| 119 | FileVisitResult preVisitDirectory(T dir, BasicFileAttributes attrs) | ||
| 120 | throws IOException; | ||
| 121 | |||
| 122 | /** | ||
| 123 | * Invoked for a file in a directory. | ||
| 124 | * | ||
| 125 | * @param file | ||
| 126 | * a reference to the file | ||
| 127 | * @param attrs | ||
| 128 | * the file's basic attributes | ||
| 129 | * | ||
| 130 | * @return the visit result | ||
| 131 | * | ||
| 132 | * @throws IOException | ||
| 133 | * if an I/O error occurs | ||
| 134 | */ | ||
| 135 | FileVisitResult visitFile(T file, BasicFileAttributes attrs) | ||
| 136 | throws IOException; | ||
| 137 | |||
| 138 | /** | ||
| 139 | * Invoked for a file that could not be visited. This method is invoked | ||
| 140 | * if the file's attributes could not be read, the file is a directory | ||
| 141 | * that could not be opened, and other reasons. | ||
| 142 | * | ||
| 143 | * @param file | ||
| 144 | * a reference to the file | ||
| 145 | * @param exc | ||
| 146 | * the I/O exception that prevented the file from being visited | ||
| 147 | * | ||
| 148 | * @return the visit result | ||
| 149 | * | ||
| 150 | * @throws IOException | ||
| 151 | * if an I/O error occurs | ||
| 152 | */ | ||
| 153 | FileVisitResult visitFileFailed(T file, IOException exc) | ||
| 154 | throws IOException; | ||
| 155 | |||
| 156 | /** | ||
| 157 | * Invoked for a directory after entries in the directory, and all of their | ||
| 158 | * descendants, have been visited. This method is also invoked when iteration | ||
| 159 | * of the directory completes prematurely (by a {@link #visitFile visitFile} | ||
| 160 | * method returning {@link FileVisitResult#SKIP_SIBLINGS SKIP_SIBLINGS}, | ||
| 161 | * or an I/O error when iterating over the directory). | ||
| 162 | * | ||
| 163 | * @param dir | ||
| 164 | * a reference to the directory | ||
| 165 | * @param exc | ||
| 166 | * {@code null} if the iteration of the directory completes without | ||
| 167 | * an error; otherwise the I/O exception that caused the iteration | ||
| 168 | * of the directory to complete prematurely | ||
| 169 | * | ||
| 170 | * @return the visit result | ||
| 171 | * | ||
| 172 | * @throws IOException | ||
| 173 | * if an I/O error occurs | ||
| 174 | */ | ||
| 175 | FileVisitResult postVisitDirectory(T dir, IOException exc) | ||
| 176 | throws IOException; | ||
| 177 | } | ||