1 package org.eclipse.aether.util;
2
3 /*
4 * Licensed to the Apache Software Foundation (ASF) under one
5 * or more contributor license agreements. See the NOTICE file
6 * distributed with this work for additional information
7 * regarding copyright ownership. The ASF licenses this file
8 * to you under the Apache License, Version 2.0 (the
9 * "License"); you may not use this file except in compliance
10 * with the License. You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing,
15 * software distributed under the License is distributed on an
16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17 * KIND, either express or implied. See the License for the
18 * specific language governing permissions and limitations
19 * under the License.
20 */
21
22 import java.io.Closeable;
23 import java.io.IOException;
24 import java.nio.file.Files;
25 import java.nio.file.Path;
26 import java.nio.file.StandardCopyOption;
27
28 import static java.util.Objects.requireNonNull;
29
30 /**
31 * A utility class to write files.
32 *
33 * @since 1.9.0
34 */
35 public final class FileUtils
36 {
37 private FileUtils()
38 {
39 // hide constructor
40 }
41
42 /**
43 * A temporary file, that is removed when closed.
44 */
45 public interface TempFile extends Closeable
46 {
47 Path getPath();
48 }
49
50 /**
51 * Creates a {@link TempFile}. It will be in the default temporary-file directory. Returned instance should be
52 * handled in try-with-resource construct and created temp file is removed on close, if exists.
53 */
54 public static TempFile newTempFile() throws IOException
55 {
56 Path tempFile = Files.createTempFile( "resolver", "tmp" );
57 return new TempFile()
58 {
59 @Override
60 public Path getPath()
61 {
62 return tempFile;
63 }
64
65 @Override
66 public void close() throws IOException
67 {
68 Files.deleteIfExists( tempFile );
69 }
70 };
71 }
72
73 /**
74 * Creates a {@link TempFile} for given file. It will be in same directory where given file is, and will reuse its
75 * name for generated name. Returned instance should be handled in try-with-resource construct and created temp
76 * file is removed on close, if exists.
77 */
78 public static TempFile newTempFile( Path file ) throws IOException
79 {
80 requireNonNull( file.getParent(), "file must have parent" );
81 Path tempFile = Files.createTempFile( file.getParent(), file.getFileName().toString(), "tmp" );
82 return new TempFile()
83 {
84 @Override
85 public Path getPath()
86 {
87 return tempFile;
88 }
89
90 @Override
91 public void close() throws IOException
92 {
93 Files.deleteIfExists( tempFile );
94 }
95 };
96 }
97
98 /**
99 * A file writer, that accepts a {@link Path} to write some content to.
100 */
101 @FunctionalInterface
102 public interface FileWriter
103 {
104 void write( Path path ) throws IOException;
105 }
106
107 /**
108 * Writes file without backup.
109 *
110 * @param target that is the target file (must be file, the path must have parent).
111 * @param writer the writer that will accept a {@link Path} to write content to.
112 * @throws IOException if at any step IO problem occurs.
113 */
114 public static void writeFile( Path target, FileWriter writer ) throws IOException
115 {
116 writeFile( target, writer, false );
117 }
118
119 /**
120 * Writes file with backup copy (appends ".bak" extension).
121 *
122 * @param target that is the target file (must be file, the path must have parent).
123 * @param writer the writer that will accept a {@link Path} to write content to.
124 * @throws IOException if at any step IO problem occurs.
125 */
126 public static void writeFileWithBackup( Path target, FileWriter writer ) throws IOException
127 {
128 writeFile( target, writer, true );
129 }
130
131 /**
132 * Utility method to write out file to disk in "atomic" manner, with optional backups (".bak") if needed. This
133 * ensures that no other thread or process will be able to read not fully written files. Finally, this methos
134 * may create the needed parent directories, if the passed in target parents does not exist.
135 *
136 * @param target that is the target file (must be an existing or non-existing file, the path must have parent).
137 * @param writer the writer that will accept a {@link Path} to write content to.
138 * @param doBackup if {@code true}, and target file is about to be overwritten, a ".bak" file with old contents will
139 * be created/overwritten.
140 * @throws IOException if at any step IO problem occurs.
141 */
142 private static void writeFile( Path target, FileWriter writer, boolean doBackup ) throws IOException
143 {
144 requireNonNull( target, "target is null" );
145 requireNonNull( writer, "writer is null" );
146 Path parent = requireNonNull( target.getParent(), "target must have parent" );
147 Path temp = null;
148
149 Files.createDirectories( parent );
150 try
151 {
152 temp = Files.createTempFile( parent, "writer", "tmp" );
153 writer.write( temp );
154 if ( doBackup && Files.isRegularFile( target ) )
155 {
156 Files.copy( target, parent.resolve( target.getFileName() + ".bak" ),
157 StandardCopyOption.REPLACE_EXISTING );
158 }
159 Files.move( temp, target, StandardCopyOption.ATOMIC_MOVE );
160 }
161 finally
162 {
163 if ( temp != null )
164 {
165 Files.deleteIfExists( temp );
166 }
167 }
168 }
169 }