/hudson-core/src/main/java/hudson/util/io/ReopenableFileOutputStream.java

 1/*
 2 * The MIT License
 3 *
 4 * Copyright (c) 2010, CloudBees, Inc.
 5 *
 6 * Permission is hereby granted, free of charge, to any person obtaining a copy
 7 * of this software and associated documentation files (the "Software"), to deal
 8 * in the Software without restriction, including without limitation the rights
 9 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
10 * copies of the Software, and to permit persons to whom the Software is
11 * furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
19 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
21 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
22 * THE SOFTWARE.
23 */
24package hudson.util.io;
25
26import hudson.util.IOException2;
27
28import java.io.File;
29import java.io.FileNotFoundException;
30import java.io.FileOutputStream;
31import java.io.IOException;
32import java.io.OutputStream;
33
34/**
35 * {@link OutputStream} that writes to a file.
36 *
37 * <p>
38 * Unlike regular {@link FileOutputStream}, this implementation allows the caller to close,
39 * and then keep writing.
40 *
41 * @author Kohsuke Kawaguchi
42 */
43public class ReopenableFileOutputStream extends OutputStream {
44    private final File out;
45
46    private OutputStream current;
47    private boolean appendOnNextOpen = false;
48
49    public ReopenableFileOutputStream(File out) {
50        this.out = out;
51    }
52
53    private synchronized OutputStream current() throws IOException {
54        if (current==null)
55            try {
56                current = new FileOutputStream(out,appendOnNextOpen);
57            } catch (FileNotFoundException e) {
58                throw new IOException2("Failed to open "+out,e);
59            }
60        return current;
61    }
62
63    @Override
64    public void write(int b) throws IOException {
65        current().write(b);
66    }
67
68    @Override
69    public void write(byte[] b) throws IOException {
70        current().write(b);
71    }
72
73    @Override
74    public void write(byte[] b, int off, int len) throws IOException {
75        current().write(b, off, len);
76    }
77
78    @Override
79    public void flush() throws IOException {
80        current().flush();
81    }
82
83    @Override
84    public synchronized void close() throws IOException {
85        if (current!=null) {
86            current.close();
87            appendOnNextOpen = true;
88            current = null;
89        }
90    }
91
92    /**
93     * In addition to close, ensure that the next "open" would truncate the file.
94     */
95    public synchronized void rewind() throws IOException {
96        close();
97        appendOnNextOpen = false;
98    }
99}