1 package de.japrost.jabudget.serialization;
2
3 import java.io.File;
4 import java.io.FileDescriptor;
5 import java.io.FileNotFoundException;
6 import java.io.FileOutputStream;
7 import java.io.IOException;
8 import java.io.OutputStream;
9 import java.nio.channels.FileChannel;
10
11 /**
12 * An {@link OutputStream} that uses a {@link FileOutputStream} internally, which is created when first access is done.
13 * On {@link OutputStream#close()} the internal {@link FileOutputStream} will be closed and unset that next writing will
14 * get a new stream.
15 */
16 //TODO move to a io project
17 public class LazyFileOutputStream extends OutputStream {
18
19 private final File file;
20 private FileOutputStream delegate;
21
22 /**
23 * Create an instance based on the given File.
24 *
25 * @param file the file to use in the internal delegate.
26 */
27 public LazyFileOutputStream(final File file) {
28 // TODO require non null
29 this.file = file;
30 }
31
32 /**
33 * {@inheritDoc}
34 * <p>
35 * <strong>This implementation</strong> calls {@link FileOutputStream#close()} on the delegate and unassigns the
36 * delegate.
37 */
38 @Override
39 public void close() throws IOException {
40 if (delegate != null) {
41 delegate.close();
42 delegate = null;
43 }
44 }
45
46 /**
47 * {@inheritDoc}
48 * <p>
49 * <strong>This implementation</strong> calls {@link FileOutputStream#flush()} on the delegate if it is initalized.
50 */
51 @Override
52 public void flush() throws IOException {
53 if (delegate != null) {
54 delegate.flush();
55 }
56 }
57
58 /**
59 * Initializes the delegate if not already done and delegates to {@link FileOutputStream#getChannel()}.
60 *
61 * @return {@link FileOutputStream#getChannel()}
62 * @throws FileNotFoundException if initialization of delegate fails. see
63 * {@link FileOutputStream#FileOutputStream(File)}.
64 */
65 public FileChannel getChannel() throws FileNotFoundException {
66 if (delegate == null) {
67 initDelegate();
68 }
69 return delegate.getChannel();
70 }
71
72 /**
73 * Initializes the delegate if not already done and delegates to {@link FileOutputStream#getFD()}.
74 *
75 * @return {@link FileOutputStream#getFD()}
76 * @throws IOException see {@link FileOutputStream#getFD()}.
77 * @throws FileNotFoundException if initialization of delegate fails. see
78 * {@link FileOutputStream#FileOutputStream(File)}.
79 */
80 public FileDescriptor getFD() throws IOException {
81 if (delegate == null) {
82 initDelegate();
83 }
84 return delegate.getFD();
85 }
86
87 /**
88 * {@inheritDoc}
89 * <p>
90 * <strong>This implementation</strong> innitializes the delegate if not already done and delegates to
91 * {@link FileOutputStream#write(byte[])}.
92 *
93 * @throws FileNotFoundException if initialization of delegate fails. see
94 * {@link FileOutputStream#FileOutputStream(File)}.
95 */
96 @Override
97 public void write(final byte[] b) throws IOException {
98 if (delegate == null) {
99 initDelegate();
100 }
101 delegate.write(b);
102 }
103
104 /**
105 * {@inheritDoc}
106 * <p>
107 * <strong>This implementation</strong> innitializes the delegate if not already done and delegates to
108 * {@link FileOutputStream#write(byte[], int, int)}.
109 *
110 * @throws FileNotFoundException if initialization of delegate fails. see
111 * {@link FileOutputStream#FileOutputStream(File)}.
112 */
113 @Override
114 public void write(final byte[] b, final int off, final int len) throws IOException {
115 if (delegate == null) {
116 initDelegate();
117 }
118 delegate.write(b, off, len);
119 }
120
121 /**
122 * {@inheritDoc}
123 * <p>
124 * <strong>This implementation</strong> innitializes the delegate if not already done and delegates to
125 * {@link FileOutputStream#write(int)}.
126 *
127 * @throws FileNotFoundException if initialization of delegate fails. see
128 * {@link FileOutputStream#FileOutputStream(File)}.
129 */
130 @Override
131 public void write(final int b) throws IOException {
132 if (delegate == null) {
133 initDelegate();
134 }
135 delegate.write(b);
136 }
137
138 /**
139 * Tell if the delegate is initialized.
140 *
141 * @return {@code true} if there is a delegate.
142 */
143 public boolean isOpen() {
144 return delegate != null;
145 }
146
147 private void initDelegate() throws FileNotFoundException {
148 delegate = new FileOutputStream(file);
149 }
150
151 }