1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18
19 package org.apache.tomcat.util.http.fileupload;
20
21 import java.io.ByteArrayOutputStream;
22 import java.io.File;
23 import java.io.FileOutputStream;
24 import java.io.IOException;
25 import java.io.OutputStream;
26
27 /**
28 * <p>An output stream which will retain data in memory until a specified
29 * threshold is reached, and only then commit it to disk. If the stream is
30 * closed before the threshold is reached, the data will not be written to
31 * disk at all.</p>
32 *
33 * @author <a href="mailto:martinc@apache.org">Martin Cooper</a>
34 *
35 * @version $Id: DeferredFileOutputStream.java 711597 2008-11-05 16:09:26Z markt $
36 */
37 public class DeferredFileOutputStream
38 extends ThresholdingOutputStream
39 {
40
41 // ----------------------------------------------------------- Data members
42
43
44 /**
45 * The output stream to which data will be written prior to the theshold
46 * being reached.
47 */
48 private ByteArrayOutputStream memoryOutputStream;
49
50
51 /**
52 * The output stream to which data will be written after the theshold is
53 * reached.
54 */
55 private FileOutputStream diskOutputStream;
56
57
58 /**
59 * The output stream to which data will be written at any given time. This
60 * will always be one of <code>memoryOutputStream</code> or
61 * <code>diskOutputStream</code>.
62 */
63 private OutputStream currentOutputStream;
64
65
66 /**
67 * The file to which output will be directed if the threshold is exceeded.
68 */
69 private File outputFile;
70
71
72 // ----------------------------------------------------------- Constructors
73
74
75 /**
76 * Constructs an instance of this class which will trigger an event at the
77 * specified threshold, and save data to a file beyond that point.
78 *
79 * @param threshold The number of bytes at which to trigger an event.
80 * @param outputFile The file to which data is saved beyond the threshold.
81 */
82 public DeferredFileOutputStream(int threshold, File outputFile)
83 {
84 super(threshold);
85 this.outputFile = outputFile;
86
87 if (threshold < DefaultFileItemFactory.DEFAULT_SIZE_THRESHOLD) {
88 // Small threshold, use it
89 memoryOutputStream = new ByteArrayOutputStream(threshold);
90 } else {
91 // Large threshold. Use default and array will expand if required
92 memoryOutputStream = new ByteArrayOutputStream(
93 DefaultFileItemFactory.DEFAULT_SIZE_THRESHOLD);
94 }
95 currentOutputStream = memoryOutputStream;
96 }
97
98
99 // --------------------------------------- ThresholdingOutputStream methods
100
101
102 /**
103 * Returns the current output stream. This may be memory based or disk
104 * based, depending on the current state with respect to the threshold.
105 *
106 * @return The underlying output stream.
107 *
108 * @exception IOException if an error occurs.
109 */
110 protected OutputStream getStream() throws IOException
111 {
112 return currentOutputStream;
113 }
114
115
116 /**
117 * Switches the underlying output stream from a memory based stream to one
118 * that is backed by disk. This is the point at which we realise that too
119 * much data is being written to keep in memory, so we elect to switch to
120 * disk-based storage.
121 *
122 * @exception IOException if an error occurs.
123 */
124 protected void thresholdReached() throws IOException
125 {
126 byte[] data = memoryOutputStream.toByteArray();
127 FileOutputStream fos = new FileOutputStream(outputFile);
128 fos.write(data);
129 diskOutputStream = fos;
130 currentOutputStream = fos;
131 memoryOutputStream = null;
132 }
133
134
135 // --------------------------------------------------------- Public methods
136
137
138 /**
139 * Determines whether or not the data for this output stream has been
140 * retained in memory.
141 *
142 * @return <code>true</code> if the data is available in memory;
143 * <code>false</code> otherwise.
144 */
145 public boolean isInMemory()
146 {
147 return (!isThresholdExceeded());
148 }
149
150
151 /**
152 * Returns the data for this output stream as an array of bytes, assuming
153 * that the data has been retained in memory. If the data was written to
154 * disk, this method returns <code>null</code>.
155 *
156 * @return The data for this output stream, or <code>null</code> if no such
157 * data is available.
158 */
159 public byte[] getData()
160 {
161 if (memoryOutputStream != null)
162 {
163 return memoryOutputStream.toByteArray();
164 }
165 return null;
166 }
167
168
169 /**
170 * Returns the data for this output stream as a <code>File</code>, assuming
171 * that the data was written to disk. If the data was retained in memory,
172 * this method returns <code>null</code>.
173 *
174 * @return The file for this output stream, or <code>null</code> if no such
175 * file exists.
176 */
177 public File getFile()
178 {
179 return outputFile;
180 }
181 }