1 /*
2 * Copyright (c) 2000, 2004, 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 javax.imageio.spi;
27
28 import java.io.File;
29 import java.io.IOException;
30 import javax.imageio.stream.ImageOutputStream;
31
32 /**
33 * The service provider interface (SPI) for
34 * <code>ImageOutputStream</code>s. For more information on service
35 * provider interfaces, see the class comment for the
36 * <code>IIORegistry</code> class.
37 *
38 * <p> This interface allows arbitrary objects to be "wrapped" by
39 * instances of <code>ImageOutputStream</code>. For example, a
40 * particular <code>ImageOutputStreamSpi</code> might allow a generic
41 * <code>OutputStream</code> to be used as a destination; another
42 * might output to a <code>File</code> or to a device such as a serial
43 * port.
44 *
45 * <p> By treating the creation of <code>ImageOutputStream</code>s as
46 * a pluggable service, it becomes possible to handle future output
47 * destinations without changing the API. Also, high-performance
48 * implementations of <code>ImageOutputStream</code> (for example,
49 * native implementations for a particular platform) can be installed
50 * and used transparently by applications.
51 *
52 * @see IIORegistry
53 * @see javax.imageio.stream.ImageOutputStream
54 *
55 */
56 public abstract class ImageOutputStreamSpi extends IIOServiceProvider {
57
58 /**
59 * A <code>Class</code> object indicating the legal object type
60 * for use by the <code>createInputStreamInstance</code> method.
61 */
62 protected Class<?> outputClass;
63
64 /**
65 * Constructs a blank <code>ImageOutputStreamSpi</code>. It is up
66 * to the subclass to initialize instance variables and/or
67 * override method implementations in order to provide working
68 * versions of all methods.
69 */
70 protected ImageOutputStreamSpi() {
71 }
72
73 /**
74 * Constructs an <code>ImageOutputStreamSpi</code> with a given
75 * set of values.
76 *
77 * @param vendorName the vendor name.
78 * @param version a version identifier.
79 * @param outputClass a <code>Class</code> object indicating the
80 * legal object type for use by the
81 * <code>createOutputStreamInstance</code> method.
82 *
83 * @exception IllegalArgumentException if <code>vendorName</code>
84 * is <code>null</code>.
85 * @exception IllegalArgumentException if <code>version</code>
86 * is <code>null</code>.
87 */
88 public ImageOutputStreamSpi(String vendorName,
89 String version,
90 Class<?> outputClass) {
91 super(vendorName, version);
92 this.outputClass = outputClass;
93 }
94
95 /**
96 * Returns a <code>Class</code> object representing the class or
97 * interface type that must be implemented by an output
98 * destination in order to be "wrapped" in an
99 * <code>ImageOutputStream</code> via the
100 * <code>createOutputStreamInstance</code> method.
101 *
102 * <p> Typical return values might include
103 * <code>OutputStream.class</code> or <code>File.class</code>, but
104 * any class may be used.
105 *
106 * @return a <code>Class</code> variable.
107 *
108 * @see #createOutputStreamInstance(Object, boolean, File)
109 */
110 public Class<?> getOutputClass() {
111 return outputClass;
112 }
113
114 /**
115 * Returns <code>true</code> if the <code>ImageOutputStream</code>
116 * implementation associated with this service provider can
117 * optionally make use of a cache <code>File</code> for improved
118 * performance and/or memory footrprint. If <code>false</code>,
119 * the value of the <code>cacheFile</code> argument to
120 * <code>createOutputStreamInstance</code> will be ignored.
121 *
122 * <p> The default implementation returns <code>false</code>.
123 *
124 * @return <code>true</code> if a cache file can be used by the
125 * output streams created by this service provider.
126 */
127 public boolean canUseCacheFile() {
128 return false;
129 }
130
131 /**
132 * Returns <code>true</code> if the <code>ImageOutputStream</code>
133 * implementation associated with this service provider requires
134 * the use of a cache <code>File</code>.
135 *
136 * <p> The default implementation returns <code>false</code>.
137 *
138 * @return <code>true</code> if a cache file is needed by the
139 * output streams created by this service provider.
140 */
141 public boolean needsCacheFile() {
142 return false;
143 }
144
145 /**
146 * Returns an instance of the <code>ImageOutputStream</code>
147 * implementation associated with this service provider. If the
148 * use of a cache file is optional, the <code>useCache</code>
149 * parameter will be consulted. Where a cache is required, or
150 * not applicable, the value of <code>useCache</code> will be ignored.
151 *
152 * @param output an object of the class type returned by
153 * <code>getOutputClass</code>.
154 * @param useCache a <code>boolean</code> indicating whether a
155 * cache file should be used, in cases where it is optional.
156 * @param cacheDir a <code>File</code> indicating where the
157 * cache file should be created, or <code>null</code> to use the
158 * system directory.
159 *
160 * @return an <code>ImageOutputStream</code> instance.
161 *
162 * @exception IllegalArgumentException if <code>output</code> is
163 * not an instance of the correct class or is <code>null</code>.
164 * @exception IllegalArgumentException if a cache file is needed,
165 * but <code>cacheDir</code> is non-<code>null</code> and is not a
166 * directory.
167 * @exception IOException if a cache file is needed but cannot be
168 * created.
169 *
170 * @see #getOutputClass
171 */
172 public abstract
173 ImageOutputStream createOutputStreamInstance(Object output,
174 boolean useCache,
175 File cacheDir)
176 throws IOException;
177
178 /**
179 * Returns an instance of the <code>ImageOutputStream</code>
180 * implementation associated with this service provider. A cache
181 * file will be created in the system-dependent default
182 * temporary-file directory, if needed.
183 *
184 * @param output an object of the class type returned by
185 * <code>getOutputClass</code>.
186 *
187 * @return an <code>ImageOutputStream</code> instance.
188 *
189 * @exception IllegalArgumentException if <code>output</code> is
190 * not an instance of the correct class or is <code>null</code>.
191 * @exception IOException if a cache file is needed but cannot be
192 * created.
193 *
194 * @see #getOutputClass()
195 */
196 public ImageOutputStream createOutputStreamInstance(Object output)
197 throws IOException {
198 return createOutputStreamInstance(output, true, null);
199 }
200 }