J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 2000-2004 Sun Microsystems, Inc. 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. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any questions. |
| 24 | */ |
| 25 | |
| 26 | package javax.imageio.spi; |
| 27 | |
| 28 | import java.io.File; |
| 29 | import java.io.IOException; |
| 30 | import javax.imageio.stream.ImageInputStream; |
| 31 | |
| 32 | /** |
| 33 | * The service provider interface (SPI) for |
| 34 | * <code>ImageInputStream</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>ImageInputStream</code>. For example, |
| 40 | * a particular <code>ImageInputStreamSpi</code> might allow |
| 41 | * a generic <code>InputStream</code> to be used as an input source; |
| 42 | * another might take input from a <code>URL</code>. |
| 43 | * |
| 44 | * <p> By treating the creation of <code>ImageInputStream</code>s as a |
| 45 | * pluggable service, it becomes possible to handle future input |
| 46 | * sources without changing the API. Also, high-performance |
| 47 | * implementations of <code>ImageInputStream</code> (for example, |
| 48 | * native implementations for a particular platform) can be installed |
| 49 | * and used transparently by applications. |
| 50 | * |
| 51 | * @see IIORegistry |
| 52 | * @see javax.imageio.stream.ImageInputStream |
| 53 | * |
| 54 | */ |
| 55 | public abstract class ImageInputStreamSpi extends IIOServiceProvider { |
| 56 | |
| 57 | /** |
| 58 | * A <code>Class</code> object indicating the legal object type |
| 59 | * for use by the <code>createInputStreamInstance</code> method. |
| 60 | */ |
| 61 | protected Class<?> inputClass; |
| 62 | |
| 63 | /** |
| 64 | * Constructs a blank <code>ImageInputStreamSpi</code>. It is up |
| 65 | * to the subclass to initialize instance variables and/or |
| 66 | * override method implementations in order to provide working |
| 67 | * versions of all methods. |
| 68 | */ |
| 69 | protected ImageInputStreamSpi() { |
| 70 | } |
| 71 | |
| 72 | /** |
| 73 | * Constructs an <code>ImageInputStreamSpi</code> with a given set |
| 74 | * of values. |
| 75 | * |
| 76 | * @param vendorName the vendor name. |
| 77 | * @param version a version identifier. |
| 78 | * @param inputClass a <code>Class</code> object indicating the |
| 79 | * legal object type for use by the |
| 80 | * <code>createInputStreamInstance</code> method. |
| 81 | * |
| 82 | * @exception IllegalArgumentException if <code>vendorName</code> |
| 83 | * is <code>null</code>. |
| 84 | * @exception IllegalArgumentException if <code>version</code> |
| 85 | * is <code>null</code>. |
| 86 | */ |
| 87 | public ImageInputStreamSpi(String vendorName, |
| 88 | String version, |
| 89 | Class<?> inputClass) { |
| 90 | super(vendorName, version); |
| 91 | this.inputClass = inputClass; |
| 92 | } |
| 93 | |
| 94 | /** |
| 95 | * Returns a <code>Class</code> object representing the class or |
| 96 | * interface type that must be implemented by an input source in |
| 97 | * order to be "wrapped" in an <code>ImageInputStream</code> via |
| 98 | * the <code>createInputStreamInstance</code> method. |
| 99 | * |
| 100 | * <p> Typical return values might include |
| 101 | * <code>InputStream.class</code> or <code>URL.class</code>, but |
| 102 | * any class may be used. |
| 103 | * |
| 104 | * @return a <code>Class</code> variable. |
| 105 | * |
| 106 | * @see #createInputStreamInstance(Object, boolean, File) |
| 107 | */ |
| 108 | public Class<?> getInputClass() { |
| 109 | return inputClass; |
| 110 | } |
| 111 | |
| 112 | /** |
| 113 | * Returns <code>true</code> if the <code>ImageInputStream</code> |
| 114 | * implementation associated with this service provider can |
| 115 | * optionally make use of a cache file for improved performance |
| 116 | * and/or memory footrprint. If <code>false</code>, the value of |
| 117 | * the <code>useCache</code> argument to |
| 118 | * <code>createInputStreamInstance</code> will be ignored. |
| 119 | * |
| 120 | * <p> The default implementation returns <code>false</code>. |
| 121 | * |
| 122 | * @return <code>true</code> if a cache file can be used by the |
| 123 | * input streams created by this service provider. |
| 124 | */ |
| 125 | public boolean canUseCacheFile() { |
| 126 | return false; |
| 127 | } |
| 128 | |
| 129 | /** |
| 130 | * Returns <code>true</code> if the <code>ImageInputStream</code> |
| 131 | * implementation associated with this service provider requires |
| 132 | * the use of a cache <code>File</code>. If <code>true</code>, |
| 133 | * the value of the <code>useCache</code> argument to |
| 134 | * <code>createInputStreamInstance</code> will be ignored. |
| 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 | * input streams created by this service provider. |
| 140 | */ |
| 141 | public boolean needsCacheFile() { |
| 142 | return false; |
| 143 | } |
| 144 | |
| 145 | /** |
| 146 | * Returns an instance of the <code>ImageInputStream</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 input an object of the class type returned by |
| 153 | * <code>getInputClass</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>ImageInputStream</code> instance. |
| 161 | * |
| 162 | * @exception IllegalArgumentException if <code>input</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 #getInputClass |
| 171 | * @see #canUseCacheFile |
| 172 | * @see #needsCacheFile |
| 173 | */ |
| 174 | public abstract ImageInputStream |
| 175 | createInputStreamInstance(Object input, |
| 176 | boolean useCache, |
| 177 | File cacheDir) throws IOException; |
| 178 | |
| 179 | /** |
| 180 | * Returns an instance of the <code>ImageInputStream</code> |
| 181 | * implementation associated with this service provider. A cache |
| 182 | * file will be created in the system-dependent default |
| 183 | * temporary-file directory, if needed. |
| 184 | * |
| 185 | * @param input an object of the class type returned by |
| 186 | * <code>getInputClass</code>. |
| 187 | * |
| 188 | * @return an <code>ImageInputStream</code> instance. |
| 189 | * |
| 190 | * @exception IllegalArgumentException if <code>input</code> is |
| 191 | * not an instance of the correct class or is <code>null</code>. |
| 192 | * @exception IOException if a cache file is needed but cannot be |
| 193 | * created. |
| 194 | * |
| 195 | * @see #getInputClass() |
| 196 | */ |
| 197 | public ImageInputStream createInputStreamInstance(Object input) |
| 198 | throws IOException { |
| 199 | return createInputStreamInstance(input, true, null); |
| 200 | } |
| 201 | } |