1 /* 2 * Copyright (c) 2005, 2006, 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.annotation.processing; 27 28 import javax.tools.JavaFileManager; 29 import javax.tools.*; 30 import javax.lang.model.element.Element; 31 import java.io.IOException; 32 33 /** 34 * This interface supports the creation of new files by an annotation 35 * processor. Files created in this way will be known to the 36 * annotation processing tool implementing this interface, better 37 * enabling the tool to manage them. Source and class files so 38 * created will be {@linkplain RoundEnvironment#getRootElements 39 * considered for processing} by the tool in a subsequent {@linkplain 40 * RoundEnvironment round of processing} after the {@code close} 41 * method has been called on the {@code Writer} or {@code 42 * OutputStream} used to write the contents of the file. 43 * 44 * Three kinds of files are distinguished: source files, class files, 45 * and auxiliary resource files. 46 * 47 * <p> There are two distinguished supported locations (subtrees 48 * within the logical file system) where newly created files are 49 * placed: one for {@linkplain 50 * javax.tools.StandardLocation#SOURCE_OUTPUT new source files}, and 51 * one for {@linkplain javax.tools.StandardLocation#CLASS_OUTPUT new 52 * class files}. (These might be specified on a tool's command line, 53 * for example, using flags such as {@code -s} and {@code -d}.) The 54 * actual locations for new source files and new class files may or 55 * may not be distinct on a particular run of the tool. Resource 56 * files may be created in either location. The methods for reading 57 * and writing resources take a relative name argument. A relative 58 * name is a non-null, non-empty sequence of path segments separated 59 * by {@code '/'}; {@code '.'} and {@code '..'} are invalid path 60 * segments. A valid relative name must match the 61 * "path-rootless" rule of <a 62 * href="http://www.ietf.org/rfc/rfc3986.txt">RFC 3986</a>, section 63 * 3.3. 64 * 65 * <p>The file creation methods take a variable number of arguments to 66 * allow the <em>originating elements</em> to be provided as hints to 67 * the tool infrastructure to better manage dependencies. The 68 * originating elements are the types or packages (representing {@code 69 * package-info} files) which caused an annotation processor to 70 * attempt to create a new file. For example, if an annotation 71 * processor tries to create a source file, {@code 72 * GeneratedFromUserSource}, in response to processing 73 * 74 * <blockquote><pre> 75 * @Generate 76 * public class UserSource {} 77 * </pre></blockquote> 78 * 79 * the type element for {@code UserSource} should be passed as part of 80 * the creation method call as in: 81 * 82 * <blockquote><pre> 83 * filer.createSourceFile("GeneratedFromUserSource", 84 * eltUtils.getTypeElement("UserSource")); 85 * </pre></blockquote> 86 * 87 * If there are no originating elements, none need to be passed. This 88 * information may be used in an incremental environment to determine 89 * the need to rerun processors or remove generated files. 90 * Non-incremental environments may ignore the originating element 91 * information. 92 * 93 * <p> During each run of an annotation processing tool, a file with a 94 * given pathname may be created only once. If that file already 95 * exists before the first attempt to create it, the old contents will 96 * be deleted. Any subsequent attempt to create the same file during 97 * a run will throw a {@link FilerException}, as will attempting to 98 * create both a class file and source file for the same type name or 99 * same package name. The {@linkplain Processor initial inputs} to 100 * the tool are considered to be created by the zeroth round; 101 * therefore, attempting to create a source or class file 102 * corresponding to one of those inputs will result in a {@link 103 * FilerException}. 104 * 105 * <p> In general, processors must not knowingly attempt to overwrite 106 * existing files that were not generated by some processor. A {@code 107 * Filer} may reject attempts to open a file corresponding to an 108 * existing type, like {@code java.lang.Object}. Likewise, the 109 * invoker of the annotation processing tool must not knowingly 110 * configure the tool such that the discovered processors will attempt 111 * to overwrite existing files that were not generated. 112 * 113 * <p> Processors can indicate a source or class file is generated by 114 * including an {@link javax.annotation.Generated @Generated} 115 * annotation. 116 * 117 * <p> Note that some of the effect of overwriting a file can be 118 * achieved by using a <i>decorator</i>-style pattern. Instead of 119 * modifying a class directly, the class is designed so that either 120 * its superclass is generated by annotation processing or subclasses 121 * of the class are generated by annotation processing. If the 122 * subclasses are generated, the parent class may be designed to use 123 * factories instead of public constructors so that only subclass 124 * instances would be presented to clients of the parent class. 125 * 126 * @author Joseph D. Darcy 127 * @author Scott Seligman 128 * @author Peter von der Ahé 129 * @since 1.6 130 */ 131 public interface Filer { 132 /** 133 * Creates a new source file and returns an object to allow 134 * writing to it. The file's name and path (relative to the 135 * {@linkplain StandardLocation#SOURCE_OUTPUT root output location 136 * for source files}) are based on the type to be declared in that 137 * file. If more than one type is being declared, the name of the 138 * principal top-level type (the public one, for example) should 139 * be used. A source file can also be created to hold information 140 * about a package, including package annotations. To create a 141 * source file for a named package, have {@code name} be the 142 * package's name followed by {@code ".package-info"}; to create a 143 * source file for an unnamed package, use {@code "package-info"}. 144 * 145 * <p> Note that to use a particular {@linkplain 146 * java.nio.charset.Charset charset} to encode the contents of the 147 * file, an {@code OutputStreamWriter} with the chosen charset can 148 * be created from the {@code OutputStream} from the returned 149 * object. If the {@code Writer} from the returned object is 150 * directly used for writing, its charset is determined by the 151 * implementation. An annotation processing tool may have an 152 * {@code -encoding} flag or analogous option for specifying this; 153 * otherwise, it will typically be the platform's default 154 * encoding. 155 * 156 * <p>To avoid subsequent errors, the contents of the source file 157 * should be compatible with the {@linkplain 158 * ProcessingEnvironment#getSourceVersion source version} being used 159 * for this run. 160 * 161 * @param name canonical (fully qualified) name of the principal type 162 * being declared in this file or a package name followed by 163 * {@code ".package-info"} for a package information file 164 * @param originatingElements type or package elements causally 165 * associated with the creation of this file, may be elided or 166 * {@code null} 167 * @return a {@code JavaFileObject} to write the new source file 168 * @throws FilerException if the same pathname has already been 169 * created, the same type has already been created, or the name is 170 * not valid for a type 171 * @throws IOException if the file cannot be created 172 */ 173 JavaFileObject createSourceFile(CharSequence name, 174 Element... originatingElements) throws IOException; 175 176 /** 177 * Creates a new class file, and returns an object to allow 178 * writing to it. The file's name and path (relative to the 179 * {@linkplain StandardLocation#CLASS_OUTPUT root output location 180 * for class files}) are based on the name of the type being 181 * written. A class file can also be created to hold information 182 * about a package, including package annotations. To create a 183 * class file for a named package, have {@code name} be the 184 * package's name followed by {@code ".package-info"}; creating a 185 * class file for an unnamed package is not supported. 186 * 187 * <p>To avoid subsequent errors, the contents of the class file 188 * should be compatible with the {@linkplain 189 * ProcessingEnvironment#getSourceVersion source version} being used 190 * for this run. 191 * 192 * @param name binary name of the type being written or a package name followed by 193 * {@code ".package-info"} for a package information file 194 * @param originatingElements type or package elements causally 195 * associated with the creation of this file, may be elided or 196 * {@code null} 197 * @return a {@code JavaFileObject} to write the new class file 198 * @throws FilerException if the same pathname has already been 199 * created, the same type has already been created, or the name is 200 * not valid for a type 201 * @throws IOException if the file cannot be created 202 */ 203 JavaFileObject createClassFile(CharSequence name, 204 Element... originatingElements) throws IOException; 205 206 /** 207 * Creates a new auxiliary resource file for writing and returns a 208 * file object for it. The file may be located along with the 209 * newly created source files, newly created binary files, or 210 * other supported location. The locations {@link 211 * StandardLocation#CLASS_OUTPUT CLASS_OUTPUT} and {@link 212 * StandardLocation#SOURCE_OUTPUT SOURCE_OUTPUT} must be 213 * supported. The resource may be named relative to some package 214 * (as are source and class files), and from there by a relative 215 * pathname. In a loose sense, the full pathname of the new file 216 * will be the concatenation of {@code location}, {@code pkg}, and 217 * {@code relativeName}. 218 * 219 * <p>Files created via this method are not registered for 220 * annotation processing, even if the full pathname of the file 221 * would correspond to the full pathname of a new source file 222 * or new class file. 223 * 224 * @param location location of the new file 225 * @param pkg package relative to which the file should be named, 226 * or the empty string if none 227 * @param relativeName final pathname components of the file 228 * @param originatingElements type or package elements causally 229 * associated with the creation of this file, may be elided or 230 * {@code null} 231 * @return a {@code FileObject} to write the new resource 232 * @throws IOException if the file cannot be created 233 * @throws FilerException if the same pathname has already been 234 * created 235 * @throws IllegalArgumentException for an unsupported location 236 * @throws IllegalArgumentException if {@code relativeName} is not relative 237 */ 238 FileObject createResource(JavaFileManager.Location location, 239 CharSequence pkg, 240 CharSequence relativeName, 241 Element... originatingElements) throws IOException; 242 243 /** 244 * Returns an object for reading an existing resource. The 245 * locations {@link StandardLocation#CLASS_OUTPUT CLASS_OUTPUT} 246 * and {@link StandardLocation#SOURCE_OUTPUT SOURCE_OUTPUT} must 247 * be supported. 248 * 249 * @param location location of the file 250 * @param pkg package relative to which the file should be searched, 251 * or the empty string if none 252 * @param relativeName final pathname components of the file 253 * @return an object to read the file 254 * @throws FilerException if the same pathname has already been 255 * opened for writing 256 * @throws IOException if the file cannot be opened 257 * @throws IllegalArgumentException for an unsupported location 258 * @throws IllegalArgumentException if {@code relativeName} is not relative 259 */ 260 FileObject getResource(JavaFileManager.Location location, 261 CharSequence pkg, 262 CharSequence relativeName) throws IOException; 263 }