001 /*
002 * Copyright 2005-2006 Sun Microsystems, Inc. All Rights Reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation. Sun designates this
008 * particular file as subject to the "Classpath" exception as provided
009 * by Sun in the LICENSE file that accompanied this code.
010 *
011 * This code is distributed in the hope that it will be useful, but WITHOUT
012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014 * version 2 for more details (a copy is included in the LICENSE file that
015 * accompanied this code).
016 *
017 * You should have received a copy of the GNU General Public License version
018 * 2 along with this work; if not, write to the Free Software Foundation,
019 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020 *
021 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022 * CA 95054 USA or visit www.sun.com if you need additional information or
023 * have any questions.
024 */
025
026 package javax.annotation.processing;
027
028 import javax.tools.JavaFileManager;
029 import javax.tools.*;
030 import javax.lang.model.element.Element;
031 import java.io.IOException;
032
033 /**
034 * This interface supports the creation of new files by an annotation
035 * processor. Files created in this way will be known to the
036 * annotation processing tool implementing this interface, better
037 * enabling the tool to manage them. Source and class files so
038 * created will be considered for processing by the tool after the
039 * {@code close} method has been called on the {@code Writer} or
040 * {@code OutputStream} used to write the contents of the file.
041 *
042 * Three kinds of files are distinguished: source files, class files,
043 * and auxiliary resource files.
044 *
045 * <p> There are two distinguished supported locations (subtrees
046 * within the logical file system) where newly created files are
047 * placed: one for {@linkplain
048 * javax.tools.StandardLocation#SOURCE_OUTPUT new source files}, and
049 * one for {@linkplain javax.tools.StandardLocation#CLASS_OUTPUT new
050 * class files}. (These might be specified on a tool's command line,
051 * for example, using flags such as {@code -s} and {@code -d}.) The
052 * actual locations for new source files and new class files may or
053 * may not be distinct on a particular run of the tool. Resource
054 * files may be created in either location. The methods for reading
055 * and writing resources take a relative name argument. A relative
056 * name is a non-null, non-empty sequence of path segments separated
057 * by {@code '/'}; {@code '.'} and {@code '..'} are invalid path
058 * segments. A valid relative name must match the
059 * "path-rootless" rule of <a
060 * href="http://www.ietf.org/rfc/rfc3986.txt">RFC 3986</a>, section
061 * 3.3.
062 *
063 * <p>The file creation methods take a variable number of arguments to
064 * allow the <em>originating elements</em> to be provided as hints to
065 * the tool infrastructure to better manage dependencies. The
066 * originating elements are the types or packages (representing {@code
067 * package-info} files) which caused an annotation processor to
068 * attempt to create a new file. For example, if an annotation
069 * processor tries to create a source file, {@code
070 * GeneratedFromUserSource}, in response to processing
071 *
072 * <blockquote><pre>
073 * @Generate
074 * public class UserSource {}
075 * </pre></blockquote>
076 *
077 * the type element for {@code UserSource} should be passed as part of
078 * the creation method call as in:
079 *
080 * <blockquote><pre>
081 * filer.createSourceFile("GeneratedFromUserSource",
082 * eltUtils.getTypeElement("UserSource"));
083 * </pre></blockquote>
084 *
085 * If there are no originating elements, none need to be passed. This
086 * information may be used in an incremental environment to determine
087 * the need to rerun processors or remove generated files.
088 * Non-incremental environments may ignore the originating element
089 * information.
090 *
091 * <p> During each run of an annotation processing tool, a file with a
092 * given pathname may be created only once. If that file already
093 * exists before the first attempt to create it, the old contents will
094 * be deleted. Any subsequent attempt to create the same file during
095 * a run will throw a {@link FilerException}, as will attempting to
096 * create both a class file and source file for the same type name or
097 * same package name. The {@linkplain Processor initial inputs} to
098 * the tool are considered to be created by the zeroth round;
099 * therefore, attempting to create a source or class file
100 * corresponding to one of those inputs will result in a {@link
101 * FilerException}.
102 *
103 * <p> In general, processors must not knowingly attempt to overwrite
104 * existing files that were not generated by some processor. A {@code
105 * Filer} may reject attempts to open a file corresponding to an
106 * existing type, like {@code java.lang.Object}. Likewise, the
107 * invoker of the annotation processing tool must not knowingly
108 * configure the tool such that the discovered processors will attempt
109 * to overwrite existing files that were not generated.
110 *
111 * <p> Processors can indicate a source or class file is generated by
112 * including an {@link javax.annotation.Generated @Generated}
113 * annotation.
114 *
115 * <p> Note that some of the effect of overwriting a file can be
116 * achieved by using a <i>decorator</i>-style pattern. Instead of
117 * modifying a class directly, the class is designed so that either
118 * its superclass is generated by annotation processing or subclasses
119 * of the class are generated by annotation processing. If the
120 * subclasses are generated, the parent class may be designed to use
121 * factories instead of public constructors so that only subclass
122 * instances would be presented to clients of the parent class.
123 *
124 * @author Joseph D. Darcy
125 * @author Scott Seligman
126 * @author Peter von der Ahé
127 * @version 1.16 07/05/05
128 * @since 1.6
129 */
130 public interface Filer {
131 /**
132 * Creates a new source file and returns an object to allow
133 * writing to it. The file's name and path (relative to the
134 * {@linkplain StandardLocation#SOURCE_OUTPUT root output location
135 * for source files}) are based on the type to be declared in that
136 * file. If more than one type is being declared, the name of the
137 * principal top-level type (the public one, for example) should
138 * be used. A source file can also be created to hold information
139 * about a package, including package annotations. To create a
140 * source file for a named package, have {@code name} be the
141 * package's name followed by {@code ".package-info"}; to create a
142 * source file for an unnamed package, use {@code "package-info"}.
143 *
144 * <p> Note that to use a particular {@linkplain
145 * java.nio.charset.Charset charset} to encode the contents of the
146 * file, an {@code OutputStreamWriter} with the chosen charset can
147 * be created from the {@code OutputStream} from the returned
148 * object. If the {@code Writer} from the returned object is
149 * directly used for writing, its charset is determined by the
150 * implementation. An annotation processing tool may have an
151 * {@code -encoding} flag or analogous option for specifying this;
152 * otherwise, it will typically be the platform's default
153 * encoding.
154 *
155 * <p>To avoid subsequent errors, the contents of the source file
156 * should be compatible with the {@linkplain
157 * ProcessingEnvironment#getSourceVersion source version} being used
158 * for this run.
159 *
160 * @param name canonical (fully qualified) name of the principal type
161 * being declared in this file or a package name followed by
162 * {@code ".package-info"} for a package information file
163 * @param originatingElements type or package elements causally
164 * associated with the creation of this file, may be elided or
165 * {@code null}
166 * @return a {@code JavaFileObject} to write the new source file
167 * @throws FilerException if the same pathname has already been
168 * created, the same type has already been created, or the name is
169 * not valid for a type
170 * @throws IOException if the file cannot be created
171 */
172 JavaFileObject createSourceFile(CharSequence name,
173 Element... originatingElements) throws IOException;
174
175 /**
176 * Creates a new class file, and returns an object to allow
177 * writing to it. The file's name and path (relative to the
178 * {@linkplain StandardLocation#CLASS_OUTPUT root output location
179 * for class files}) are based on the name of the type being
180 * written. A class file can also be created to hold information
181 * about a package, including package annotations. To create a
182 * class file for a named package, have {@code name} be the
183 * package's name followed by {@code ".package-info"}; creating a
184 * class file for an unnamed package is not supported.
185 *
186 * <p>To avoid subsequent errors, the contents of the class file
187 * should be compatible with the {@linkplain
188 * ProcessingEnvironment#getSourceVersion source version} being used
189 * for this run.
190 *
191 * @param name binary name of the type being written or a package name followed by
192 * {@code ".package-info"} for a package information file
193 * @param originatingElements type or package elements causally
194 * associated with the creation of this file, may be elided or
195 * {@code null}
196 * @return a {@code JavaFileObject} to write the new class file
197 * @throws FilerException if the same pathname has already been
198 * created, the same type has already been created, or the name is
199 * not valid for a type
200 * @throws IOException if the file cannot be created
201 */
202 JavaFileObject createClassFile(CharSequence name,
203 Element... originatingElements) throws IOException;
204
205 /**
206 * Creates a new auxiliary resource file for writing and returns a
207 * file object for it. The file may be located along with the
208 * newly created source files, newly created binary files, or
209 * other supported location. The locations {@link
210 * StandardLocation#CLASS_OUTPUT CLASS_OUTPUT} and {@link
211 * StandardLocation#SOURCE_OUTPUT SOURCE_OUTPUT} must be
212 * supported. The resource may be named relative to some package
213 * (as are source and class files), and from there by a relative
214 * pathname. In a loose sense, the full pathname of the new file
215 * will be the concatenation of {@code location}, {@code pkg}, and
216 * {@code relativeName}.
217 *
218 * <p>Files created via this method are not registered for
219 * annotation processing, even if the full pathname of the file
220 * would correspond to the full pathname of a new source file
221 * or new class file.
222 *
223 * @param location location of the new file
224 * @param pkg package relative to which the file should be named,
225 * or the empty string if none
226 * @param relativeName final pathname components of the file
227 * @param originatingElements type or package elements causally
228 * associated with the creation of this file, may be elided or
229 * {@code null}
230 * @return a {@code FileObject} to write the new resource
231 * @throws IOException if the file cannot be created
232 * @throws FilerException if the same pathname has already been
233 * created
234 * @throws IllegalArgumentException for an unsupported location
235 * @throws IllegalArgumentException if {@code relativeName} is not relative
236 */
237 FileObject createResource(JavaFileManager.Location location,
238 CharSequence pkg, CharSequence relativeName,
239 Element... originatingElements) throws IOException;
240
241 /**
242 * Returns an object for reading an existing resource. The
243 * locations {@link StandardLocation#CLASS_OUTPUT CLASS_OUTPUT}
244 * and {@link StandardLocation#SOURCE_OUTPUT SOURCE_OUTPUT} must
245 * be supported.
246 *
247 * @param location location of the file
248 * @param pkg package relative to which the file should be searched,
249 * or the empty string if none
250 * @param relativeName final pathname components of the file
251 * @return an object to read the file
252 * @throws FilerException if the same pathname has already been
253 * opened for writing
254 * @throws IOException if the file cannot be opened
255 * @throws IllegalArgumentException for an unsupported location
256 * @throws IllegalArgumentException if {@code relativeName} is not relative
257 */
258 FileObject getResource(JavaFileManager.Location location,
259 CharSequence pkg, CharSequence relativeName)
260 throws IOException;
261 }
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