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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

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 * accompanied this code).

 *

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package javax.annotation.processing;

import javax.tools.JavaFileManager;

import javax.tools.*;

import javax.lang.model.element.Element;

import java.io.IOException;

/**

 * This interface supports the creation of new files by an annotation

 * processor.  Files created in this way will be known to the

 * annotation processing tool implementing this interface, better

 * enabling the tool to manage them.  Source and class files so

 * created will be {@linkplain RoundEnvironment#getRootElements

 * considered for processing} by the tool in a subsequent {@linkplain

 * RoundEnvironment round of processing} after the {@code close}

 * method has been called on the {@code Writer} or {@code

 * OutputStream} used to write the contents of the file.

 *

 * Three kinds of files are distinguished: source files, class files,

 * and auxiliary resource files.

 *

 * <p> There are two distinguished supported locations (subtrees

 * within the logical file system) where newly created files are

 * placed: one for {@linkplain

 * javax.tools.StandardLocation#SOURCE_OUTPUT new source files}, and

 * one for {@linkplain javax.tools.StandardLocation#CLASS_OUTPUT new

 * class files}.  (These might be specified on a tool's command line,

 * for example, using flags such as {@code -s} and {@code -d}.)  The

 * actual locations for new source files and new class files may or

 * may not be distinct on a particular run of the tool.  Resource

 * files may be created in either location.  The methods for reading

 * and writing resources take a relative name argument.  A relative

 * name is a non-null, non-empty sequence of path segments separated

 * by {@code '/'}; {@code '.'} and {@code '..'} are invalid path

 * segments.  A valid relative name must match the

 * &quot;path-rootless&quot; rule of <a

 * href="http://www.ietf.org/rfc/rfc3986.txt">RFC 3986</a>, section

 * 3.3.

 *

 * <p>The file creation methods take a variable number of arguments to

 * allow the <em>originating elements</em> to be provided as hints to

 * the tool infrastructure to better manage dependencies.  The

 * originating elements are the types or packages (representing {@code

 * attempt to create a new file.  For example, if an annotation

 * processor tries to create a source file, {@code

 * GeneratedFromUserSource}, in response to processing

 *

 * <blockquote><pre>

 *  @Generate

 *  public class UserSource {}

 * </pre></blockquote>

 *

 * the type element for {@code UserSource} should be passed as part of

 * the creation method call as in:

 *

 * <blockquote><pre>

 *      filer.createSourceFile("GeneratedFromUserSource",

 *                             eltUtils.getTypeElement("UserSource"));

 * </pre></blockquote>

 *

 * If there are no originating elements, none need to be passed.  This

 * information may be used in an incremental environment to determine

 * the need to rerun processors or remove generated files.

 * Non-incremental environments may ignore the originating element

 * information.

 *

 * <p> During each run of an annotation processing tool, a file with a

 * given pathname may be created only once.  If that file already

 * exists before the first attempt to create it, the old contents will

 * be deleted.  Any subsequent attempt to create the same file during

 * a run will throw a {@link FilerException}, as will attempting to

 * create both a class file and source file for the same type name or

 * same package name.  The {@linkplain Processor initial inputs} to

 * the tool are considered to be created by the zeroth round;

 * therefore, attempting to create a source or class file

 * corresponding to one of those inputs will result in a {@link

 * FilerException}.

 *

 * <p> In general, processors must not knowingly attempt to overwrite

 * existing files that were not generated by some processor.  A {@code

 * Filer} may reject attempts to open a file corresponding to an

 * existing type, like {@code java.lang.Object}.  Likewise, the

 * invoker of the annotation processing tool must not knowingly

 * configure the tool such that the discovered processors will attempt

 * to overwrite existing files that were not generated.

 *

 * <p> Processors can indicate a source or class file is generated by

 *

 * achieved by using a <i>decorator</i>-style pattern.  Instead of

 * modifying a class directly, the class is designed so that either

 * its superclass is generated by annotation processing or subclasses

 * of the class are generated by annotation processing.  If the

 * subclasses are generated, the parent class may be designed to use

 * factories instead of public constructors so that only subclass

 * instances would be presented to clients of the parent class.

 *

 * @author Joseph D. Darcy

 * @author Scott Seligman

 * @author Peter von der Ahé

 * @since 1.6

 */

public interface Filer {

    /**

     * Creates a new source file and returns an object to allow

     * package's name followed by {@code ".package-info"}; to create a

     * source file for an unnamed package, use {@code "package-info"}.

     *

     * java.nio.charset.Charset charset} to encode the contents of the

     * file, an {@code OutputStreamWriter} with the chosen charset can

     * be created from the {@code OutputStream} from the returned

     * object. If the {@code Writer} from the returned object is

     * directly used for writing, its charset is determined by the

     * implementation.  An annotation processing tool may have an

     * {@code -encoding} flag or analogous option for specifying this;

     * otherwise, it will typically be the platform's default

     * encoding.

     *

     * <p>To avoid subsequent errors, the contents of the source file

     * should be compatible with the {@linkplain

     * ProcessingEnvironment#getSourceVersion source version} being used

     * for this run.

     *

     * @param name  canonical (fully qualified) name of the principal type

     *          being declared in this file or a package name followed by

     *          {@code ".package-info"} for a package information file

     * associated with the creation of this file, may be elided or

     * {@code null}

     * @return a {@code JavaFileObject} to write the new source file

     * @throws FilerException if the same pathname has already been

     * created, the same type has already been created, or the name is

     * @throws IOException if the file cannot be created

     */

    JavaFileObject createSourceFile(CharSequence name,

                                    Element... originatingElements) throws IOException;

    /**

     * Creates a new class file, and returns an object to allow

     * package's name followed by {@code ".package-info"}; creating a

     * class file for an unnamed package is not supported.

     *

     *

     * @param name binary name of the type being written or a package name followed by

     *          {@code ".package-info"} for a package information file

     * associated with the creation of this file, may be elided or

     * {@code null}

     * @return a {@code JavaFileObject} to write the new class file

     * @throws FilerException if the same pathname has already been

     * created, the same type has already been created, or the name is

     * not valid for a type

     * @throws IOException if the file cannot be created

     */

    JavaFileObject createClassFile(CharSequence name,

                                   Element... originatingElements) throws IOException;

    /**

     * Creates a new auxiliary resource file for writing and returns a

     * file object for it.  The file may be located along with the

     * newly created source files, newly created binary files, or

     * other supported location.  The locations {@link

     * StandardLocation#CLASS_OUTPUT CLASS_OUTPUT} and {@link

     * StandardLocation#SOURCE_OUTPUT SOURCE_OUTPUT} must be

     *

     * annotation processing, even if the full pathname of the file

     * would correspond to the full pathname of a new source file

     * or new class file.

     *

     * @param location location of the new file

     * @param relativeName final pathname components of the file

     * @param originatingElements type or package elements causally

     * associated with the creation of this file, may be elided or

     * {@code null}

     * @return a {@code FileObject} to write the new resource

     * @throws IOException if the file cannot be created

     * @throws FilerException if the same pathname has already been

     * created

     * @throws IllegalArgumentException for an unsupported location

     * @throws IllegalArgumentException if {@code relativeName} is not relative

     */

   FileObject createResource(JavaFileManager.Location location,

                             CharSequence relativeName,

                             Element... originatingElements) throws IOException;

    /**

     * Returns an object for reading an existing resource.  The

     * locations {@link StandardLocation#CLASS_OUTPUT CLASS_OUTPUT}

     * and {@link StandardLocation#SOURCE_OUTPUT SOURCE_OUTPUT} must

     * be supported.

     *

     * @param location location of the file

     * @param relativeName final pathname components of the file

     * @return an object to read the file

     * @throws FilerException if the same pathname has already been

     * opened for writing

     * @throws IOException if the file cannot be opened

     * @throws IllegalArgumentException for an unsupported location

     * @throws IllegalArgumentException if {@code relativeName} is not relative

     */

    FileObject getResource(JavaFileManager.Location location,

                           CharSequence relativeName) throws IOException;

}