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package javax.tools;

import java.io.Writer;

import java.nio.charset.Charset;

import java.util.Locale;

import java.util.concurrent.Callable;

import javax.annotation.processing.Processor;

/**

 * Interface to invoke Java™ programming language compilers from

 * programs.

 *

 * <p>The compiler might generate diagnostics during compilation (for

 * example, error messages).  If a diagnostic listener is provided,

 * the diagnostics will be supplied to the listener.  If no listener

 * is provided, the diagnostics will be formatted in an unspecified

 * format and written to the default output, which is {@code

 * System.err} unless otherwise specified.  Even if a diagnostic

 * listener is supplied, some diagnostics might not fit in a {@code

 * Diagnostic} and will be written to the default output.

 *

 * <p>A compiler tool has an associated standard file manager, which

 * is the file manager that is native to the tool (or built-in).  The

 * standard file manager can be obtained by calling {@linkplain

 * #getStandardFileManager getStandardFileManager}.

 *

 * <p>A compiler tool must function with any file manager as long as

 * any additional requirements as detailed in the methods below are

 * met.  If no file manager is provided, the compiler tool will use a

 * standard file manager such as the one returned by {@linkplain

 * #getStandardFileManager getStandardFileManager}.

 *

 * <p>An instance implementing this interface must conform to

 * <cite>The Java&trade; Language Specification</cite>

 * and generate class files conforming to

 * <cite>The Java&trade; Virtual Machine Specification</cite>.

 * The versions of these

 * specifications are defined in the {@linkplain Tool} interface.

 *

 * Additionally, an instance of this interface supporting {@link

 * javax.lang.model.SourceVersion#RELEASE_6 SourceVersion.RELEASE_6}

 * or higher must also support {@linkplain javax.annotation.processing

 * annotation processing}.

 *

 * <p>The compiler relies on two services: {@linkplain

 * DiagnosticListener diagnostic listener} and {@linkplain

 * JavaFileManager file manager}.  Although most classes and

 * interfaces in this package defines an API for compilers (and

 * tools in general) the interfaces {@linkplain DiagnosticListener},

 * {@linkplain JavaFileManager}, {@linkplain FileObject}, and

 * {@linkplain JavaFileObject} are not intended to be used in

 * applications.  Instead these interfaces are intended to be

 * implemented and used to provide customized services for a

 * compiler and thus defines an SPI for compilers.

 *

 * <p>There are a number of classes and interfaces in this package

 * which are designed to ease the implementation of the SPI to

 * customize the behavior of a compiler:

 *

 * <dl>

 *   <dt>{@link StandardJavaFileManager}</dt>

 *   <dd>

 *

 *     Every compiler which implements this interface provides a

 *     standard file manager for operating on regular {@linkplain

 *     java.io.File files}.  The StandardJavaFileManager interface

 *     defines additional methods for creating file objects from

 *     regular files.

 *

 *     <p>The standard file manager serves two purposes:

 *

 *     <ul>

 *       <li>basic building block for customizing how a compiler reads

 *       and writes files</li>

 *       <li>sharing between multiple compilation tasks</li>

 *     </ul>

 *

 *     <p>Reusing a file manager can potentially reduce overhead of

 *     scanning the file system and reading jar files.  Although there

 *     might be no reduction in overhead, a standard file manager must

 *     work with multiple sequential compilations making the following

 *     example a recommended coding pattern:

 *

 *     <pre>

 *       File[] files1 = ... ; // input for first compilation task

 *       File[] files2 = ... ; // input for second compilation task

 *

 *       JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();

 *       StandardJavaFileManager fileManager = compiler.getStandardFileManager(null, null, null);

 *

 *       {@code Iterable<? extends JavaFileObject>} compilationUnits1 =

 *           fileManager.getJavaFileObjectsFromFiles({@linkplain java.util.Arrays#asList Arrays.asList}(files1));

 *       compiler.getTask(null, fileManager, null, null, null, compilationUnits1).call();

 *

 *       {@code Iterable<? extends JavaFileObject>} compilationUnits2 =

 *           fileManager.getJavaFileObjects(files2); // use alternative method

 *       // reuse the same file manager to allow caching of jar files

 *       compiler.getTask(null, fileManager, null, null, null, compilationUnits2).call();

 *

 *       fileManager.close();</pre>

 *

 *   </dd>

 *

 *   <dt>{@link DiagnosticCollector}</dt>

 *   <dd>

 *     Used to collect diagnostics in a list, for example:

 *     <pre>

 *       {@code Iterable<? extends JavaFileObject>} compilationUnits = ...;

 *       JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();

 *       {@code DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<JavaFileObject>();}

 *       StandardJavaFileManager fileManager = compiler.getStandardFileManager(diagnostics, null, null);

 *       compiler.getTask(null, fileManager, diagnostics, null, null, compilationUnits).call();

 *

 *       for ({@code Diagnostic<? extends JavaFileObject>} diagnostic : diagnostics.getDiagnostics())

 *           System.out.format("Error on line %d in %s%n",

 *                             diagnostic.getLineNumber(),

 *                             diagnostic.getSource().toUri());

 *

 *       fileManager.close();</pre>

 *   </dd>

 *

 *   <dt>

 *     {@link ForwardingJavaFileManager}, {@link ForwardingFileObject}, and

 *     {@link ForwardingJavaFileObject}

 *   </dt>

 *   <dd>

 *

 *     Subclassing is not available for overriding the behavior of a

 *     standard file manager as it is created by calling a method on a

 *     compiler, not by invoking a constructor.  Instead forwarding

 *     (or delegation) should be used.  These classes makes it easy to

 *     forward most calls to a given file manager or file object while

 *     allowing customizing behavior.  For example, consider how to

 *     log all calls to {@linkplain JavaFileManager#flush}:

 *

 *     <pre>

 *       final  Logger logger = ...;

 *       {@code Iterable<? extends JavaFileObject>} compilationUnits = ...;

 *       JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();

 *       StandardJavaFileManager stdFileManager = compiler.getStandardFileManager(null, null, null);

 *       JavaFileManager fileManager = new ForwardingJavaFileManager(stdFileManager) {

 *           public void flush() throws IOException {

 *               logger.entering(StandardJavaFileManager.class.getName(), "flush");

 *               super.flush();

 *               logger.exiting(StandardJavaFileManager.class.getName(), "flush");

 *           }

 *       };

 *       compiler.getTask(null, fileManager, null, null, null, compilationUnits).call();</pre>

 *   </dd>

 *

 *   <dt>{@link SimpleJavaFileObject}</dt>

 *   <dd>

 *

 *     This class provides a basic file object implementation which

 *     can be used as building block for creating file objects.  For

 *     example, here is how to define a file object which represent

 *     source code stored in a string:

 *

 *     <pre>

 *       /**

 *        * A file object used to represent source coming from a string.

 *        {@code *}/

 *       public class JavaSourceFromString extends SimpleJavaFileObject {

 *           /**

 *            * The source code of this "file".

 *            {@code *}/

 *           final String code;

 *

 *           /**

 *            * Constructs a new JavaSourceFromString.

 *            * {@code @}param name the name of the compilation unit represented by this file object

 *            * {@code @}param code the source code for the compilation unit represented by this file object

 *            {@code *}/

 *           JavaSourceFromString(String name, String code) {

 *               super({@linkplain java.net.URI#create URI.create}("string:///" + name.replace('.','/') + Kind.SOURCE.extension),

 *                     Kind.SOURCE);

 *               this.code = code;

 *           }

 *

 *           {@code @}Override

 *           public CharSequence getCharContent(boolean ignoreEncodingErrors) {

 *               return code;

 *           }

 *       }</pre>

 *   </dd>

 * </dl>

 *

 * @author Peter von der Ahé

 * @author Jonathan Gibbons

 * @see DiagnosticListener

 * @see Diagnostic

 * @see JavaFileManager

 * @since 1.6

 */

public interface JavaCompiler extends Tool, OptionChecker {

    /**

     * Creates a future for a compilation task with the given

     * components and arguments.  The compilation might not have

     * completed as described in the CompilationTask interface.

     *

     * <p>If a file manager is provided, it must be able to handle all

     * locations defined in {@link StandardLocation}.

     *

     * <p>Note that annotation processing can process both the

     * compilation units of source code to be compiled, passed with

     * the {@code compilationUnits} parameter, as well as class

     * files, whose names are passed with the {@code classes}

     * parameter.

     *

     * @param out a Writer for additional output from the compiler;

     * use {@code System.err} if {@code null}

     * @param fileManager a file manager; if {@code null} use the

     * compiler's standard filemanager

     * @param diagnosticListener a diagnostic listener; if {@code

     * null} use the compiler's default method for reporting

     * diagnostics

     * @param options compiler options, {@code null} means no options

     * @param classes names of classes to be processed by annotation

     * processing, {@code null} means no class names

     * @param compilationUnits the compilation units to compile, {@code

     * null} means no compilation units

     * @return an object representing the compilation

     * @throws RuntimeException if an unrecoverable error

     * occurred in a user supplied component.  The

     * {@linkplain Throwable#getCause() cause} will be the error in

     * user code.

     * @throws IllegalArgumentException if any of the options are invalid,

     * or if any of the given compilation units are of other kind than

     * {@linkplain JavaFileObject.Kind#SOURCE source}

     */

    CompilationTask getTask(Writer out,

                            JavaFileManager fileManager,

                            DiagnosticListener<? super JavaFileObject> diagnosticListener,

                            Iterable<String> options,

                            Iterable<String> classes,

                            Iterable<? extends JavaFileObject> compilationUnits);

    /**

     * Returns a new instance of the standard file manager implementation

     * for this tool.  The file manager will use the given diagnostic

     * listener for producing any non-fatal diagnostics.  Fatal errors

     * will be signaled with the appropriate exceptions.

     *

     * <p>The standard file manager will be automatically reopened if

     * it is accessed after calls to {@code flush} or {@code close}.

     * The standard file manager must be usable with other tools.

     *

     * @param diagnosticListener a diagnostic listener for non-fatal

     * diagnostics; if {@code null} use the compiler's default method

     * for reporting diagnostics

     * @param locale the locale to apply when formatting diagnostics;

     * {@code null} means the {@linkplain Locale#getDefault() default locale}.

     * @param charset the character set used for decoding bytes; if

     * {@code null} use the platform default

     * @return the standard file manager

     */

    StandardJavaFileManager getStandardFileManager(

        DiagnosticListener<? super JavaFileObject> diagnosticListener,

        Locale locale,

        Charset charset);

    /**

     * Interface representing a future for a compilation task.  The

     * compilation task has not yet started.  To start the task, call

     * the {@linkplain #call call} method.

     *

     * <p>Before calling the call method, additional aspects of the

     * task can be configured, for example, by calling the

     * {@linkplain #setProcessors setProcessors} method.

     */

    interface CompilationTask extends Callable<Boolean> {

        /**

         * Sets processors (for annotation processing).  This will

         * bypass the normal discovery mechanism.

         *

         * @param processors processors (for annotation processing)

         * @throws IllegalStateException if the task has started

         */

        void setProcessors(Iterable<? extends Processor> processors);

        /**

         * other localized data.

         *

         * @param locale the locale to apply; {@code null} means apply no

         * locale

         * @throws IllegalStateException if the task has started

         */

        void setLocale(Locale locale);

        /**

         * Performs this compilation task.  The compilation may only

         * be performed once.  Subsequent calls to this method throw

         * IllegalStateException.

         *

         * @return true if and only all the files compiled without errors;

         * false otherwise

         *

         * @throws RuntimeException if an unrecoverable error occurred

         * in a user-supplied component.  The

         * {@linkplain Throwable#getCause() cause} will be the error

         * in user code.

         * @throws IllegalStateException if called more than once

         */

        Boolean call();

    }

}