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 * Copyright (c) 2005, 2016, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package javax.script;

import java.util.List;

/**

 * <code>ScriptEngineFactory</code> is used to describe and instantiate

 * <code>ScriptEngines</code>.

 * <br><br>

 * Each class implementing <code>ScriptEngine</code> has a corresponding

 * factory that exposes metadata describing the engine class.

 * <br><br>The <code>ScriptEngineManager</code>

 * uses the service-provider loader mechanism described in the

 * {@link java.util.ServiceLoader} class to obtain

 * instances of {@code ScriptEngineFactory} instances.

 * See {@link ScriptEngineManager#ScriptEngineManager()} and

 * {@link ScriptEngineManager#ScriptEngineManager(java.lang.ClassLoader)}.

 *

 * @since 1.6

 */

public interface ScriptEngineFactory {

    /**

     * Returns the full  name of the <code>ScriptEngine</code>.  For

     * instance an implementation based on the Mozilla Rhino Javascript engine

     * might return <i>Rhino Mozilla Javascript Engine</i>.

     * @return The name of the engine implementation.

     */

    public String getEngineName();

    /**

     * Returns the version of the <code>ScriptEngine</code>.

     * @return The <code>ScriptEngine</code> implementation version.

     */

    public String getEngineVersion();

    /**

     * Returns an immutable list of filename extensions, which generally identify scripts

     * written in the language supported by this <code>ScriptEngine</code>.

     * The array is used by the <code>ScriptEngineManager</code> to implement its

     * <code>getEngineByExtension</code> method.

     * @return The list of extensions.

     */

    public List<String> getExtensions();

    /**

     * Returns an immutable list of mimetypes, associated with scripts that

     * can be executed by the engine.  The list is used by the

     * <code>ScriptEngineManager</code> class to implement its

     * <code>getEngineByMimetype</code> method.

     * @return The list of mime types.

     */

    public List<String> getMimeTypes();

    /**

     * Returns an immutable list of  short names for the <code>ScriptEngine</code>, which may be used to

     * identify the <code>ScriptEngine</code> by the <code>ScriptEngineManager</code>.

     * For instance, an implementation based on the Mozilla Rhino Javascript engine might

     * return list containing {"javascript", "rhino"}.

     * @return an immutable list of short names

     */

    public List<String> getNames();

    /**

     * Returns the name of the scripting language supported by this

     * <code>ScriptEngine</code>.

     * @return The name of the supported language.

     */

    public String getLanguageName();

    /**

     * Returns the version of the scripting language supported by this

     * <code>ScriptEngine</code>.

     * @return The version of the supported language.

     */

    public String getLanguageVersion();

    /**

     * Returns the value of an attribute whose meaning may be implementation-specific.

     * Keys for which the value is defined in all implementations are:

     * <ul>

     * <li>ScriptEngine.ENGINE</li>

     * <li>ScriptEngine.ENGINE_VERSION</li>

     * <li>ScriptEngine.LANGUAGE</li>

     * <li>ScriptEngine.LANGUAGE_VERSION</li>

     * <li>ScriptEngine.NAME</li>

     * </ul>

     * <p>

     * The values for these keys are the Strings returned by <code>getEngineName</code>,

     * <code>getEngineVersion</code>, <code>getLanguageName</code>,

     * <code>getLanguageVersion</code> for the first four keys respectively. For NAME, one of the Strings

     * returned by <code>getNames</code> is returned.<br><br>

     * A reserved key, <code><b>THREADING</b></code>, whose value describes the behavior of the engine

     * with respect to concurrent execution of scripts and maintenance of state is also defined.

     * These values for the <code><b>THREADING</b></code> key are:<br><br>

     * <ul>

     * <li><code>null</code> - The engine implementation is not thread safe, and cannot

     * be used to execute scripts concurrently on multiple threads.

     * <li><code>&quot;MULTITHREADED&quot;</code> - The engine implementation is internally

     * thread-safe and scripts may execute concurrently although effects of script execution

     * on one thread may be visible to scripts on other threads.

     * <li><code>&quot;THREAD-ISOLATED&quot;</code> - The implementation satisfies the requirements

     * of "MULTITHREADED", and also, the engine maintains independent values

     * for symbols in scripts executing on different threads.

     * <li><code>&quot;STATELESS&quot;</code> - The implementation satisfies the requirements of

     * <code>&quot;THREAD-ISOLATED&quot;</code>.  In addition, script executions do not alter the

     * mappings in the <code>Bindings</code> which is the engine scope of the

     * <code>ScriptEngine</code>.  In particular, the keys in the <code>Bindings</code>

     * and their associated values are the same before and after the execution of the script.

     * </ul>

     * <br><br>

     * Implementations may define implementation-specific keys.

     *

     * @param key The name of the parameter

     * @return The value for the given parameter. Returns <code>null</code> if no

     * value is assigned to the key.

     *

     * @throws NullPointerException if the key is null.

     */

    public Object getParameter(String key);

    /**

     * Returns a String which can be used to invoke a method of a  Java object using the syntax

     * of the supported scripting language.  For instance, an implementation for a Javascript

     * engine might be;

     *

     * <pre>{@code

     * public String getMethodCallSyntax(String obj,

     *                                   String m, String... args) {

     *      String ret = obj;

     *      ret += "." + m + "(";

     *      for (int i = 0; i < args.length; i++) {

     *          ret += args[i];

     *          if (i < args.length - 1) {

     *              ret += ",";

     *          }

     *      }

     *      ret += ")";

     *      return ret;

     * }

     * } </pre>

     *

     * @param obj The name representing the object whose method is to be invoked. The

     * name is the one used to create bindings using the <code>put</code> method of

     * <code>ScriptEngine</code>, the <code>put</code> method of an <code>ENGINE_SCOPE</code>

     * <code>Bindings</code>,or the <code>setAttribute</code> method

     * of <code>ScriptContext</code>.  The identifier used in scripts may be a decorated form of the

     * specified one.

     *

     * @param m The name of the method to invoke.

     * @param args names of the arguments in the method call.

     *

     * @return The String used to invoke the method in the syntax of the scripting language.

     *

     * @throws NullPointerException if obj or m or args or any of the elements of args is null.

     */

    public String getMethodCallSyntax(String obj, String m, String... args);

    /**

     * Returns a String that can be used as a statement to display the specified String  using

     * the syntax of the supported scripting language.  For instance, the implementation for a Perl

     * engine might be;

     *

     * <pre><code>

     * public String getOutputStatement(String toDisplay) {

     *      return "print(" + toDisplay + ")";

     * }

     * </code></pre>

     *

     * @param toDisplay The String to be displayed by the returned statement.

     * @return The string used to display the String in the syntax of the scripting language.

     *

     *

     */

    public String getOutputStatement(String toDisplay);

    /**

     * Returns a valid scripting language executable program with given statements.

     * For instance an implementation for a PHP engine might be:

     *

     * <pre>{@code

     * public String getProgram(String... statements) {

     *      String retval = "<?\n";

     *      int len = statements.length;

     *      for (int i = 0; i < len; i++) {

     *          retval += statements[i] + ";\n";

     *      }

     *      return retval += "?>";

     * }

     * }</pre>

     *

     *  @param statements The statements to be executed.  May be return values of

     *  calls to the <code>getMethodCallSyntax</code> and <code>getOutputStatement</code> methods.

     *  @return The Program

     *

     *  @throws NullPointerException if the <code>statements</code> array or any of its elements is null

     */

    public String getProgram(String... statements);

    /**

     * Returns an instance of the <code>ScriptEngine</code> associated with this

     * <code>ScriptEngineFactory</code>. A new ScriptEngine is generally

     * returned, but implementations may pool, share or reuse engines.

     *

     * @return A new <code>ScriptEngine</code> instance.

     */

    public  ScriptEngine getScriptEngine();

}