Java tutorial
/* * 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 * or visit www.oracle.com if you need additional information or have any * questions. */ 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>"MULTITHREADED"</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>"THREAD-ISOLATED"</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>"STATELESS"</code> - The implementation satisfies the requirements of * <code>"THREAD-ISOLATED"</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(); }