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/* * Copyright (c) 2005, 2006, 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.io.Reader;import java.util.Map;import java.util.Iterator; /** * Provides a standard implementation for several of the variants of the <code>eval</code> * method. * <br><br> * <code><b>eval(Reader)</b></code><p><code><b>eval(String)</b></code><p> * <code><b>eval(String, Bindings)</b></code><p><code><b>eval(Reader, Bindings)</b></code> * <br><br> are implemented using the abstract methods * <br><br> * <code><b>eval(Reader,ScriptContext)</b></code> or * <code><b>eval(String, ScriptContext)</b></code> * <br><br> * with a <code>SimpleScriptContext</code>. * <br><br> * A <code>SimpleScriptContext</code> is used as the default <code>ScriptContext</code> * of the <code>AbstractScriptEngine</code>.. * * @author Mike Grogan * @since 1.6 */public abstract class AbstractScriptEngine  implements ScriptEngine {     /**     * The default <code>ScriptContext</code> of this <code>AbstractScriptEngine</code>.     */     protected ScriptContext context;     /**     * Creates a new instance of AbstractScriptEngine using a <code>SimpleScriptContext</code>     * as its default <code>ScriptContext</code>.     */    public AbstractScriptEngine() {         context = new SimpleScriptContext();     }     /**     * Creates a new instance using the specified <code>Bindings</code> as the     * <code>ENGINE_SCOPE</code> <code>Bindings</code> in the protected <code>context</code> field.     *     * @param n The specified <code>Bindings</code>.     * @throws NullPointerException if n is null.     */    public AbstractScriptEngine(Bindings n) {         this();        if (n == null) {            throw new NullPointerException("n is null");        }        context.setBindings(n, ScriptContext.ENGINE_SCOPE);    }     /**     * Sets the value of the protected <code>context</code> field to the specified     * <code>ScriptContext</code>.     *     * @param ctxt The specified <code>ScriptContext</code>.     * @throws NullPointerException if ctxt is null.     */    public void setContext(ScriptContext ctxt) {        if (ctxt == null) {            throw new NullPointerException("null context");        }        context = ctxt;    }     /**     * Returns the value of the protected <code>context</code> field.     *     * @return The value of the protected <code>context</code> field.     */    public ScriptContext getContext() {        return context;    }     /**     * Returns the <code>Bindings</code> with the specified scope value in     * the protected <code>context</code> field.     *     * @param scope The specified scope     *     * @return The corresponding <code>Bindings</code>.     *     * @throws IllegalArgumentException if the value of scope is     * invalid for the type the protected <code>context</code> field.     */    public Bindings getBindings(int scope) {         if (scope == ScriptContext.GLOBAL_SCOPE) {            return context.getBindings(ScriptContext.GLOBAL_SCOPE);        } else if (scope == ScriptContext.ENGINE_SCOPE) {            return context.getBindings(ScriptContext.ENGINE_SCOPE);        } else {            throw new IllegalArgumentException("Invalid scope value.");        }    }     /**     * Sets the <code>Bindings</code> with the corresponding scope value in the     * <code>context</code> field.     *     * @param bindings The specified <code>Bindings</code>.     * @param scope The specified scope.     *     * @throws IllegalArgumentException if the value of scope is     * invalid for the type the <code>context</code> field.     * @throws NullPointerException if the bindings is null and the scope is     * <code>ScriptContext.ENGINE_SCOPE</code>     */    public void setBindings(Bindings bindings, int scope) {         if (scope == ScriptContext.GLOBAL_SCOPE) {            context.setBindings(bindings, ScriptContext.GLOBAL_SCOPE);;        } else if (scope == ScriptContext.ENGINE_SCOPE) {            context.setBindings(bindings, ScriptContext.ENGINE_SCOPE);;        } else {            throw new IllegalArgumentException("Invalid scope value.");        }    }     /**     * Sets the specified value with the specified key in the <code>ENGINE_SCOPE</code>     * <code>Bindings</code> of the protected <code>context</code> field.     *     * @param key The specified key.     * @param value The specified value.     *     * @throws NullPointerException if key is null.     * @throws IllegalArgumentException if key is empty.     */    public void put(String key, Object value) {         Bindings nn = getBindings(ScriptContext.ENGINE_SCOPE);        if (nn != null) {            nn.put(key, value);        }     }     /**     * Gets the value for the specified key in the <code>ENGINE_SCOPE</code> of the     * protected <code>context</code> field.     *     * @return The value for the specified key.     *     * @throws NullPointerException if key is null.     * @throws IllegalArgumentException if key is empty.     */    public Object get(String key) {         Bindings nn = getBindings(ScriptContext.ENGINE_SCOPE);        if (nn != null) {            return nn.get(key);        }         return null;    }      /**     * <code>eval(Reader, Bindings)</code> calls the abstract     * <code>eval(Reader, ScriptContext)</code> method, passing it a <code>ScriptContext</code>     * whose Reader, Writers and Bindings for scopes other that <code>ENGINE_SCOPE</code>     * are identical to those members of the protected <code>context</code> field.  The specified     * <code>Bindings</code> is used instead of the <code>ENGINE_SCOPE</code>     *     * <code>Bindings</code> of the <code>context</code> field.     *     * @param reader A <code>Reader</code> containing the source of the script.     * @param bindings A <code>Bindings</code> to use for the <code>ENGINE_SCOPE</code>     * while the script executes.     *     * @return The return value from <code>eval(Reader, ScriptContext)</code>     * @throws ScriptException if an error occurs in script.     * @throws NullPointerException if any of the parameters is null.     */    public Object eval(Reader reader, Bindings bindings ) throws ScriptException {         ScriptContext ctxt = getScriptContext(bindings);         return eval(reader, ctxt);    }      /**     * Same as <code>eval(Reader, Bindings)</code> except that the abstract     * <code>eval(String, ScriptContext)</code> is used.     *     * @param script A <code>String</code> containing the source of the script.     *     * @param bindings A <code>Bindings</code> to use as the <code>ENGINE_SCOPE</code>     * while the script executes.     *     * @return The return value from <code>eval(String, ScriptContext)</code>     * @throws ScriptException if an error occurs in script.     * @throws NullPointerException if any of the parameters is null.     */    public Object eval(String script, Bindings bindings) throws ScriptException {         ScriptContext ctxt = getScriptContext(bindings);         return eval(script , ctxt);    }     /**     * <code>eval(Reader)</code> calls the abstract     * <code>eval(Reader, ScriptContext)</code> passing the value of the <code>context</code>     * field.     *     * @param reader A <code>Reader</code> containing the source of the script.     * @return The return value from <code>eval(Reader, ScriptContext)</code>     * @throws ScriptException if an error occurs in script.     * @throws NullPointerException if any of the parameters is null.     */    public Object eval(Reader reader) throws ScriptException {          return eval(reader, context);    }     /**     * Same as <code>eval(Reader)</code> except that the abstract     * <code>eval(String, ScriptContext)</code> is used.     *     * @param script A <code>String</code> containing the source of the script.     * @return The return value from <code>eval(String, ScriptContext)</code>     * @throws ScriptException if an error occurrs in script.     * @throws NullPointerException if any of the parameters is null.     */    public Object eval(String script) throws ScriptException {          return eval(script, context);    }     /**     * Returns a <code>SimpleScriptContext</code>.  The <code>SimpleScriptContext</code>:     *<br><br>     * <ul>     * <li>Uses the specified <code>Bindings</code> for its <code>ENGINE_SCOPE</code>     * </li>     * <li>Uses the <code>Bindings</code> returned by the abstract <code>getGlobalScope</code>     * method as its <code>GLOBAL_SCOPE</code>     * </li>     * <li>Uses the Reader and Writer in the default <code>ScriptContext</code> of this     * <code>ScriptEngine</code>     * </li>     * </ul>     * <br><br>     * A <code>SimpleScriptContext</code> returned by this method is used to implement eval methods     * using the abstract <code>eval(Reader,Bindings)</code> and <code>eval(String,Bindings)</code>     * versions.     *     * @param nn Bindings to use for the <code>ENGINE_SCOPE</code>     * @return The <code>SimpleScriptContext</code>     */    protected ScriptContext getScriptContext(Bindings nn) {         SimpleScriptContext ctxt = new SimpleScriptContext();        Bindings gs = getBindings(ScriptContext.GLOBAL_SCOPE);         if (gs != null) {            ctxt.setBindings(gs, ScriptContext.GLOBAL_SCOPE);        }         if (nn != null) {            ctxt.setBindings(nn,                    ScriptContext.ENGINE_SCOPE);        } else {            throw new NullPointerException("Engine scope Bindings may not be null.");        }         ctxt.setReader(context.getReader());        ctxt.setWriter(context.getWriter());        ctxt.setErrorWriter(context.getErrorWriter());         return ctxt;     }}