Java tutorial
/* * Copyright (c) 2005, 2013, 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 occurs 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(context.getReader(), context.getWriter(), context.getErrorWriter()); 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."); } return ctxt; } }