# ScriptMediator.java

    /*
     * Copyright (c) 2017, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
     *
     * WSO2 Inc. licenses this file to you under the Apache License,
     * Version 2.0 (the "License"); you may not use this file except
     * in compliance with the License.
     * You may obtain a copy of the License at
     *
     * http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing,
     * software distributed under the License is distributed on an
     * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
     * KIND, either express or implied. See the License for the
     * specific language governing permissions and limitations
     * under the License.
     */

    package org.apache.synapse.mediators.bsf;

    import com.google.gson.JsonParser;
    import com.oracle.truffle.js.scriptengine.GraalJSEngineFactory;
    import com.sun.phobos.script.javascript.RhinoScriptEngineFactory;
    import com.sun.script.groovy.GroovyScriptEngineFactory;
    import com.sun.script.jruby.JRubyScriptEngineFactory;
    import com.sun.script.jython.JythonScriptEngineFactory;
    import org.apache.axiom.om.OMElement;
    import org.apache.axiom.om.OMText;
    import org.apache.bsf.xml.XMLHelper;
    import org.apache.commons.logging.Log;
    import org.apache.commons.logging.LogFactory;
    import org.apache.synapse.MessageContext;
    import org.apache.synapse.SynapseException;
    import org.apache.synapse.SynapseLog;
    import org.apache.synapse.commons.json.JsonUtil;
    import org.apache.synapse.commons.util.MiscellaneousUtil;
    import org.apache.synapse.config.Entry;
    import org.apache.synapse.core.axis2.Axis2MessageContext;
    import org.apache.synapse.mediators.AbstractMediator;
    import org.apache.synapse.mediators.Value;
    import org.apache.synapse.mediators.bsf.access.control.AccessControlUtils;
    import org.apache.synapse.mediators.bsf.access.control.SandboxContextFactory;
    import org.apache.synapse.mediators.bsf.access.control.config.AccessControlConfig;
    import org.apache.synapse.mediators.bsf.access.control.config.AccessControlListType;
    import org.apache.synapse.mediators.eip.EIPUtils;
    import org.graalvm.polyglot.Context;
    import org.mozilla.javascript.ClassShutter;
    import org.mozilla.javascript.ContextFactory;

    import javax.activation.DataHandler;
    import javax.script.*;
    import java.io.BufferedReader;
    import java.io.IOException;
    import java.io.InputStreamReader;
    import java.util.Arrays;
    import java.util.Comparator;
    import java.util.List;
    import java.util.Map;
    import java.util.Properties;
    import java.util.TreeMap;
    import java.util.concurrent.BlockingQueue;
    import java.util.concurrent.LinkedBlockingQueue;

    import static org.apache.synapse.mediators.bsf.ScriptMediatorConstants.JAVA_SCRIPT;
    import static org.apache.synapse.mediators.bsf.ScriptMediatorConstants.MC_VAR_NAME;
    import static org.apache.synapse.mediators.bsf.ScriptMediatorConstants.NASHORN;
    import static org.apache.synapse.mediators.bsf.ScriptMediatorConstants.NASHORN_JAVA_SCRIPT;
    import static org.apache.synapse.mediators.bsf.ScriptMediatorConstants.ORACLE_NASHORN_NAME;
    import static org.apache.synapse.mediators.bsf.ScriptMediatorConstants.POOL_SIZE_PROPERTY;
    import static org.apache.synapse.mediators.bsf.ScriptMediatorConstants.RHINO_JAVA_SCRIPT;
    import static org.apache.synapse.mediators.bsf.access.control.AccessControlConstants.CLASS_PREFIXES;
    import static org.apache.synapse.mediators.bsf.access.control.AccessControlConstants.ENABLE;
    import static org.apache.synapse.mediators.bsf.access.control.AccessControlConstants.LIMIT_CLASS_ACCESS_PREFIX;
    import static org.apache.synapse.mediators.bsf.access.control.AccessControlConstants.LIMIT_NATIVE_OBJECT_ACCESS_PREFIX;
    import static org.apache.synapse.mediators.bsf.access.control.AccessControlConstants.LIST_TYPE;
    import static org.apache.synapse.mediators.bsf.access.control.AccessControlConstants.OBJECT_NAMES;

    /**
     * A Synapse mediator that calls a function in any scripting language supported by the BSF.
     * The ScriptMediator supports scripts specified in-line or those loaded through a registry
     * <p/>
     * <pre>
     *    &lt;script [key=&quot;entry-key&quot;]
     *      [function=&quot;script-function-name&quot;] language="nashornJs|javascript|groovy|ruby"&gt
     *      (text | xml)?
     *    &lt;/script&gt;
     * </pre>
     * <p/>
     * <p/>
     * The function is an optional attribute defining the name of the script function to call,
     * if not specified it defaults to a function named 'mediate'. The function takes a single
     * parameter which is the Synapse MessageContext. The function may return a boolean, if it
     * does not then true is assumed.
     */
    public class ScriptMediator extends AbstractMediator {

        private static final Log logger = LogFactory.getLog(ScriptMediator.class.getName());

        /**
         * The registry entry key for a script loaded from the registry
         * Handle both static and dynamic(Xpath) Keys
         */
        private Value key;
        /**
         * The language of the script code
         */
        private String language;
        /**
         * The map of included scripts; key = registry entry key, value = script source
         */
        private final Map<Value, Object> includes;
        /**
         * The optional name of the function to be invoked, defaults to mediate
         */
        private String function = "mediate";
        /**
         * The source code of the script
         */
        private String scriptSourceCode;
        /**
         * The BSF engine created to process each message through the script
         */
        protected ScriptEngine scriptEngine;
        /**
         * The BSF engine created to validate each JSON payload
         */
        protected ScriptEngine jsEngine;
        /**
         * Does the ScriptEngine support multi-threading
         */
        private boolean multiThreadedEngine;
        /**
         * The compiled script. Only used for inline scripts
         */
        private CompiledScript compiledScript;
        /**
         * The BSF helper to convert between the XML representations used by Java
         * and the scripting language
         */
        private XMLHelper xmlHelper;
        /**
         * Script Engine Manger
         */
        private ScriptEngineManager engineManager;
        /**
         * Default Pool Size
         */
        private int DEFAULT_POOL_SIZE = 15;
        /**
         * Pool size
         */
        private int poolSize = DEFAULT_POOL_SIZE;
        /**
         * Pool ScriptEngine Resources
         */
        private BlockingQueue<ScriptEngineWrapper> pool;
        /**
         * JSON parser used to parse JSON strings
         */
        private JsonParser jsonParser;

        /**
         * Store the class loader from properties
         */
        private ClassLoader loader;

        /**
         * Store the Oracle Nashorn Factory if available in the JDK
         */
        private ScriptEngineFactory oracleNashornFactory;

        /**
         * Store java class access control config
         */
        private AccessControlConfig classAccessControlConfig;

        /**
         * Store java method access config
         */
        private AccessControlConfig nativeObjectAccessControlConfig;

        /**
         * Create a script mediator for the given language and given script source.
         *
         * @param language         the BSF language
         * @param scriptSourceCode the source code of the script
         */
        public ScriptMediator(String language, String scriptSourceCode, ClassLoader classLoader) {
            this.language = language;
            this.scriptSourceCode = scriptSourceCode;
            this.setLoader(classLoader);
            this.includes = new TreeMap<Value, Object>();
            initInlineScript();
        }

        /**
         * Create a script mediator for the given language and given script entry key and function.
         *
         * @param language       the BSF language
         * @param includeKeysMap Include script keys
         * @param key            the registry entry key to load the script
         * @param function       the function to be invoked
         */
        public ScriptMediator(String language, Map<Value, Object> includeKeysMap,
                              Value key, String function, ClassLoader classLoader) {
            this.language = language;
            this.key = key;
            this.setLoader(classLoader);
            this.includes = includeKeysMap;
            if (function != null) {
                this.function = function;
            }

            Properties properties = MiscellaneousUtil.loadProperties("synapse.properties");
            poolSize = Integer.parseInt(properties.getProperty(POOL_SIZE_PROPERTY, String.valueOf(DEFAULT_POOL_SIZE)));

            initScriptEngine();
            if (!(scriptEngine instanceof Invocable)) {
                throw new SynapseException("Script engine is not an Invocable" +
                        " engine for language: " + language);
            }

        }

        /**
         * Perform Script mediation.
         *
         * @param synCtx the Synapse message context
         * @return the boolean result from the script invocation
         */
        public boolean mediate(MessageContext synCtx) {

            if (synCtx.getEnvironment().isDebuggerEnabled()) {
                if (super.divertMediationRoute(synCtx)) {
                    return true;
                }
            }

            SynapseLog synLog = getLog(synCtx);

            if (synLog.isTraceOrDebugEnabled()) {
                synLog.traceOrDebug("Start : Script mediator");

                if (synLog.isTraceTraceEnabled()) {
                    synLog.traceTrace("Message : " + synCtx.getEnvelope());
                }
            }

            if (synLog.isTraceOrDebugEnabled()) {
                synLog.traceOrDebug("Scripting language : " + language + " source " +
                        (key == null ? ": specified inline " : " loaded with key : " + key) +
                        (function != null ? " function : " + function : ""));
            }

            boolean returnValue;
            if (multiThreadedEngine) {
                returnValue = invokeScript(synCtx);
            } else {
                // TODO: change to use a pool of script engines (requires an update to BSF)
                synchronized (scriptEngine.getClass()) {
                    returnValue = invokeScript(synCtx);
                }
            }

            if (synLog.isTraceTraceEnabled()) {
                synLog.traceTrace("Result message after execution of script : " + synCtx.getEnvelope());
            }

            if (synLog.isTraceOrDebugEnabled()) {
                synLog.traceOrDebug("End : Script mediator return value : " + returnValue);
            }
            return returnValue;
        }

        private boolean invokeScript(MessageContext synCtx) {
            boolean returnValue;
            Context context = null;
            try {
                //if the engine is Rhino then needs to set the class loader specifically
                if (language.equals(RHINO_JAVA_SCRIPT)) {
                    org.mozilla.javascript.Context cx = org.mozilla.javascript.Context.enter();
                    if (classAccessControlConfig != null && classAccessControlConfig.isAccessControlEnabled()) {
                        cx.setClassShutter(createClassShutter());
                    }
                    cx.setApplicationClassLoader(this.loader);
                }
                if (language.equals(JAVA_SCRIPT)) {
                    context = Context.newBuilder("js").allowExperimentalOptions(true).build();
                    context.enter();
                }

                Object returnObject;
                if (key != null) {
                    returnObject = mediateWithExternalScript(synCtx, context);
                } else {
                    returnObject = mediateForInlineScript(synCtx, context);
                }
                returnValue = !(returnObject != null && returnObject instanceof Boolean) || (Boolean) returnObject;

            } catch (ScriptException e) {
                handleException("The script engine returned an error executing the " +
                        (key == null ? "inlined " : "external ") + language + " script" +
                        (key != null ? " : " + key : "") +
                        (function != null ? " function " + function : ""), e, synCtx);
                returnValue = false;
            } catch (NoSuchMethodException e) {
                handleException("The script engine returned a NoSuchMethodException executing the " +
                        "external " + language + " script" + " : " + key +
                        (function != null ? " function " + function : ""), e, synCtx);
                returnValue = false;
            } catch (Exception e) {
                handleException("The script engine returned an Exception executing the " +
                        "external " + language + " script" + " : " + key +
                        (function != null ? " function " + function : ""), e, synCtx);
                returnValue = false;
            } finally {
                if (language.equals(RHINO_JAVA_SCRIPT)) {
                    org.mozilla.javascript.Context.exit();
                }
                if (language.equals("js")) {
                    if (context != null) {
                        context.leave();
                    }
                }
            }

            return returnValue;
        }

        /**
         * Mediation implementation when the script to be executed should be loaded from the registry
         *
         * @param synCtx the message context
         * @param context the context of script engine
         * @return script result
         * @throws ScriptException       For any errors , when compile, run the script
         * @throws NoSuchMethodException If the function is not defined in the script
         */
        private Object mediateWithExternalScript(MessageContext synCtx, Context context)
                throws ScriptException, NoSuchMethodException {
            ScriptEngineWrapper sew = null;
            Object obj;
            try {
                sew = prepareExternalScript(synCtx);
                XMLHelper helper;
                if (language.equalsIgnoreCase(JAVA_SCRIPT) || language.equals(NASHORN_JAVA_SCRIPT) ||
                        language.equals(RHINO_JAVA_SCRIPT)) {
                    helper = xmlHelper;
                } else {
                    helper = XMLHelper.getArgHelper(sew.getEngine());
                }
                ScriptMessageContext scriptMC;
                scriptMC = getScriptMessageContext(synCtx, helper, context);
                processJSONPayload(synCtx, scriptMC);
                Invocable invocableScript = (Invocable) sew.getEngine();

                obj = invocableScript.invokeFunction(function, new Object[]{scriptMC});
            } finally {
              if(sew != null){
                  // return engine to front of queue or drop if queue is full (i.e. if getNewScriptEngine() spawns a new engine)
                  pool.offer(sew);
              }
            }

            return obj;
        }

        /**
         * Get script message context according to scripting language.
         *
         * @param synCtx message context
         * @param helper Object which help to convert xml into OMelemnt
         * @return Nashorn or Common script message context according to language attribute
         */
        private ScriptMessageContext getScriptMessageContext(MessageContext synCtx, XMLHelper helper,
                                                             Context context) {
            ScriptMessageContext scriptMC;
            if (language.equals(NASHORN_JAVA_SCRIPT)) {
                // nashorn is deprecated and will be removed in the future in favor of graal.js
                try {
                    if(isJDKContainNashorn()) {
                        scriptMC = new NashornJavaScriptMessageContext(synCtx, helper, jsEngine);
                    } else {
                        scriptMC = new OpenJDKNashornJavaScriptMessageContext(synCtx, helper, jsEngine);
                    }
                } catch (ScriptException e) {
                    throw new SynapseException("Error occurred while evaluating empty json object", e);
                }

            } else if (language.equals(JAVA_SCRIPT)) {
                try {
                    scriptMC = new GraalVMJavaScriptMessageContext(synCtx, helper, context);
                } catch (ScriptException e) {
                    throw new SynapseException("Error occurred while evaluating empty json object", e);
                }
            } else {
                scriptMC = new CommonScriptMessageContext(synCtx, helper);
            }
            return scriptMC;
        }

        /**
         * Perform mediation with static inline script of the given scripting language
         *
         * @param synCtx message context
         * @return true, or the script return value
         * @throws ScriptException For any errors , when compile , run the script
         */
        private Object mediateForInlineScript(MessageContext synCtx, Context context) throws ScriptException {
            ScriptMessageContext scriptMC;
            scriptMC = getScriptMessageContext(synCtx, xmlHelper, context);
            processJSONPayload(synCtx, scriptMC);
            Bindings bindings = scriptEngine.createBindings();
            bindings.put(MC_VAR_NAME, scriptMC);

            Object response;
            if (compiledScript != null) {
                response = compiledScript.eval(bindings);
            } else {
                response = scriptEngine.eval(scriptSourceCode, bindings);
            }
            return response;
        }

        private void processJSONPayload(MessageContext synCtx, ScriptMessageContext scriptMC) throws ScriptException {
            if (!(synCtx instanceof Axis2MessageContext)) {
                return;
            }
            org.apache.axis2.context.MessageContext messageContext = ((Axis2MessageContext) synCtx).getAxis2MessageContext();
            String jsonString = (String) messageContext.getProperty("JSON_STRING");
            Object jsonObject = null;
            prepareForJSON(scriptMC);
            if (JsonUtil.hasAJsonPayload(messageContext)) {
                try {
                    String jsonPayload = JsonUtil.jsonPayloadToString(messageContext);
                    if (NASHORN_JAVA_SCRIPT.equals(language)) {
                        if(isJDKContainNashorn()) {
                            jsonObject = ((NashornJavaScriptMessageContext) scriptMC).jsonSerializerCallMember("parse", jsonPayload);
                        } else {
                            jsonObject = ((OpenJDKNashornJavaScriptMessageContext) scriptMC).jsonSerializerCallMember("parse", jsonPayload);
                        }
                    } else if (JAVA_SCRIPT.equals(language)) {
                        jsonObject = ((GraalVMJavaScriptMessageContext) scriptMC).jsonSerializerCallMember("parse", jsonPayload);
                    } else {
                        String scriptWithJsonParser = "JSON.parse(JSON.stringify(" + jsonPayload + "))";
                        jsonObject = this.jsEngine.eval('(' + scriptWithJsonParser + ')');
                    }
                } catch (ScriptException e) {
                    throw new ScriptException("Invalid JSON payload", e.getFileName(), e.getLineNumber(),
                            e.getColumnNumber());
                }
            } else if (jsonString != null) {
                String jsonPayload = EIPUtils.tryParseJsonString(jsonParser, jsonString).toString();
                jsonObject = this.jsEngine.eval('(' + jsonPayload + ')');
            }
            if (jsonObject != null) {
                scriptMC.setJsonObject(synCtx, jsonObject);
            }
        }

        private void prepareForJSON(ScriptMessageContext scriptMC) {
            if (jsonParser == null) {
                jsonParser = new JsonParser();
            }
            scriptMC.setScriptEngine(this.jsEngine);
        }

        /**
         * Initialise the Mediator for the inline script
         */
        protected void initInlineScript() {
            try {
                initScriptEngine();

                if (scriptEngine instanceof Compilable) {
                    if (log.isDebugEnabled()) {
                        log.debug("Script engine supports Compilable interface, " +
                                "compiling script code..");
                    }
                    compiledScript = ((Compilable) scriptEngine).compile(scriptSourceCode);
                } else {
                    // do nothing. If the script engine doesn't support Compilable then
                    // the inline script will be evaluated on each invocation
                    if (log.isDebugEnabled()) {
                        log.debug("Script engine does not support the Compilable interface, " +
                                "in-lined script would be evaluated on each invocation..");
                    }
                }

            } catch (ScriptException e) {
                throw new SynapseException("Exception initializing inline script", e);
            }
        }

        /**
         * Prepares the mediator for the invocation of an external script
         *
         * @param synCtx MessageContext script
         * @throws ScriptException For any errors , when compile the script
         */
        protected ScriptEngineWrapper prepareExternalScript(MessageContext synCtx)
                throws ScriptException {

            // Derive actual key from xpath expression or get static key
            String generatedScriptKey = key.evaluateValue(synCtx);
            Entry entry = synCtx.getConfiguration().getEntryDefinition(generatedScriptKey);
            boolean needsReload = (entry != null) && entry.isDynamic() &&
                    (!entry.isCached() || entry.isExpired());

            ScriptEngineWrapper sew = getNewScriptEngine();
            Bindings engineBinding = sew.getEngine().getBindings(ScriptContext.ENGINE_SCOPE);
            engineBinding.clear(); // if we don't do this, previous state can affect successive executions! ESBJAVA-4583

            if (scriptSourceCode == null || needsReload || !sew.isInitialized()) {
                Object o = synCtx.getEntry(generatedScriptKey);
                if (o instanceof OMElement) {
                    scriptSourceCode = ((OMElement) (o)).getText();
                    sew.getEngine().eval(scriptSourceCode, engineBinding);
                } else if (o instanceof String) {
                    scriptSourceCode = (String) o;
                    sew.getEngine().eval(scriptSourceCode, engineBinding);
                } else if (o instanceof OMText) {
                    DataHandler dataHandler = (DataHandler) ((OMText) o).getDataHandler();
                    if (dataHandler != null) {
                        BufferedReader reader = null;
                        try {
                            reader = new BufferedReader(
                                    new InputStreamReader(dataHandler.getInputStream()));
                            StringBuilder scriptSB = new StringBuilder();
                            String currentLine;
                            while ((currentLine = reader.readLine()) != null) {
                                scriptSB.append(currentLine).append('\n');
                            }
                            scriptSourceCode = scriptSB.toString();
                            sew.getEngine().eval(scriptSourceCode, engineBinding);
                        } catch (IOException e) {
                            handleException("Error in reading script as a stream ", e, synCtx);
                        } finally {

                            if (reader != null) {
                                try {
                                    reader.close();
                                } catch (IOException e) {
                                    handleException("Error in closing input stream ", e, synCtx);
                                }
                            }

                        }
                    }
                }

            } else {
                sew.getEngine().eval(scriptSourceCode, engineBinding); // Will drop TPS, but is required for ESBJAVA-4583
            }

            // load <include /> scripts; reload each script if needed
            for (Value includeKey : includes.keySet()) {

                String includeSourceCode = (String) includes.get(includeKey);

                String generatedKey = includeKey.evaluateValue(synCtx);

                Entry includeEntry = synCtx.getConfiguration().getEntryDefinition(generatedKey);
                boolean includeEntryNeedsReload = (includeEntry != null) && includeEntry.isDynamic()
                        && (!includeEntry.isCached() || includeEntry.isExpired());
                if (includeSourceCode == null || includeEntryNeedsReload || !sew.isInitialized()) {
                    log.debug("Re-/Loading the include script with key " + includeKey);
                    Object o = synCtx.getEntry(generatedKey);
                    if (o instanceof OMElement) {
                        includeSourceCode = ((OMElement) (o)).getText();
                        sew.getEngine().eval(includeSourceCode, engineBinding);
                    } else if (o instanceof String) {
                        includeSourceCode = (String) o;
                        sew.getEngine().eval(includeSourceCode, engineBinding);
                    } else if (o instanceof OMText) {
                        DataHandler dataHandler = (DataHandler) ((OMText) o).getDataHandler();
                        if (dataHandler != null) {
                            BufferedReader reader = null;
                            try {
                                reader = new BufferedReader(
                                        new InputStreamReader(dataHandler.getInputStream()));
                                StringBuilder scriptSB = new StringBuilder();
                                String currentLine;
                                while ((currentLine = reader.readLine()) != null) {
                                    scriptSB.append(currentLine).append('\n');
                                }
                                includeSourceCode = scriptSB.toString();
                                sew.getEngine().eval(includeSourceCode, engineBinding);
                            } catch (IOException e) {
                                handleException("Error in reading script as a stream ", e, synCtx);
                            } finally {

                                if (reader != null) {
                                    try {
                                        reader.close();
                                    } catch (IOException e) {
                                        handleException("Error in closing input" +
                                                " stream ", e, synCtx);
                                    }
                                }
                            }
                        }
                    }
                    includes.put(includeKey, includeSourceCode);
                } else {
                    sew.getEngine().eval(includeSourceCode, engineBinding); // Will drop TPS, but required for ESBJAVA-4583
                }
            }

            sew.setInitialized(true);

            return sew;
        }

        protected void initScriptEngine() {
            if (log.isDebugEnabled()) {
                log.debug("Initializing script mediator for language : " + language);
            }
            System.setProperty("polyglot.engine.WarnInterpreterOnly", "false");
            System.setProperty("polyglot.js.nashorn-compat", "true");
            engineManager = new ScriptEngineManager();
            if (language.equals(JAVA_SCRIPT)) {
                engineManager.registerEngineExtension("jsEngine", new GraalJSEngineFactory());
            }
            if (language.equals(RHINO_JAVA_SCRIPT)) {
                engineManager.registerEngineExtension("jsEngine", new RhinoScriptEngineFactory());
            }
            engineManager.registerEngineExtension("groovy", new GroovyScriptEngineFactory());
            engineManager.registerEngineExtension("rb", new JRubyScriptEngineFactory());
            engineManager.registerEngineExtension("py", new JythonScriptEngineFactory());
            oracleNashornFactory = getOracleNashornFactory();
            if (language.equals(NASHORN_JAVA_SCRIPT)) {
                if (isJDKContainNashorn()) {
                    engineManager.registerEngineName(NASHORN, oracleNashornFactory);
                } else {
                    engineManager.registerEngineName(NASHORN, OpenJDKNashornFactoryWrapper.getOpenJDKNashornFactory());
                }
            }
            if (language.equals(NASHORN_JAVA_SCRIPT)) {
                this.scriptEngine = engineManager.getEngineByName(NASHORN);
            } else if (language.equals(RHINO_JAVA_SCRIPT)) {
                this.scriptEngine = engineManager.getEngineByExtension("jsEngine");
            } else {
                this.scriptEngine = engineManager.getEngineByExtension(language);
            }

            pool = new LinkedBlockingQueue<ScriptEngineWrapper>(poolSize);

            for (int i = 0; i< poolSize; i++) {
                ScriptEngineWrapper sew;
                if (language.equals(NASHORN_JAVA_SCRIPT)) {
                    sew = new ScriptEngineWrapper(engineManager.getEngineByName(NASHORN));
                } else if (language.equals(RHINO_JAVA_SCRIPT)) {
                    sew = new ScriptEngineWrapper(engineManager.getEngineByExtension("jsEngine"));
                } else {
                    sew = new ScriptEngineWrapper(engineManager.getEngineByExtension(language));
                }
                pool.add(sew);
            }
            if (language.equals(NASHORN_JAVA_SCRIPT)) {
                this.jsEngine = engineManager.getEngineByName(NASHORN);
            } else {
                this.jsEngine = engineManager.getEngineByExtension("jsEngine");
            }
            if (scriptEngine == null) {
                handleException("No script engine found for language: " + language);
            }
            if (language.equalsIgnoreCase(JAVA_SCRIPT) || language.equals(NASHORN_JAVA_SCRIPT)) {
                xmlHelper = new ExtendedJavaScriptXmlHelper();
            } else if (language.equals(RHINO_JAVA_SCRIPT)) {
                // this will be removed in the future in favor of graal.js
                xmlHelper = new JavaScriptXmlHelper();
            } else {
                xmlHelper = XMLHelper.getArgHelper(scriptEngine);
            }

            this.multiThreadedEngine = scriptEngine.getFactory().getParameter("THREADING") != null;
            if (language.equals(JAVA_SCRIPT)) {
                this.multiThreadedEngine = true;
            }
            log.debug("Script mediator for language : " + language +
                    " supports multithreading? : " + multiThreadedEngine);

            if (language.equals(RHINO_JAVA_SCRIPT)) {
                readAccessControlConfigurations(MiscellaneousUtil.loadProperties("synapse.properties"));
                if (nativeObjectAccessControlConfig != null && nativeObjectAccessControlConfig.isAccessControlEnabled() &&
                        !ContextFactory.hasExplicitGlobal()) {
                    ContextFactory.initGlobal(new SandboxContextFactory(nativeObjectAccessControlConfig));
                }
            }
        }

        public String getLanguage() {
            return language;
        }

        public Value getKey() {
            return key;
        }

        public String getFunction() {
            return function;
        }

        public String getScriptSrc() {
            return scriptSourceCode;
        }

        private void handleException(String msg) {
            log.error(msg);
            throw new SynapseException(msg);
        }

        public Map<Value, Object> getIncludeMap() {
            return includes;
        }

        public ClassLoader getLoader() {
            return loader;
        }

        public void setLoader(ClassLoader loader) {
            this.loader = loader;
        }

        public ScriptEngineWrapper getNewScriptEngine() {

            ScriptEngineWrapper scriptEngineWrapper = pool.poll();
            if (scriptEngineWrapper == null) {
                if (language.equals(NASHORN_JAVA_SCRIPT)) {
                    scriptEngineWrapper = new ScriptEngineWrapper(engineManager.getEngineByName(NASHORN));
                } else if (language.equals(RHINO_JAVA_SCRIPT)) {
                    scriptEngineWrapper = new ScriptEngineWrapper(engineManager.getEngineByExtension("jsEngine"));
                } else {
                    scriptEngineWrapper = new ScriptEngineWrapper(engineManager.getEngineByExtension(language));
                }
            }
            // fall back
            return scriptEngineWrapper;
        }

        public boolean isContentAltering() {
            return true;
        }

        private boolean isJDKContainNashorn() {
            return oracleNashornFactory != null;
        }

        private ScriptEngineFactory getOracleNashornFactory() {
            ScriptEngineManager engineManager = new ScriptEngineManager();
            List<ScriptEngineFactory> engineFactories = engineManager.getEngineFactories();
            for (ScriptEngineFactory engineFactory : engineFactories) {
                if (engineFactory.getEngineName().equals(ORACLE_NASHORN_NAME)) {
                    return engineFactory;
                }
            }
            if (engineManager.getEngineByName(NASHORN) != null) {
                return engineManager.getEngineByName(NASHORN).getFactory();
            }
            return null;
        }

        /**
         * @deprecated This method is deprecated and will be removed in a future release in favour of GraalVM JS engine.
         * Creates a class shutter, which will be used inside the context that executes the script.
         * This class shutter will be used to control the visibility of classes specified in the access control config,
         * to the script.
         * @return
         */
        @Deprecated
        private ClassShutter createClassShutter() {
            return new ClassShutter() {
                public boolean visibleToScripts(String className) {
                    /*
                    This will be used to compare whether the current fully qualified class name starts with
                    any of the provided set of strings provided in the access control config.
                    */
                    Comparator<String> startsWithComparator = new Comparator<String>() {
                        @Override
                        public int compare(String o1, String o2) {
                            if (o1 == null || o2 == null) {
                                return -1;
                            }
                            if (o1.startsWith(o2)) {
                                return 1;
                            }
                            return -1;
                        }
                    };
                    return AccessControlUtils.isAccessAllowed(className, classAccessControlConfig, startsWithComparator);
                }
            };
        }

        /**
         * Reads and sets access control configurations.
         * @param properties    Synapse properties.
         */
        private void readAccessControlConfigurations(Properties properties) {
            String limitClassAccessEnabled = properties.getProperty(LIMIT_CLASS_ACCESS_PREFIX + ENABLE);
            if (Boolean.parseBoolean(limitClassAccessEnabled)) {
                String limitClassAccessListType = properties.getProperty(LIMIT_CLASS_ACCESS_PREFIX + LIST_TYPE);
                String limitClassAccessClassPrefixes = properties.getProperty(LIMIT_CLASS_ACCESS_PREFIX + CLASS_PREFIXES);
                this.classAccessControlConfig = new AccessControlConfig(true,
                        AccessControlListType.valueOf(limitClassAccessListType),
                        Arrays.asList(limitClassAccessClassPrefixes.split(",")));
            }

            String limitNativeObjectAccessEnabled = properties.getProperty(LIMIT_NATIVE_OBJECT_ACCESS_PREFIX + ENABLE);
            if (Boolean.parseBoolean(limitNativeObjectAccessEnabled)) {
                String limitNativeObjectAccessListType =
                        properties.getProperty(LIMIT_NATIVE_OBJECT_ACCESS_PREFIX + LIST_TYPE);
                String limitNativeObjectAccessClassPrefixes =
                        properties.getProperty(LIMIT_NATIVE_OBJECT_ACCESS_PREFIX + OBJECT_NAMES);
                this.nativeObjectAccessControlConfig = new AccessControlConfig(true,
                        AccessControlListType.valueOf(limitNativeObjectAccessListType),
                        Arrays.asList(limitNativeObjectAccessClassPrefixes.split(",")));
            }
        }

    }