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Groovy example source code file (GroovyScriptEngineImpl.java)

This example Groovy source code file (GroovyScriptEngineImpl.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Groovy tags/keywords

class, class, closure, groovyclassloader, io, missingmethodexception, object, object, override, reflection, scriptcontext, scriptexception, scriptexception, string, string, t, util

The Groovy GroovyScriptEngineImpl.java source code

/*
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.  
 * Use is subject to license terms.
 *
 * Redistribution and use in source and binary forms, with or without modification, are 
 * permitted provided that the following conditions are met: Redistributions of source code 
 * must retain the above copyright notice, this list of conditions and the following disclaimer.
 * Redistributions in binary form must reproduce the above copyright notice, this list of 
 * conditions and the following disclaimer in the documentation and/or other materials 
 * provided with the distribution. Neither the name of the Sun Microsystems nor the names of 
 * is contributors may be used to endorse or promote products derived from this software 
 * without specific prior written permission. 

 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY 
 * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER 
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON 
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
package org.codehaus.groovy.jsr223;

import groovy.lang.Binding;
import groovy.lang.Closure;
import groovy.lang.DelegatingMetaClass;
import groovy.lang.GroovyClassLoader;
import groovy.lang.MetaClass;
import groovy.lang.MissingMethodException;
import groovy.lang.MissingPropertyException;
import groovy.lang.Script;
import groovy.lang.Tuple;

import org.codehaus.groovy.control.CompilationFailedException;
import org.codehaus.groovy.control.CompilerConfiguration;
import org.codehaus.groovy.syntax.SyntaxException;
import org.codehaus.groovy.runtime.InvokerHelper;
import org.codehaus.groovy.runtime.MetaClassHelper;
import org.codehaus.groovy.runtime.MethodClosure;

import javax.script.AbstractScriptEngine;
import javax.script.Bindings;
import javax.script.Compilable;
import javax.script.CompiledScript;
import javax.script.Invocable;
import javax.script.ScriptContext;
import javax.script.ScriptEngineFactory;
import javax.script.ScriptException;
import javax.script.SimpleBindings;

import java.io.IOException;
import java.io.PrintWriter;
import java.io.Reader;
import java.io.Writer;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

/*
 * @author Mike Grogan
 * @author A. Sundararajan
 * @author Jim White
 * @author Guillaume Laforge
 */
public class GroovyScriptEngineImpl
        extends AbstractScriptEngine implements Compilable, Invocable {

    private static boolean debug = false;

    // script-string-to-generated Class map
    private Map<String, Class> classMap;
    // global closures map - this is used to simulate a single
    // global functions namespace 
    private Map<String, Closure> globalClosures;
    // class loader for Groovy generated classes
    private GroovyClassLoader loader;
    // lazily initialized factory
    private volatile GroovyScriptEngineFactory factory;

    // counter used to generate unique global Script class names
    private static int counter;

    static {
        counter = 0;
    }

    public GroovyScriptEngineImpl() {
        classMap = Collections.synchronizedMap(new HashMap<String, Class>());
        globalClosures = Collections.synchronizedMap(new HashMap<String, Closure>());
        loader = new GroovyClassLoader(getParentLoader(),
                new CompilerConfiguration());
    }

    public Object eval(Reader reader, ScriptContext ctx)
            throws ScriptException {
        return eval(readFully(reader), ctx);
    }

    public Object eval(String script, ScriptContext ctx)
            throws ScriptException {
        try {
            Class clazz = getScriptClass(script);
            if (clazz == null) throw new ScriptException("Script class is null");
            return eval(clazz, ctx);
        } catch (SyntaxException e) {
            throw new ScriptException(e.getMessage(),
                    e.getSourceLocator(), e.getLine());
        } catch (Exception e) {
            if (debug) e.printStackTrace();
            throw new ScriptException(e);
        }
    }

    public Bindings createBindings() {
        return new SimpleBindings();
    }

    public ScriptEngineFactory getFactory() {
        if (factory == null) {
            synchronized (this) {
                if (factory == null) {
                    factory = new GroovyScriptEngineFactory();
                }
            }
        }
        return factory;
    }

    // javax.script.Compilable methods 
    public CompiledScript compile(String scriptSource) throws ScriptException {
        try {
            return new GroovyCompiledScript(this,
                    getScriptClass(scriptSource));
        } catch (SyntaxException e) {
            throw new ScriptException(e.getMessage(),
                    e.getSourceLocator(), e.getLine());
        } catch (IOException e) {
            throw new ScriptException(e);
        } catch (CompilationFailedException ee) {
            throw new ScriptException(ee);
        }
    }

    public CompiledScript compile(Reader reader) throws ScriptException {
        return compile(readFully(reader));
    }

    // javax.script.Invokable methods.
    public Object invokeFunction(String name, Object... args)
            throws ScriptException, NoSuchMethodException {
        return invokeImpl(null, name, args);
    }

    public Object invokeMethod(Object thiz, String name, Object... args)
            throws ScriptException, NoSuchMethodException {
        if (thiz == null) {
            throw new IllegalArgumentException("script object is null");
        }
        return invokeImpl(thiz, name, args);
    }

    public <T> T getInterface(Class clazz) {
        return makeInterface(null, clazz);
    }

    public <T> T getInterface(Object thiz, Class clazz) {
        if (thiz == null) {
            throw new IllegalArgumentException("script object is null");
        }
        return makeInterface(thiz, clazz);
    }

    // package-privates
    Object eval(Class scriptClass, final ScriptContext ctx) throws ScriptException {
        // Bindings so script has access to this environment.
        // Only initialize once.
        if (null == ctx.getAttribute("context", ScriptContext.ENGINE_SCOPE)) {
            // add context to bindings
            ctx.setAttribute("context", ctx, ScriptContext.ENGINE_SCOPE);

            // direct output to ctx.getWriter
            // If we're wrapping with a PrintWriter here,
            // enable autoFlush because otherwise it might not get done!
            final Writer writer = ctx.getWriter();
            ctx.setAttribute("out", (writer instanceof PrintWriter) ?
                    writer :
                    new PrintWriter(writer, true),
                    ScriptContext.ENGINE_SCOPE);

// Not going to do this after all (at least for now).
// Scripts can use context.{reader, writer, errorWriter}.
// That is a modern version of System.{in, out, err} or Console.{reader, writer}().
//
//            // New I/O names consistent with ScriptContext and java.io.Console.
//
//            ctx.setAttribute("writer", writer, ScriptContext.ENGINE_SCOPE);
//
//            // Direct errors to ctx.getErrorWriter
//            final Writer errorWriter = ctx.getErrorWriter();
//            ctx.setAttribute("errorWriter", (errorWriter instanceof PrintWriter) ?
//                                    errorWriter :
//                                    new PrintWriter(errorWriter),
//                                    ScriptContext.ENGINE_SCOPE);
//
//            // Get input from ctx.getReader
//            // We don't wrap with BufferedReader here because we expect that if
//            // the host wants that they do it.  Either way Groovy scripts will
//            // always have readLine because the GDK supplies it for Reader.
//            ctx.setAttribute("reader", ctx.getReader(), ScriptContext.ENGINE_SCOPE);
        }

        // Fix for GROOVY-3669: Can't use several times the same JSR-223 ScriptContext for differents groovy script
        if (ctx.getWriter() != null) {
            ctx.setAttribute("out", new PrintWriter(ctx.getWriter(), true), ScriptContext.ENGINE_SCOPE);
        }

        /*
         * We use the following Binding instance so that global variable lookup
         * will be done in the current ScriptContext instance.
         */
        Binding binding = new Binding(ctx.getBindings(ScriptContext.ENGINE_SCOPE)) {
            @Override
            public Object getVariable(String name) {
                synchronized (ctx) {
                    int scope = ctx.getAttributesScope(name);
                    if (scope != -1) {
                        return ctx.getAttribute(name, scope);
                    }
                }
                throw new MissingPropertyException(name, getClass());
            }

            @Override
            public void setVariable(String name, Object value) {
                synchronized (ctx) {
                    int scope = ctx.getAttributesScope(name);
                    if (scope == -1) {
                        scope = ScriptContext.ENGINE_SCOPE;
                    }
                    ctx.setAttribute(name, value, scope);
                }
            }
        };

        try {
            // if this class is not an instance of Script, it's a full-blown class
            // then simply return that class
            if (!Script.class.isAssignableFrom(scriptClass)) {
                return scriptClass;
            } else {
                // it's a script
                Script scriptObject = (Script) scriptClass.newInstance();
                scriptObject.setBinding(binding);

                // create a Map of MethodClosures from this new script object
                Method[] methods = scriptClass.getMethods();
                Map<String, Closure> closures = new HashMap();
                for (Method m : methods) {
                    String name = m.getName();
                    closures.put(name, new MethodClosure(scriptObject, name));
                }

                // save all current closures into global closures map
                globalClosures.putAll(closures);

                MetaClass oldMetaClass = scriptObject.getMetaClass();

                /*
                * We override the MetaClass of this script object so that we can
                * forward calls to global closures (of previous or future "eval" calls)
                * This gives the illusion of working on the same "global" scope.
                */
                scriptObject.setMetaClass(new DelegatingMetaClass(oldMetaClass) {
                    @Override
                    public Object invokeMethod(Object object, String name, Object args) {
                        if (args == null) {
                            return invokeMethod(object, name, MetaClassHelper.EMPTY_ARRAY);
                        }
                        if (args instanceof Tuple) {
                            return invokeMethod(object, name, ((Tuple) args).toArray());
                        }
                        if (args instanceof Object[]) {
                            return invokeMethod(object, name, (Object[]) args);
                        } else {
                            return invokeMethod(object, name, new Object[]{args});
                        }
                    }

                    @Override
                    public Object invokeMethod(Object object, String name, Object[] args) {
                        try {
                            return super.invokeMethod(object, name, args);
                        } catch (MissingMethodException mme) {
                            return callGlobal(name, args, ctx);
                        }
                    }

                    @Override
                    public Object invokeStaticMethod(Object object, String name, Object[] args) {
                        try {
                            return super.invokeStaticMethod(object, name, args);
                        } catch (MissingMethodException mme) {
                            return callGlobal(name, args, ctx);
                        }
                    }
                });

                return scriptObject.run();
            }
        } catch (Exception e) {
            throw new ScriptException(e);
        } finally {
            // Fix for GROOVY-3669: Can't use several times the same JSR-223 ScriptContext for different groovy script
            // Groovy's scripting engine implementation adds those two variables in the binding
            // but should clean up afterwards
            ctx.removeAttribute("context", ScriptContext.ENGINE_SCOPE);
            ctx.removeAttribute("out", ScriptContext.ENGINE_SCOPE);
        }
    }

    Class getScriptClass(String script)
            throws SyntaxException,
            CompilationFailedException,
            IOException {
        Class clazz = classMap.get(script);
        if (clazz != null) {
            return clazz;
        }

        clazz = loader.parseClass(script, generateScriptName());
        classMap.put(script, clazz);
        return clazz;
    }

    public void setClassLoader(final GroovyClassLoader classLoader) {
        this.loader = classLoader;
    }

    public GroovyClassLoader getClassLoader() {
        return this.loader;
    }

    //-- Internals only below this point

    // invokes the specified method/function on the given object.
    private Object invokeImpl(Object thiz, String name, Object... args)
            throws ScriptException, NoSuchMethodException {
        if (name == null) {
            throw new NullPointerException("method name is null");
        }

        try {
            if (thiz != null) {
                return InvokerHelper.invokeMethod(thiz, name, args);
            } else {
                return callGlobal(name, args);
            }
        } catch (MissingMethodException mme) {
            throw new NoSuchMethodException(mme.getMessage());
        } catch (Exception e) {
            throw new ScriptException(e);
        }
    }

    // call the script global function of the given name
    private Object callGlobal(String name, Object[] args) {
        return callGlobal(name, args, context);
    }

    private Object callGlobal(String name, Object[] args, ScriptContext ctx) {
        Closure closure = globalClosures.get(name);
        if (closure != null) {
            return closure.call(args);
        } else {
            // Look for closure valued variable in the 
            // given ScriptContext. If available, call it.
            Object value = ctx.getAttribute(name);
            if (value instanceof Closure) {
                return ((Closure) value).call(args);
            } // else fall thru..
        }
        throw new MissingMethodException(name, getClass(), args);
    }

    // generate a unique name for top-level Script classes
    private synchronized String generateScriptName() {
        return "Script" + (++counter) + ".groovy";
    }

    private <T> T makeInterface(Object obj, Class clazz) {
        final Object thiz = obj;
        if (clazz == null || !clazz.isInterface()) {
            throw new IllegalArgumentException("interface Class expected");
        }
        return (T) Proxy.newProxyInstance(
                clazz.getClassLoader(),
                new Class[]{clazz},
                new InvocationHandler() {
                    public Object invoke(Object proxy, Method m, Object[] args)
                            throws Throwable {
                        return invokeImpl(thiz, m.getName(), args);
                    }
                });
    }

    // determine appropriate class loader to serve as parent loader
    // for GroovyClassLoader instance
    private ClassLoader getParentLoader() {
        // check whether thread context loader can "see" Groovy Script class
        ClassLoader ctxtLoader = Thread.currentThread().getContextClassLoader();
        try {
            Class c = ctxtLoader.loadClass(Script.class.getName());
            if (c == Script.class) {
                return ctxtLoader;
            }
        } catch (ClassNotFoundException cnfe) {
            /* ignore */
        }
        // exception was thrown or we get wrong class
        return Script.class.getClassLoader();
    }

    private String readFully(Reader reader) throws ScriptException {
        char[] arr = new char[8 * 1024]; // 8K at a time
        StringBuilder buf = new StringBuilder();
        int numChars;
        try {
            while ((numChars = reader.read(arr, 0, arr.length)) > 0) {
                buf.append(arr, 0, numChars);
            }
        } catch (IOException exp) {
            throw new ScriptException(exp);
        }
        return buf.toString();
    }
} 

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