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Groovy example source code file (GroovyEngine.java)

This example Groovy source code file (GroovyEngine.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

bsfexception, bsfexception, closure, closure, exception, groovy, groovyengine, groovyshell, object, object, string, string, stringbuffer, util, vector

The Groovy GroovyEngine.java source code

/*
 * Copyright 2003-2007 the original author or authors.
 *
 * Licensed 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.codehaus.groovy.bsf;

import groovy.lang.Closure;
import groovy.lang.GroovyShell;
import org.apache.bsf.BSFDeclaredBean;
import org.apache.bsf.BSFException;
import org.apache.bsf.BSFManager;
import org.apache.bsf.util.BSFEngineImpl;
import org.apache.bsf.util.BSFFunctions;
import org.codehaus.groovy.runtime.InvokerHelper;

import java.util.Vector;

/**
 * A BSF Engine for the <a href="http://groovy.codehaus.org/">Groovy
 * scripting language.
 * <p/>
 * It's derived from the Jython / JPython engine
 *
 * @author James Strachan
 */
public class GroovyEngine extends BSFEngineImpl {
    protected GroovyShell shell;

    /*
     * Convert a non java class name to a java classname
     * This is used to convert a script name to a name
     * that can be used as a classname with the script is
     * loaded in GroovyClassloader#load()
     * The method simply replaces any invalid characters
     * with "_".
     */
    private String convertToValidJavaClassname(String inName) {
        if (inName == null || inName.equals("")) {
            return "_";
        }
        StringBuffer output = new StringBuffer(inName.length());
        boolean firstChar = true;
        for (int i = 0; i < inName.length(); ++i) {
            char ch = inName.charAt(i);
            if (firstChar && !Character.isJavaIdentifierStart(ch)) {
                ch = '_';
            } else if (!firstChar
                    && !(Character.isJavaIdentifierPart(ch) || ch == '.')) {
                ch = '_';
            }
            firstChar = (ch == '.');
            output.append(ch);
        }
        return output.toString();
    }

    /**
     * Allow an anonymous function to be declared and invoked
     */
    public Object apply(String source, int lineNo, int columnNo, Object funcBody, Vector paramNames,
                        Vector arguments) throws BSFException {
        Object object = eval(source, lineNo, columnNo, funcBody);
        if (object instanceof Closure) {
            // lets call the function
            Closure closure = (Closure) object;
            return closure.call(arguments.toArray());
        }
        return object;
    }

    /**
     * Call the named method of the given object.
     */
    public Object call(Object object, String method, Object[] args) throws BSFException {
        return InvokerHelper.invokeMethod(object, method, args);
    }

    /**
     * Evaluate an expression.
     */
    public Object eval(String source, int lineNo, int columnNo, Object script) throws BSFException {
        try {
            source = convertToValidJavaClassname(source);
            return getEvalShell().evaluate(script.toString(), source);
        } catch (Exception e) {
            throw new BSFException(BSFException.REASON_EXECUTION_ERROR, "exception from Groovy: " + e, e);
        }
    }

    /**
     * Execute a script.
     */
    public void exec(String source, int lineNo, int columnNo, Object script) throws BSFException {
        try {
            // use evaluate to pass in the BSF variables
            source = convertToValidJavaClassname(source);
            getEvalShell().evaluate(script.toString(), source);
        } catch (Exception e) {
            throw new BSFException(BSFException.REASON_EXECUTION_ERROR, "exception from Groovy: " + e, e);
        }
    }

    /**
     * Initialize the engine.
     */
    public void initialize(BSFManager mgr, String lang, Vector declaredBeans) throws BSFException {
        super.initialize(mgr, lang, declaredBeans);

        // create a shell
        shell = new GroovyShell(mgr.getClassLoader());

        // register the mgr with object name "bsf"
        shell.setVariable("bsf", new BSFFunctions(mgr, this));

        int size = declaredBeans.size();
        for (int i = 0; i < size; i++) {
            declareBean((BSFDeclaredBean) declaredBeans.elementAt(i));
        }
    }

    /**
     * Declare a bean
     */
    public void declareBean(BSFDeclaredBean bean) throws BSFException {
        shell.setVariable(bean.name, bean.bean);
    }

    /**
     * Undeclare a previously declared bean.
     */
    public void undeclareBean(BSFDeclaredBean bean) throws BSFException {
        shell.setVariable(bean.name, null);
    }

    /**
     * @return a newly created GroovyShell using the same variable scope but a new class loader
     */
    protected GroovyShell getEvalShell() {
        return new GroovyShell(shell);
    }
}

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