trunk/proposal/embed/src/java/org/apache/tools/ant/taskdefs/optional/JexlProperties.java

/*
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2000-2002 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. 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.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "The Jakarta Project", "Ant", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
 *    from this software without prior written permission. For written
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 * 5. Products derived from this software may not be called "Apache"
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 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * 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.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

package org.apache.tools.ant.taskdefs.optional;

import org.apache.tools.ant.*;
import org.apache.tools.ant.PropertyHelper;
import org.apache.tools.ant.types.*;
import java.io.*;
import java.util.*;

import org.apache.commons.jexl.*;

/**
 *  Enable JEXL dynamic properties
 *  
 *
 */
public class JexlProperties extends Task {
    public static String PREFIX="jexl:";
    JexlPropertyHelper helper=new JexlPropertyHelper();

    public JexlProperties() {
    }

    static class JexlPropertyHelper extends PropertyHelper {
        JexlContext jc;

        public Object getPropertyHook( String ns, String name, boolean user ) {
            if( ! name.startsWith(PREFIX) ) {
                return super.getPropertyHook(ns, name, user);
            }
            try {
                name=name.substring( PREFIX.length() );
                Expression e = ExpressionFactory.createExpression(name);
                Object o = e.evaluate(jc);

                return o;
            } catch( Exception ex ) {
                ex.printStackTrace();
                return null;
            }
        }
    }
    
    public void execute() {
        /*
         *  First make a jexlContext and put stuff in it
         */
        helper.jc = JexlHelper.createContext();
        helper.jc.getVars().put("ant", project);

        // register it
        PropertyHelper phelper=PropertyHelper.getPropertyHelper( project );
        helper.setNext( phelper.getNext() );
        helper.setProject( project );
        phelper.setNext( helper );



    }    
}