eval.java

rule engine drools-2.0-beta-18

package org.drools.semantics.python;

/*
 * $Id: Eval.java,v 1.17 2004/11/29 12:35:52 simon Exp $
 *
 * Copyright 2002 (C) The Werken Company. All Rights Reserved.
 *
 * Redistribution and use of this software and associated documentation
 * ("Software"), with or without modification, are permitted provided that the
 * following conditions are met:
 *
 * 1. Redistributions of source code must retain copyright statements and
 * notices. Redistributions must also contain a copy of this document.
 *
 * 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 name "drools" must not be used to endorse or promote products derived
 * from this Software without prior written permission of The Werken Company.
 * For written permission, please contact [e-mail].
 *
 * 4. Products derived from this Software may not be called "drools" nor may
 * "drools" appear in their names without prior written permission of The Werken
 * Company. "drools" is a registered trademark of The Werken Company.
 *
 * 5. Due credit should be given to The Werken Company.
 * (http://drools.werken.com/).
 *
 * THIS SOFTWARE IS PROVIDED BY THE WERKEN COMPANY AND CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESSED 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 WERKEN COMPANY OR ITS 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
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 */

import org.drools.rule.Declaration;
import org.drools.rule.Rule;
import org.drools.spi.Tuple;
import org.python.core.PyDictionary;
import org.python.core.PyObject;
import org.python.core.__builtin__;

/**
 * Base class for Jython expression-based Python semantic components.
 *
 * @see ExprCondition
 *s
 * @author <a href="mailto:[e-mail]">bob mcwhirter </a>
 * @author <a href="mailto:[e-mail]">Christiaan ten Klooster </a>
 */
public class Eval extends Interp
{
    // ------------------------------------------------------------
    //     Instance members
    // ------------------------------------------------------------

    /** Required decls. */
    private Declaration[] decls;

    //  private PyFunction evalFunc;
    // ------------------------------------------------------------
    //     Constructors
    // ------------------------------------------------------------

    /**
     * Construct.
     */
    protected Eval(String text, Rule rule ) throws Exception
    {
        super( text, rule, "eval" );

        ExprAnalyzer analyzer = new ExprAnalyzer( );

        this.decls = analyzer.analyze( getNode( ),
                                       rule.getParameterDeclarations( ) );
    }

    // ------------------------------------------------------------
    //     Instance methods
    // ------------------------------------------------------------

    /**
     * Evaluate.
     *
     * @param tuple Tuple containing variable bindings.
     *
     * @return The result of evaluation.
     */
    public Object evaluate(Tuple tuple) throws Exception
    {
        PyDictionary dict = setUpDictionary( tuple );

        return evaluate( dict );
    }

    /**
     * Evaluate.
     *
     * @param locals The evaluation dictionary.
     *
     * @return The result of evaluation.
     */
    protected Object evaluate(PyDictionary locals) throws Exception
    {

        PyObject result = __builtin__.eval( getCode( ),
                                            locals,
                                            getGlobals( ) );

        return result.__tojava__( Object.class );
    }

    /**
     * Retrieve the array of <code>Declaration</code> s required by this
     * condition to perform its duties.
     *
     * @return The array of <code>Declarations</code> expected on incoming
     *         <code>Tuples</code>.
     */
    public Declaration[] getRequiredTupleMembers()
    {
        return this.decls;
    }
}