interp.java

rule engine drools-2.0-beta-18

package org.drools.semantics.groovy;

/*
 * $Id: Interp.java,v 1.13 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
 * 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.
 *
 */

import groovy.lang.Binding;
import groovy.lang.GroovyClassLoader;
import groovy.lang.GroovyCodeSource;
import groovy.lang.Script;
import org.drools.WorkingMemory;
import org.drools.rule.Declaration;
import org.drools.rule.Rule;
import org.drools.spi.ImportEntry;
import org.drools.spi.KnowledgeHelper;
import org.drools.spi.Tuple;

import java.io.IOException;
import java.io.Serializable;
import java.util.Iterator;
import java.util.Map;

/**
 * Base class for Groovy based semantic components.
 *
 * @see Eval
 * @see Exec
 *
 * @author <a href="mailto:[e-mail]">James Strachan </a>
 * @author <a href="mailto:[e-mail]">Christiaan ten Klooster </a>
 *
 * @version $Id: Interp.java,v 1.13 2004/11/29 12:35:52 simon Exp $
 */
public class Interp implements Serializable
{
    private static final String LINE_SEPARATOR = System.getProperty( "line.separator" );

    // ------------------------------------------------------------
    //     Instance members
    // ------------------------------------------------------------

    /** Text. */
    private final String text;

    /** The rule. */
    private final Rule rule;

    private transient Script code;

    // ------------------------------------------------------------
    //     Constructors
    // ------------------------------------------------------------

    /**
     * Construct.
     */
    protected Interp( String text, Rule rule )
    {
        this.rule = rule;
        this.text = text;
        try
        {
            StringBuffer newText = new StringBuffer( );
            Iterator it = rule.getImports( ).iterator();
            while (it.hasNext())
            {
                ImportEntry importEntry = (ImportEntry) it.next();
                if (importEntry instanceof GroovyImportEntry)
                {
                    newText.append("import ");
                    newText.append(importEntry.getImportEntry());
                    newText.append(";");
                    newText.append(LINE_SEPARATOR);
                }
            }
            newText.append(text);
            this.code = buildScript( newText.toString() );
        }
        catch ( Exception e )
        {
            e.printStackTrace( );
        }
    }

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

    /**
     * Retrieve the text to evaluate.
     *
     * @return The text to evaluate.
     */
    public String getText()
    {
        return this.text;
    }

    protected Script getCode()
    {
        return this.code;
    }

    protected Rule getRule()
    {
        return this.rule;
    }

    /**
     * Configure a <code>ScriptContext</code> using a <code>Tuple</code> for
     * variable bindings.
     *
     * @param tuple Tuple containing variable bindings.
     *
     * @return The dictionary
     */
    protected Binding setUpDictionary(Tuple tuple)
    {
        Binding dict = new Binding( );
        Declaration eachDecl;
        Iterator declIter = this.rule.getParameterDeclarations( ).iterator( );
        while ( declIter.hasNext( ) )
        {
            eachDecl = ( Declaration ) declIter.next( );

            dict.setVariable( eachDecl.getIdentifier( ).intern( ), tuple.get( eachDecl ) );
        }

        WorkingMemory workingMemory = tuple.getWorkingMemory( );

        dict.setVariable( "drools".intern( ), new KnowledgeHelper( this.rule, tuple ) );

        Map appDataMap = workingMemory.getApplicationDataMap( );

        for ( Iterator keyIter = appDataMap.keySet( ).iterator( ); keyIter.hasNext(); )
        {
            String key = ( String ) keyIter.next( );
            Object value = appDataMap.get( key );

            dict.setVariable( key, value );
        }

        return dict;
    }

    private Script buildScript(String text) throws Exception
    {
        GroovyCodeSource codeSource = new GroovyCodeSource( text,
                                                            "groovy.script",
                                                            "groovy.script" );
        GroovyClassLoader loader = new GroovyClassLoader(
                                                          Thread
                                                                .currentThread( )
                                                                .getContextClassLoader( ) );
        Class clazz = loader.parseClass( codeSource );

        return ( Script ) clazz.newInstance( );
    }

    /**
     * Extra work for serialization...
     */
    private void writeObject(java.io.ObjectOutputStream out) throws IOException
    {
        this.code = null;
        out.defaultWriteObject( );
    }

    /**
     * Extra work for serialization. re-creates the script object that is not
     * serialized
     */
    private void readObject(java.io.ObjectInputStream in) throws IOException,
                                                         ClassNotFoundException
    {
        in.defaultReadObject( );
        try
        {
            this.code = buildScript( this.getText( ) );
        }
        catch ( Exception e )
        {
            throw new IOException( "Error re-serializing Code Object. Error:"
                                   + e.getMessage( ) );
        }
    }
}