ifthenfunction.java

开源的axion的数据库代码

/*
/* $Id: IfThenFunction.java,v 1.2 2003/07/07 20:22:16 rwald Exp $ tag
 * =======================================================================
 * Copyright (c) 2002 Axion Development Team.  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 names "Tigris", "Axion", nor the names of its contributors may
 *    not be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 *
 * 4. Products derived from this software may not be called "Axion", nor
 *    may "Tigris" or "Axion" appear in their names 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.axiondb.functions;

import org.axiondb.AxionException;
import org.axiondb.DataType;
import org.axiondb.FunctionFactory;
import org.axiondb.RowDecorator;
import org.axiondb.Selectable;
import org.axiondb.WhereNode;
import org.axiondb.types.AnyType;

/**
 * <code>IFTHEN(<i>condition</i> <i>value</i>)</code>:
 * returns value if condition evalates to true; else,
 * it returns null. 
 *
 * @version $Revision: 1.2 $ $Date: 2003/07/07 20:22:16 $
 * @author Amrish Lal
 */
public class IfThenFunction extends BaseFunction implements ScalarFunction, FunctionFactory {
    public IfThenFunction() {
        super("IFTHEN");
    }

    public ConcreteFunction makeNewInstance() {
        return new IfThenFunction();
    }
    
    /** {@link AnyType} */
    public DataType getDataType() {
        return _returnType;
    }

    public Object evaluate(RowDecorator row) throws AxionException {
        WhereNode where = null;
        try {
            where = (WhereNode) getArgument(0);
        } catch(ClassCastException e) {
            throw new AxionException("Expected WhereNode",e);
        }
        Selectable sel = getArgument(1);
        Object result = null;
        if (((Boolean)where.evaluate(row)).booleanValue()) {
            result = sel.evaluate(row);
            _returnType = sel.getDataType();
        }
        return (result);
    }

    public boolean isValid() {
        return (getArgumentCount() == 2);
    }

    private DataType _returnType = new AnyType();
}