SubstringFunction.java

/**********************************************************************
Copyright (c) 2008 Andy Jefferson and others. All rights reserved.
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.

Contributors:
    ...
**********************************************************************/
package org.datanucleus.query.inmemory.method;

import org.datanucleus.exceptions.NucleusException;
import org.datanucleus.query.QueryUtils;
import org.datanucleus.query.expression.InvokeExpression;
import org.datanucleus.query.expression.Literal;
import org.datanucleus.query.expression.ParameterExpression;
import org.datanucleus.query.expression.PrimaryExpression;
import org.datanucleus.query.inmemory.InMemoryExpressionEvaluator;
import org.datanucleus.query.inmemory.InvocationEvaluator;

/**
 * Evaluator for the function SUBSTRING(str, num1, num2).
 */
public class SubstringFunction implements InvocationEvaluator
{
    /* (non-Javadoc)
     * @see org.datanucleus.query.evaluator.memory.InvocationEvaluator#evaluate(org.datanucleus.query.expression.InvokeExpression, org.datanucleus.query.evaluator.memory.InMemoryExpressionEvaluator)
     */
    public Object evaluate(InvokeExpression expr, Object invokedValue, InMemoryExpressionEvaluator eval)
    {
        String method = expr.getOperation();
        Object param = expr.getArguments().get(0);
        Object paramValue = null;
        if (param instanceof PrimaryExpression)
        {
            PrimaryExpression primExpr = (PrimaryExpression)param;
            paramValue = eval.getValueForPrimaryExpression(primExpr);
        }
        else if (param instanceof ParameterExpression)
        {
            ParameterExpression paramExpr = (ParameterExpression)param;
            paramValue = QueryUtils.getValueForParameterExpression(eval.getParameterValues(), paramExpr);
        }
        else if (param instanceof Literal)
        {
            paramValue = ((Literal)param).getLiteral();
        }
        else
        {
            throw new NucleusException(method + "(param, num1, num2) where param is instanceof " + param.getClass().getName() + " not supported");
        }
        if (paramValue == null)
        {
            return null;
        }

        Object num1 = expr.getArguments().get(1);
        int num1Value = -1;
        if (num1 instanceof Literal)
        {
            // Extract Integer from arithmetic Literal
            num1Value = eval.getIntegerForLiteral((Literal)num1);
        }
        else
        {
            throw new NucleusException(method + "(param, num1, num2) where num1 is instanceof " + num1.getClass().getName() + " not supported");
        }

        Object num2 = expr.getArguments().get(2);
        int num2Value = -1;
        if (num2 instanceof Literal)
        {
            num2Value = eval.getIntegerForLiteral((Literal)num2);
        }
        else
        {
            throw new NucleusException(method + "(param, num1, num2) where num2 is instanceof " + num2.getClass().getName() + " not supported");
        }

        return ((String)paramValue).substring(num1Value, num2Value);
    }
}