ExprNumberSetFrequency.java

/*
 * *************************************************************************************
 *  Copyright (C) 2008 EsperTech, Inc. All rights reserved.                            *
 *  http://esper.codehaus.org                                                          *
 *  http://www.espertech.com                                                           *
 *  ---------------------------------------------------------------------------------- *
 *  The software in this package is published under the terms of the GPL license       *
 *  a copy of which has been included with this distribution in the license.txt file.  *
 * *************************************************************************************
 */

package com.espertech.esper.epl.expression;

import com.espertech.esper.client.EventBean;
import com.espertech.esper.util.JavaClassHelper;
import com.espertech.esper.type.FrequencyParameter;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.util.Map;

/**
 * Expression for use within crontab to specify a frequency.
 */
public class ExprNumberSetFrequency extends ExprNodeBase implements ExprEvaluator
{
    private static final Log log = LogFactory.getLog(ExprNumberSetFrequency.class);
    private transient ExprEvaluator evaluator;
    private static final long serialVersionUID = -5389069399403078192L;

    @Override
    public ExprEvaluator getExprEvaluator() {
        return this;
    }

    public String toExpressionString()
    {
        return "*/" + this.getChildNodes().get(0);
    }

    public boolean isConstantResult()
    {
        return this.getChildNodes().get(0).isConstantResult();
    }

    public boolean equalsNode(ExprNode node)
    {
        if (!(node instanceof ExprNumberSetFrequency))
        {
            return false;
        }
        return true;
    }

    public void validate(ExprValidationContext validationContext) throws ExprValidationException
    {
        evaluator = this.getChildNodes().get(0).getExprEvaluator();
        Class type = evaluator.getType();
        if (!(JavaClassHelper.isNumericNonFP(type)))
        {
            throw new ExprValidationException("Frequency operator requires an integer-type parameter");
        }
    }

    public Class getType()
    {
        return FrequencyParameter.class;
    }

    public Map<String, Object> getEventType() {
        return null;
    }

    public Object evaluate(EventBean[] eventsPerStream, boolean isNewData, ExprEvaluatorContext exprEvaluatorContext)
    {
        Object value = evaluator.evaluate(eventsPerStream, isNewData, exprEvaluatorContext);
        if (value == null)
        {
            log.warn("Null value returned for frequency parameter");
            return new FrequencyParameter(Integer.MAX_VALUE);
        }
        else
        {
            int intValue = ((Number) value).intValue();
            return new FrequencyParameter(intValue);
        }
    }
}