GroupByViewFactory.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.view.std;

import com.espertech.esper.client.EventType;
import com.espertech.esper.client.annotation.Hint;
import com.espertech.esper.client.annotation.HintEnum;
import com.espertech.esper.core.context.util.AgentInstanceViewFactoryChainContext;
import com.espertech.esper.core.service.StatementContext;
import com.espertech.esper.epl.expression.ExprNode;
import com.espertech.esper.epl.expression.ExprNodeUtility;
import com.espertech.esper.view.*;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.util.List;
import java.util.Set;

/**
 * Factory for {@link GroupByView} instances.
 */
public class GroupByViewFactory implements ViewFactory, GroupByViewFactoryMarker
{
    private static Log log = LogFactory.getLog(GroupByViewFactory.class);

    /**
     * View parameters.
     */
    protected List<ExprNode> viewParameters;

    /**
     * List of criteria expressions.
     */
    protected ExprNode[] criteriaExpressions;

    private EventType eventType;

    protected boolean isReclaimAged;
    protected double reclaimMaxAge;
    protected double reclaimFrequency;

    public void setViewParameters(ViewFactoryContext viewFactoryContext, List<ExprNode> expressionParameters) throws ViewParameterException
    {
        this.viewParameters = expressionParameters;

        Hint reclaimGroupAged = HintEnum.RECLAIM_GROUP_AGED.getHint(viewFactoryContext.getStatementContext().getAnnotations());

        if (reclaimGroupAged != null) {
            isReclaimAged = true;
            String hintValueMaxAge = HintEnum.RECLAIM_GROUP_AGED.getHintAssignedValue(reclaimGroupAged);
            if (hintValueMaxAge == null)
            {
                throw new ViewParameterException("Required hint value for hint '" + HintEnum.RECLAIM_GROUP_AGED + "' has not been provided");
            }
            try {
                reclaimMaxAge = Double.parseDouble(hintValueMaxAge);
            }
            catch (RuntimeException ex) {
                throw new ViewParameterException("Required hint value for hint '" + HintEnum.RECLAIM_GROUP_AGED + "' value '" + hintValueMaxAge + "' could not be parsed as a double value");
            }

            String hintValueFrequency = HintEnum.RECLAIM_GROUP_FREQ.getHintAssignedValue(reclaimGroupAged);
            if (hintValueFrequency == null)
            {
                reclaimFrequency = reclaimMaxAge;
            }
            else {
                try {
                    reclaimFrequency = Double.parseDouble(hintValueFrequency);
                }
                catch (RuntimeException ex) {
                    throw new ViewParameterException("Required hint value for hint '" + HintEnum.RECLAIM_GROUP_FREQ + "' value '" + hintValueFrequency + "' could not be parsed as a double value");
                }
            }
            if (reclaimMaxAge < 0.100) {
                log.warn("Reclaim max age parameter is less then 100 milliseconds, are your sure?");
            }

            if (log.isDebugEnabled()) {
                log.debug("Using reclaim-aged strategy for group-window age " + reclaimMaxAge + " frequency " + reclaimFrequency);
            }
        }
    }

    public void attach(EventType parentEventType, StatementContext statementContext, ViewFactory optionalParentFactory, List<ViewFactory> parentViewFactories) throws ViewParameterException
    {
        criteriaExpressions = ViewFactorySupport.validate("Group-by view", parentEventType, statementContext, viewParameters, false);

        if (criteriaExpressions.length == 0)
        {
            String errorMessage = "Unique-by view requires a one or more expressions provinding unique values as parameters";
            throw new ViewParameterException(errorMessage);
        }

        this.eventType = parentEventType;
    }

    /**
     * Returns the names of fields to group by
     * @return field names
     */
    public ExprNode[] getCriteriaExpressions()
    {
        return criteriaExpressions;
    }

    public View makeView(AgentInstanceViewFactoryChainContext agentInstanceViewFactoryContext)
    {
        if (isReclaimAged) {
            return new GroupByViewReclaimAged(agentInstanceViewFactoryContext, criteriaExpressions, ExprNodeUtility.getEvaluators(criteriaExpressions), reclaimMaxAge, reclaimFrequency);
        }
        return new GroupByViewImpl(agentInstanceViewFactoryContext, criteriaExpressions, ExprNodeUtility.getEvaluators(criteriaExpressions));
    }

    public EventType getEventType()
    {
        return eventType;
    }

    public boolean canReuse(View view)
    {
        if (!(view instanceof GroupByView))
        {
            return false;
        }

        if (isReclaimAged) {
            return false;
        }

        GroupByView myView = (GroupByView) view;
        if (!ExprNodeUtility.deepEquals(myView.getCriteriaExpressions(), criteriaExpressions))
        {
            return false;
        }

        return true;
    }
}