FirstTimeViewFactory.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.window;

import com.espertech.esper.client.EventType;
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.util.JavaClassHelper;
import com.espertech.esper.view.*;

import java.util.List;

/**
 * Factory for {@link FirstTimeView}.
 */
public class FirstTimeViewFactory implements AsymetricDataWindowViewFactory, DataWindowBatchingViewFactory
{
    private EventType eventType;

    /**
     * Number of msec before expiry.
     */
    protected long millisecondsBeforeExpiry;

    public void setViewParameters(ViewFactoryContext viewFactoryContext, List<ExprNode> expressionParameters) throws ViewParameterException
    {
        List<Object> viewParameters = ViewFactorySupport.validateAndEvaluate("Time first view", viewFactoryContext.getStatementContext(), expressionParameters);
        String errorMessage = "Time first view requires a single numeric or time period parameter";
        if (viewParameters.size() != 1)
        {
            throw new ViewParameterException(errorMessage);
        }

        Object parameter = viewParameters.get(0);
        if (!(parameter instanceof Number))
        {
            throw new ViewParameterException(errorMessage);
        }
        else
        {
            Number param = (Number) parameter;
            if (JavaClassHelper.isFloatingPointNumber(param))
            {
                millisecondsBeforeExpiry = Math.round(1000d * param.doubleValue());
            }
            else
            {
                millisecondsBeforeExpiry = 1000 * param.longValue();
            }
        }

        if (millisecondsBeforeExpiry < 1)
        {
            throw new ViewParameterException("Time first view requires a size of at least 1 msec");
        }
    }

    public void attach(EventType parentEventType, StatementContext statementContext, ViewFactory optionalParentFactory, List<ViewFactory> parentViewFactories) throws ViewParameterException
    {
        this.eventType = parentEventType;
    }

    public View makeView(AgentInstanceViewFactoryChainContext agentInstanceViewFactoryContext)
    {
        return new FirstTimeView(this, agentInstanceViewFactoryContext, millisecondsBeforeExpiry);
    }

    public EventType getEventType()
    {
        return eventType;
    }

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

        FirstTimeView myView = (FirstTimeView) view;
        if (myView.getMsecIntervalSize() != millisecondsBeforeExpiry)
        {
            return false;
        }

        return myView.isEmpty();
    }
}