Java tutorial
/************************************************************************************** * 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.filter; import com.espertech.esper.client.EventBean; import com.espertech.esper.epl.expression.ExprEvaluator; import com.espertech.esper.epl.expression.ExprEvaluatorContext; import com.espertech.esper.epl.expression.ExprNode; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; public class ExprNodeAdapterBase { private static final Log log = LogFactory.getLog(ExprNodeAdapterBase.class); protected final String statementName; protected final ExprNode exprNode; protected final ExprEvaluator exprNodeEval; protected final ExprEvaluatorContext evaluatorContext; /** * Ctor. * @param exprNode is the boolean expression */ public ExprNodeAdapterBase(String statementName, ExprNode exprNode, ExprEvaluatorContext evaluatorContext) { this.statementName = statementName; this.exprNode = exprNode; this.exprNodeEval = exprNode.getExprEvaluator(); this.evaluatorContext = evaluatorContext; } /** * Evaluate the boolean expression given the event as a stream zero event. * * @param theEvent is the stream zero event (current event) * @return boolean result of the expression */ public boolean evaluate(EventBean theEvent) { return evaluatePerStream(new EventBean[] { theEvent }); } protected boolean evaluatePerStream(EventBean[] eventsPerStream) { try { Boolean result = (Boolean) exprNodeEval.evaluate(eventsPerStream, true, this.evaluatorContext); if (result == null) { return false; } return result; } catch (RuntimeException ex) { log.error("Error evaluating expression '" + exprNode.toExpressionString() + "' statement '" + statementName + "': " + ex.getMessage(), ex); return false; } } }