Time Window：

Length Window：

Time Batch Window：

帶batch的是所有的都執行完後，在觸發UpdateListener，如下邊例子：

public class AppleListener implements UpdateListener {

    public void update(EventBean[] newEvents, EventBean[] oldEvents) {
        if (newEvents != null) {
            Double avg 
 
= (Double)newEvents[0].get("avg(price)");
            System.out.println("Apple‘s average price is " + avg);
        }
    }

}

        String product = Apple.class.getName();
        String epl = "select avg(price) from " + product + ".win:length_batch(3)";

        EPStatement state 
 
= admin.createEPL(epl);
        state.addListener(new AppleListener());

        EPRuntime runtime = epService.getEPRuntime();

        Apple apple1 = new Apple();
        apple1.setId(1);
        apple1.setPrice(5);
        runtime.sendEvent(apple1);

        Apple apple2 = new Apple();
        apple2.setId(
 
2);
        apple2.setPrice(2);
        runtime.sendEvent(apple2);

        Apple apple3 = new Apple();
        apple3.setId(3);
        apple3.setPrice(5);
        runtime.sendEvent(apple3);

esper（1）-窗口概述