flink的默认窗口触发机制_flink triggercontext ctx.getcurrentwatermark

我们以滑动窗口为列，程序采用eventTime，直接上源码：

@PublicEvolving
public class EventTimeTrigger extends Trigger<Object, TimeWindow> {
   
	private static final long serialVersionUID = 1L;

	private EventTimeTrigger() {
   }

	@Override
	public TriggerResult onElement(Object element, long timestamp, TimeWindow window, TriggerContext ctx) throws Exception {
   
		if (window.maxTimestamp() <= ctx.getCurrentWatermark()) {
   
			// if the watermark is already past the window fire immediately
			return TriggerResult.FIRE;
		}<
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