//参考官网指定时间戳，直接使用lambda表达式获取
WatermarkStrategy.<Tuple3<Long,String,Integer>>forBoundedOutOfOrderness(Duration.ofSeconds(20))
.withTimestampAssigner((event,timestamp) -> event.f0) ;
参考：
https://ci.apache.org/projects/flink/flink-docs-release-1.12/zh/dev/event_timestamps_watermarks.html