org.apache.flink.table.api.ValidationException: Expected LocalReferenceExpression. Got: timestamp

flink.table.api.ValidationException: Expected LocalReferenceExpression. Got: timestamp"/>

org.apache.flink.table.api.ValidationException: Expected LocalReferenceExpression. Got: timestamp

情景：在设置滑动窗口时遇到的问题：Expected LocalReferenceExpression. Got: timestamp，详细代码如下：

Table table = tableEnv.fromDataStream(stream);
table
.window(Slide.over(lit(1).hours()).every(lit(5).minutes()).on(($("timestamp").rowtime()).as("ts")).as("w"))
.groupBy($("w"), $("itemId"))
.select($("itemId"), $("itemId").count().as("itemCount"), $("w").end().as("windowEnd"))
.window(Over.partitionBy($("windowEnd")).orderBy($("itemCount").desc()).as("row_num"))
.select($("itemId"), $("itemCount"), $("windowEnd"))
.where($("row_num").between(0, 3));

原因是：需要在定义表设置事件时间，在表API中不能设置事件时间。
原来代码修改为：

Table table = tableEnv.fromDataStream(stream,$("itemId"),$("timestamp").rowtime().as("ts"));
Table tableResult =table.window(Slide.over(lit(1).hours()).every(lit(5).minutes()).on($("ts")).as("w")).groupBy($("w"), $("itemId")).select($("itemId"), $("itemId").count().as("itemCount"), $("w").end().as("windowEnd")).window(Over.partitionBy($("windowEnd")).orderBy($("itemCount").desc()).as("rank")).select($("itemId"), $("itemCount"), $("windowEnd")).where($("row_num").between(0, 3));