Flink报错：No operators defined in streaming topology. Cannot execute.

报错描述

在用Flink进行Flink SQL相关的测试的时候，报了以下错误：

Exception in thread "main" java.lang.RuntimeException: java.lang.IllegalStateException: No operators defined in streaming topology. Cannot execute.
    at com.gitee.xxx.flink.learning.udf.UDFExample.main(UDFExample.java:46)
Caused by: java.lang.IllegalStateException: No operators defined in streaming topology. Cannot execute.
    at org.apache.flink.streaming.api.environment.StreamExecutionEnvironment.getStreamGraphGenerator(StreamExecutionEnvironment.java:2019)
    at org.apache.flink.streaming.api.environment.StreamExecutionEnvironment.getStreamGraph(StreamExecutionEnvironment.java:2010)
    at org.apache.flink.streaming.api.environment.StreamExecutionEnvironment.getStreamGraph(StreamExecutionEnvironment.java:1995)
    at org.apache.flink.streaming.api.environment.StreamExecutionEnvironment.execute(StreamExecutionEnvironment.java:1834)
    at com.gitee.xxx.flink.learning.udf.UDFExample.main(UDFExample.java:44)

问题原因

    在整个代码中没有流算子的存在，因为都是使用table sql的数据类型。

解决办法

    当没有流的存在时，不要在代码的最后加上env.execute()。

//      try {
//          env.execute("UDF Example");
//      } catch (Exception e) {
//          throw new RuntimeException(e);
//      }

其它

其实报错也没问题，照样能运行