Flink问题记录：A raw type backed by type information has no serializable string representation. It ....

问题原因：table转成stream，table中字段要和stream字段类型一致，如果不一致，就会报上述的错误。其实就是table是什么类型，转回流时还是必须这个类型。

示例：

StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
StreamTableEnvironment tableEnv = StreamTableEnvironment.getTableEnvironment(env);
DataStream> sourceStream = env.addSource(kafkaSource);
//注册表时时两个字段
Table table = tableEnv.registerDataStream("tableName", sourceStream);
//转成流时类型为tuple1，只有一个字段，不匹配，应转成tuple2
DataStream> sinkStream = tableEnv.toAppendStream(table, Tuple1.class);