Flink 嵌套类 toDataStream 转换错误

如何解决Flink 嵌套类 toDataStream 转换错误

我使用的是 flink 1.13。我正在尝试以下列方式将表结果转换为数据流，但一直出错。

public class HybridTrial {
  public static class Address {
    public String street;
    public String houseNumber;

    public Address() {}

    public Address(String street,String houseNumber) {
      this.street = street;
      this.houseNumber = houseNumber;
    }
  }

  public static class User {
    public String name;

    public Integer score;

    public LocalDateTime event_time;

    public Address address;

    // default constructor for DataStream API
    public User() {}

    // fully assigning constructor for Table API
    public User(String name,Integer score,LocalDateTime event_time,Address address) {
      this.name = name;
      this.score = score;
      this.event_time = event_time;
      this.address = address;
    }
  }

  public static void main(String[] args) throws Exception {
    StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
    DataStream<User> dataStream =
        env.fromElements(
                new User("Alice",4,LocalDateTime.Now(),new Address()),new User("Bob",6,new Address("NBC","204")),new User("Alice",10,new Address("ABC","1033")))
            .assignTimestampsAndWatermarks(
                WatermarkStrategy.<User>forBoundedOutOfOrderness(Duration.ofSeconds(60)));

    StreamTableEnvironment tableEnv = StreamTableEnvironment.create(env);
    Table table =
        tableEnv.fromDataStream(
            dataStream,Schema.newBuilder().build());

    table.printSchema();

    Table t = table.select($("*"));

    DataStream<User> dsRow = tableEnv.toDataStream(t,User.class);
    dsRow.print();

    env.execute();
  }
}

我得到的错误是：

Exception in thread "main" org.apache.flink.table.api.ValidationException: Column types of query result and sink for registered table 'default_catalog.default_database.Unregistered_DataStream_Sink_1' do not match.
Cause: Incompatible types for sink column 'event_time' at position 2.

Query schema: [name: STRING,score: INT,event_time: RAW('java.time.LocalDateTime','...'),address: *flinksqlExperiments.HybridTrial$Address<`street` STRING,`houseNumber` STRING>*]
Sink schema:  [name: STRING,event_time: TIMESTAMP(9),`houseNumber` STRING>*]
    at org.apache.flink.table.planner.connectors.DynamicSinkUtils.createSchemaMismatchException(DynamicSinkUtils.java:437)
    at org.apache.flink.table.planner.connectors.DynamicSinkUtils.validateSchemaAndApplyImplicitCast(DynamicSinkUtils.java:256)
    at org.apache.flink.table.planner.connectors.DynamicSinkUtils.convertSinkToRel(DynamicSinkUtils.java:198)
    at org.apache.flink.table.planner.connectors.DynamicSinkUtils.convertExternalToRel(DynamicSinkUtils.java:143)

我也尝试过从 DataStream 到 table 的自定义转换，但是在从 table 转换到 DataStream 时仍然遇到错误。我被卡住了，所以感谢任何帮助。

解决方法

DataStream 中基于反射的自动类型提取不如 Table API 强大。这也是由于 DataStream API 中的状态向后兼容性问题。

Traceback (most recent call last): File "C:\Users\Ankit Chawrai\anaconda3\Scripts\jupyter-notebook-script.py",line 6,in <module> from notebook.notebookapp import main File "C:\Users\Ankit Chawrai\anaconda3\lib\site-packages\notebook\notebookapp.py",line 51,in <module> from zmq.eventloop import ioloop File "C:\Users\Ankit Chawrai\anaconda3\lib\site-packages\zmq\__init__.py",line 50,in <module> from zmq import backend File "C:\Users\Ankit Chawrai\anaconda3\lib\site-packages\zmq\backend\__init__.py",line 40,in <module> reraise(*exc_info) File "C:\Users\Ankit Chawrai\anaconda3\lib\site-packages\zmq\utils\sixcerpt.py",line 34,in reraise raise value File "C:\Users\Ankit Chawrai\anaconda3\lib\site-packages\zmq\backend\__init__.py",line 27,in <module> _ns = select_backend(first) File "C:\Users\Ankit Chawrai\anaconda3\lib\site-packages\zmq\backend\select.py",line 28,in select_backend mod = __import__(name,fromlist=public_api) File "C:\Users\Ankit Chawrai\anaconda3\lib\site-packages\zmq\backend\cython\__init__.py",in <module> from . import (constants,error,message,context,ImportError: DLL load failed while importing error: The specified module could not be found.``` 字段是 DataStream API 中的 event_time，它导致 Table API 中的 GenericType。您有以下几种可能：

• 在 RAW 中给出正确的 TypeInformation
• 使用 fromElements 中的 TypeInformation 覆盖 DataType