Question

{
 "event": {
  "header":{ 
   "name":"abc",
   "version":"1.0",
   "producer":"123",
   "channel":"lab",
   "countryCode":"US"
  },
  "body":{
   "customerIdentifiers":[ 
    {"customerIdentifier":"1234","customerIdType":"cc"},
    {"customerIdentifier":"234", "customerIdType":"id"}
   ],
   "accountIdentifiers":[
    {"accountIdentifier":"123",    "accountIdType":"no"}, 
    {"accountIdentifier":"Primary","accountIdType":"da"}
   ],
   "eventDetails":{
    "transactionDateTime":"2019-03-26 05:28:13.000",
    "transactionDate":"2019-03-26",
    "monthAverage":"188",
    "dailyAverage":"7"
   }
  }
 }
}

为上述json创建流：

CREATE STREAM STREAM_NAME(
  event STRUCT<
    header STRUCT<
      name VARCHAR,
      version VARCHAR,
      producer VARCHAR,
      channel VARCHAR,
      countryCode VARCHAR
      eventTimeStamp VARCHAR
    >,
    body STRUCT<
      customerIdentifiers STRUCT<
         customerIdentifier VARCHAR,
         customerIdType VARCHAR
      >,
      accountIdentifiers STRUCT<
         accountIdentifier VARCHAR,
         accountIdType VARCHAR
      >,                            
      eventDetails STRUCT<
         transactionDateTime VARCHAR,
         transactionDate VARCHAR,
         productDescription VARCHAR,
         monthAverage VARCHAR,
         dailyAverage VARCHAR
      >
    >
  >
) WITH (
  KAFKA_TOPIC = 'TOPIC1',
  VALUE_FORMAT = 'JSON',
  PARTITIONS = 1
  ;

我无法从流中读取消息：

select * from STREAM_NAME emit changes;

有什么建议吗？

Answer 1

您可能会遇到反序列化错误，因为您创建的流的架构与数据的架构不匹配。

重新格式化示例数据和SQL时，错误变得更加明显：

$.event.body.customerIdentifiers元素是一个结构数组，但DDL将其定义为一个结构。
$.event.body.accountIdentifiers元素是一个结构数组，但DDL将其定义为一个结构。

应该起作用的DDL是：

CREATE STREAM STREAM_NAME(
  event STRUCT<
    header STRUCT<
      name VARCHAR,
      version VARCHAR,
      producer VARCHAR,
      channel VARCHAR,
      countryCode VARCHAR
      eventTimeStamp VARCHAR
    >,
    body STRUCT<
      customerIdentifiers ARRAY<STRUCT<
         customerIdentifier VARCHAR,
         customerIdType VARCHAR
      >>,
      accountIdentifiers ARRAY<STRUCT<
         accountIdentifier VARCHAR,
         accountIdType VARCHAR
      >>,                            
      eventDetails STRUCT<
         transactionDateTime VARCHAR,
         transactionDate VARCHAR,
         productDescription VARCHAR,
         monthAverage VARCHAR,
         dailyAverage VARCHAR
      >
    >
  >
) WITH (
  KAFKA_TOPIC = 'TOPIC1',
  VALUE_FORMAT = 'JSON',
  PARTITIONS = 1
  ;

还请注意，数据不包含DDL中的以下内容（尽管这不会引起任何问题，因为字段仅为NULL）：

$.event.header.eventTimeStamp
$.event.body.eventDetails.productDescription

无法从ksqldb中的kafka主题读取消息

1 个答案: