Avro格式Kafka消息创建报错：Expected start-union. Got VALUE_STRING 求助

我正在使用以下Avro Schema测试Avro格式数据：

{
    "namespace": "de.leyland.audit",
    "type": "record",
    "name": "AuditDataChangeleyland",
    "fields": [
        {"name": "machineID",  "type": "string"},
        {"name": "correlationId",  "type": "string"},
        {"name": "timestamp",  "type": "long", "logicalType": "timestamp-millis"},
        {"name": "machinescreen","type":{"type": "enum", "name": "BlockScreen", "symbols": ["NO","YES"]}},
        {"name": "entitlements", "type": ["null",{
            "type": "array",
            "items": {
                "name": "entitlements",
                "type": "record",
                "fields": [
                    {
                        "name": "name",
                        "type": "string"
                    }
                ]
            }
        }]}
    ]
}

尝试基于该Schema创建供Kafka消费者使用的JSON格式测试数据时出现报错，测试用JSON如下：

{
  "machineID": "ahdzeha46",
  "correlationId": "473363621",
  "timestamp": "2021-08-09T12:20:15",
  "machinescreen": "NO",
  "correlationId": "corr-473363621",
  "entitlements": [
    {
      "entitlements": "machinerepair"
    }
  ]
}

报错信息：

Caused by: org.apache.avro.AvroTypeException: Expected start-union. Got VALUE_STRING

请问如何修正并生成正确的测试数据？

你的测试数据存在4个关键问题，逐一修正即可解决报错：

• Union类型处理错误：entitlements是["null", array]的Union类型，Avro JSON要求Union类型数据必须用带类型标识的对象包裹（null除外），你直接传数组不符合规则。
• 数组内部结构不匹配：Schema中数组的items是含name字段的record，但你用了entitlements作为键名，结构完全不符。
• 时间戳类型错误：timestamp定义为毫秒级时间戳（long类型），不能传ISO格式字符串，需传入数值。
• 重复字段冗余：测试数据重复定义了correlationId，需删除其中一个。

如果要传入有值的entitlements，正确格式如下：

{
  "machineID": "ahdzeha46",
  "correlationId": "corr-473363621",
  "timestamp": 1628506815000,
  "machinescreen": "NO",
  "entitlements": {
    "array": [
      {
        "name": "machinerepair"
      }
    ]
  }
}

如果要传入null值的entitlements，可以写成：

{
  "machineID": "ahdzeha46",
  "correlationId": "corr-473363621",
  "timestamp": 1628506815000,
  "machinescreen": "NO",
  "entitlements": null
}

内容的提问来源于stack exchange，提问作者data2quest