org.apache.avro.AvroTypeException: 未知联合分支

Question

我正在使用这个 Avro 模式：

价格-state.avsc

{
    "namespace": "com.company.model",
    "name": "Product",
    "type": "record",
    "fields": [
        {
            "name": "product_id",
            "type": "string"
        },
        {
            "name": "sale_prices",
            "type": {
                "name": "sale_prices",
                "type": "record",
                "fields": [
                    {
                        "name": "default",
                        "type": {
                            "name": "default",
                            "type": "record",
                            "fields": [
                                {
                                    "name": "order_by_item_price_by_item",
                                    "type": [
                                        "null",
                                        {
                                            "name": "markup_strategy",
                                            "type": "record",
                                            "fields": [
                                                {
                                                    "name": "type",
                                                    "type": {
                                                        "name": "type",
                                                        "type": "enum",
                                                        "symbols": ["margin", "sale_price"]
                                                    }
                                                }
                                            ]
                                        }
                                    ]
                                },
                                {"name": "order_by_item_price_by_weight", "type": ["null", "string"]},
                                {"name": "order_by_weight_price_by_weight", "type": ["null", "string"]}
                            ]
                        }
                    }
                ]
            }
        }
    ]
}

它在 this website 上正确验证，所以我假设架构有效。

我在构建 JSON 文件时遇到问题，然后应使用上述架构对其进行编码。

我正在使用这个 JSON 进行一些测试：

test.json

{
    "product_id": "123",
    "sale_prices": {
        "default": {
            "order_by_item_price_by_item": {
                "markup_strategy": {
                    "type": {"enum": "margin"}
                }
            },
            "order_by_item_price_by_weight": null,
            "order_by_weight_price_by_weight": null
        }
    }
}

当 运行 java -jar avro-tools-1.8.2.jar fromjson --schema-file prices-state.avsc test.json 我得到：

Exception in thread "main" org.apache.avro.AvroTypeException: Unknown union branch markup_strategy

我读到 here 由于 JSON 编码，我必须将东西包装在联合内，所以我尝试了不同的组合，但似乎没有一个有效。

Answer 1

这是一个 命名空间 解析问题。以这个简化的模式为例：

test.avsc

{
    "name": "Product",
    "type": "record",
    "fields": [
        {
            "name": "order_by_item_price_by_item",
            "type": [
                "null",
                {
                    "type": "record",
                    "name": "markup_strategy",
                    "fields": [{
                        "name": "type",
                        "type": {
                            "name": "type",
                            "type": "enum",
                            "symbols": ["margin", "sale_price"]
                        }
                    }]
                }
            ]
        }
    ]
}

使用下面的 JSON 它验证得很好

test.json

{
    "order_by_item_price_by_item": {
        "markup_strategy": {
            "type": "margin"
        }
    }
}

现在，如果您要在架构之上添加名称空间，例如

test.avsc

{
    "namespace": "test",
    "name": "Product",
    "type": "record",
    "fields": [
    ...

然后你需要改变你的test.json或者你会得到

Exception in thread "main" org.apache.avro.AvroTypeException: Unknown union branch markup_strategy

final_test.json

{
    "order_by_item_price_by_item": {
        "test.markup_strategy": {
            "type": "margin"
        }
    }
}

因此，当在联合类型中并且您正在 JSON 对使用用户指定名称的 Avro 命名类型（记录、固定或枚举）进行编码时，需要在该类型的名称前添加命名空间名称也用于解析。

更多关于 namespaces and JSON encoding。

Answer 2

Francesco 的回答很好，解释了问题！
以防万一有人（甚至是我未来的自己） 需要另一个带有 optional 字段和 namespaces:

的示例

1. 架构 - WhosebugSchema.avsc

{
  "type": "record",
  "name": "WhosebugExampleSchema",
  "namespace": "com.schemata.Whosebug",
  "fields": [
    {
      "name": "exampleEntity",
      "type": {
        "type": "record",
        "name": "ExampleEntity",
        "namespace": "com.Whosebug",
        "fields": [
          {
            "name": "description",
            "type": ["null", "string"]
          },
          {
            "name": "currentAmount",
            "type": {
              "type": "record",
              "name": "MonetaryAmount",
              "namespace": "com.acme.common",
              "fields": [
                {
                  "name": "currencyCode",
                  "type": ["null", {
                    "type": "enum",
                      "name": "CurrencyCode",
                      "symbols": ["AED", "USD"],
                      "default": "USD"
                    }
                  ]
                },
                {
                  "name": "amount",
                  "type": {
                    "type": "int"
                  }
                }
              ]
            }
          },
          {
            "name": "totalAmount",
            "type": ["null", "com.acme.common.MonetaryAmount"]
          }
        ]
      }
    }
  ]
}

2. 示例文件 - Whosebug.json

{
  "exampleEntity": {
    "description": {
      "string": "some optional description"
    },
    "currentAmount":{
      "amount": 10",
      "currencyCode": {
        "com.acme.common.CurrencyCode": "USD"
      }
    },
    "totalAmount": {
      "com.acme.common.MonetaryAmount": {
        "amount": 20,
        "currencyCode": {
          "com.acme.common.CurrencyCode": "USD"
        }
      }
    }
  }
}

currentAmount 和 totalAmount 都有 com.acme.common.MonetaryAmount 类型。
虽然前者是必填字段，但后者可以是 null.
同样在 MonetaryAmount 中，我们有 required (amount) 和 optional (currencyCode).
以下命令生成 avro 消息：

java -jar avro-tools-1.11.0.jar fromjson --schema-file ./WhosebugSchema.avsc Whosebug.json > Whosebug.avro