如何使用改造和 moshi 解析换行符分隔的 JSON？

Posted 2023-03-22

【中文标题】如何使用改造和 moshi 解析换行符分隔的 JSON？

【英文标题】：How to parse newline delimited JSON with retrofit and moshi?

【发布时间】：2021-06-27 15:27:41

【问题描述】：

我正在尝试使用改造和 moshi 解析换行符分隔的 json。这是我的 GET 函数：

suspend fun getDeviceValuesNew(@Path("application-id") applicationId: String, @Path("device-id") deviceId: String) 
: Response<List<ValueApiResponse>>

当我尝试运行它时，我得到了这个错误：

 com.squareup.moshi.JsonDataException: Expected BEGIN_ARRAY but was BEGIN_OBJECT at path $

HTTP 调用返回的 json 格式如下：

    "result": 
        "end_device_ids": 
            "device_id": "esp32",
            "application_ids": 
        ,
        "received_at": "2021-03-31T11:33:42.757281753Z",
        "uplink_message": 
            "decoded_payload": 
                "brightness": 0
            ,
            "settings": 
                "data_rate": 
            ,
            "received_at": "2021-03-31T11:33:42.547285090Z"
        
    


    "result": 
        "end_device_ids": 
            "device_id": "esp32",
            "application_ids": 
        ,
        "received_at": "2021-03-31T11:18:17.745921472Z",
        "uplink_message": 
            "decoded_payload": 
                "brightness": 0
            ,
            "settings": 
                "data_rate": 
            ,
            "received_at": "2021-03-31T11:18:17.538276218Z"
        
    

编辑#1： 正如您在下面的回答中看到的那样，我设法从 API 获得了有效的 JSON 响应，但我仍在努力将这些 JSON 对象解析为 Kotlin 对象列表。 如何让 Moshi 将这些换行符分隔的 JSON 对象作为列表处理？ 我认为问题在于 Moshi 需要将对象包装在数组中才能被识别为列表。我该怎么做？

这是我用来解析的数据类：

@JsonClass(generateAdapter = true)
data class ValueDto(
    @Json(name = "result")
    val result: Result
) 
    @JsonClass(generateAdapter = true)
    data class Result(
        @Json(name = "end_device_ids")
        val endDeviceIds: EndDeviceIds,
        @Json(name = "received_at")
        val receivedAt: String,
        @Json(name = "uplink_message")
        val uplinkMessage: UplinkMessage
    ) 
        @JsonClass(generateAdapter = true)
        data class EndDeviceIds(
            @Json(name = "application_ids")
            val applicationIds: ApplicationIds,
            @Json(name = "device_id")
            val deviceId: String
        ) 
            @JsonClass(generateAdapter = true)
            class ApplicationIds(
            )
        

        @JsonClass(generateAdapter = true)
        data class UplinkMessage(
            @Json(name = "decoded_payload")
            val decodedPayload: DecodedPayload,
            @Json(name = "received_at")
            val receivedAt: String,
            @Json(name = "settings")
            val settings: Settings
        ) 
            @JsonClass(generateAdapter = true)
            data class DecodedPayload(
                @Json(name = "brightness")
                val brightness: Int
            )
            @JsonClass(generateAdapter = true)
            data class Settings(
                @Json(name = "data_rate")
                val dataRate: DataRate
            ) 
                @JsonClass(generateAdapter = true)
                class DataRate(
                )
            
        
    

【问题讨论】：

那不是有效的 json，因此您将不得不以某种方式拆分对象，我真的不知道您将如何做到这一点，因为每一行都有一个换行符。通常是这样的，每个对象后面只有一个换行符，所以你在换行符上拆分，你得到每个对象

【参考方案1】：

@tyczj 是对的，这不是有效的 ndjson，因为在 ndjson 中，换行符只出现在每个单独的 json 文本之后。解决方案是使用 HTTP 请求发送Accept: text/event-stream，现在我得到一个有效的 ndjson 响应，如下所示：

"result":"end_device_ids":"device_id":"esp32-bh1750","application_ids":,"received_at":"2021-04-24T10:19:04.021238048Z","uplink_message":"decoded_payload":"brightness":0,"settings":"data_rate":,"received_at":"2021-04-24T10:19:03.809173924Z"

"result":"end_device_ids":"device_id":"esp32-bh1750","application_ids":,"received_at":"2021-04-24T10:25:22.260712161Z","uplink_message":"decoded_payload":"brightness":119,"settings":"data_rate":,"received_at":"2021-04-24T10:25:22.046086937Z"

"result":"end_device_ids":"device_id":"esp32-bh1750","application_ids":,"received_at":"2021-04-24T10:18:58.438947740Z","uplink_message":"decoded_payload":"brightness":0,"settings":"data_rate":,"received_at":"2021-04-24T10:18:58.228671174Z"

"result":"end_device_ids":"device_id":"esp32-bh1750","application_ids":,"received_at":"2021-04-24T10:21:10.102303310Z","uplink_message":"decoded_payload":"brightness":106,"settings":"data_rate":,"received_at":"2021-04-24T10:21:09.893217735Z"

"result":"end_device_ids":"device_id":"esp32-bh1750","application_ids":,"received_at":"2021-04-24T10:23:16.177064041Z","uplink_message":"decoded_payload":"brightness":108,"settings":"data_rate":,"received_at":"2021-04-24T10:23:15.967959055Z"

"result":"end_device_ids":"device_id":"esp32-bh1750","application_ids":,"received_at":"2021-04-24T10:27:28.334312076Z","uplink_message":"decoded_payload":"brightness":117,"settings":"data_rate":,"received_at":"2021-04-24T10:27:28.126104222Z"

"result":"end_device_ids":"device_id":"esp32-bh1750","application_ids":,"received_at":"2021-04-24T10:29:34.400253264Z","uplink_message":"decoded_payload":"brightness":99,"settings":"data_rate":,"received_at":"2021-04-24T10:29:34.190980301Z"

"result":"end_device_ids":"device_id":"esp32-bh1750","application_ids":,"received_at":"2021-04-24T10:31:40.481766225Z","uplink_message":"decoded_payload":"brightness":118,"settings":"data_rate":,"received_at":"2021-04-24T10:31:40.270452429Z"

"result":"end_device_ids":"device_id":"esp32-bh1750","application_ids":,"received_at":"2021-04-24T10:33:46.567235913Z","uplink_message":"decoded_payload":"brightness":114,"settings":"data_rate":,"received_at":"2021-04-24T10:33:46.357373037Z"

"result":"end_device_ids":"device_id":"esp32-bh1750","application_ids":,"received_at":"2021-04-24T10:35:52.737386496Z","uplink_message":"decoded_payload":"brightness":121,"settings":"data_rate":,"received_at":"2021-04-24T10:35:52.426583804Z"

我已经通过改造注释添加了标题： @Headers("Accept: text/event-stream ")