【问题标题】:How to parse newline delimited JSON with retrofit and moshi?如何使用改造和 moshi 解析换行符分隔的 JSON?
【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

标签: android json retrofit moshi ndjson


【解决方案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 ")

【讨论】:

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