Retrofit2とMoshiを用いてJSONオブジェクトに対応したPOJOを作成したい

Question

Retorfit2とMoshiを用いてlivedoorの天気APIを利用して、天気情報を取得したいです。以下のコードを実行したところ以下のエラーがエミュレーターに表示され、取得できません。どこを直せばよいか教えてください。
expected begin_array but was begin_object at path $

どこを直せばよいか教えてください。

以下のJSONオブジェクトを変換させようとしています。

{
  "pinpointLocations": [
    {
      "link": "http://weather.livedoor.com/area/forecast/2710000",
      "name": "大阪市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2714000",
      "name": "堺市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2720200",
      "name": "岸和田市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2720300",
      "name": "豊中市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2720400",
      "name": "池田市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2720500",
      "name": "吹田市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2720600",
      "name": "泉大津市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2720700",
      "name": "高槻市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2720800",
      "name": "貝塚市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2720900",
      "name": "守口市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2721000",
      "name": "枚方市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2721100",
      "name": "茨木市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2721200",
      "name": "八尾市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2721300",
      "name": "泉佐野市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2721400",
      "name": "富田林市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2721500",
      "name": "寝屋川市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2721600",
      "name": "河内長野市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2721700",
      "name": "松原市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2721800",
      "name": "大東市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2721900",
      "name": "和泉市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2722000",
      "name": "箕面市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2722100",
      "name": "柏原市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2722200",
      "name": "羽曳野市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2722300",
      "name": "門真市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2722400",
      "name": "摂津市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2722500",
      "name": "高石市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2722600",
      "name": "藤井寺市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2722700",
      "name": "東大阪市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2722800",
      "name": "泉南市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2722900",
      "name": "四條畷市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2723000",
      "name": "交野市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2723100",
      "name": "大阪狭山市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2723200",
      "name": "阪南市"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2730100",
      "name": "島本町"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2732100",
      "name": "豊能町"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2732200",
      "name": "能勢町"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2734100",
      "name": "忠岡町"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2736100",
      "name": "熊取町"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2736200",
      "name": "田尻町"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2736600",
      "name": "岬町"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2738100",
      "name": "太子町"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2738200",
      "name": "河南町"
    },
    {
      "link": "http://weather.livedoor.com/area/forecast/2738300",
      "name": "千早赤阪村"
    }
  ],
  "link": "http://weather.livedoor.com/area/forecast/270000",
  "forecasts": [
    {
      "dateLabel": "今日",
      "telop": "雨時々曇",
      "date": "2020-03-28",
      "temperature": {
        "min": null,
        "max": {
          "celsius": "14",
          "fahrenheit": "57.2"
        }
      },
      "image": {
        "width": 50,
        "url": "http://weather.livedoor.com/img/icon/17.gif",
        "title": "雨時々曇",
        "height": 31
      }
    },
    {
      "dateLabel": "明日",
      "telop": "曇時々雨",
      "date": "2020-03-29",
      "temperature": {
        "min": {
          "celsius": "8",
          "fahrenheit": "46.4"
        },
        "max": {
          "celsius": "15",
          "fahrenheit": "59.0"
        }
      },
      "image": {
        "width": 50,
        "url": "http://weather.livedoor.com/img/icon/10.gif",
        "title": "曇時々雨",
        "height": 31
      }
    }
  ],
  "location": {
    "city": "大阪",
    "area": "近畿",
    "prefecture": "大阪府"
  },
  "publicTime": "2020-03-28T05:00:00+0900",
  "copyright": {
    "provider": [
      {
        "link": "http://tenki.jp/",
        "name": "日本気象協会"
      }
    ],
    "link": "http://weather.livedoor.com/",
    "title": "(C) LINE Corporation",
    "image": {
      "width": 118,
      "link": "http://weather.livedoor.com/",
      "url": "http://weather.livedoor.com/img/cmn/livedoor.gif",
      "title": "livedoor 天気情報",
      "height": 26
    }
  },
  "title": "大阪府 大阪 の天気",
  "description": {
    "text": " 大阪府は、前線や湿った空気の影響で雨となっています。\n\n 28日の大阪府は、前線や湿った空気の影響で雨となり、朝から昼過ぎまでは曇るでしょう。\n\n 29日の大阪府は、前線や湿った空気の影響でおおむね曇り、明け方まで雨が降る見込みです。\n\n【近畿地方】\n 近畿地方は、前線や湿った空気の影響で曇り、雨の降っている所があります。\n\n 28日の近畿地方は、前線や湿った空気の影響で曇り、夕方から雨が降るでしょう。\n\n 29日の近畿地方は、前線や湿った空気の影響でおおむね曇り、朝まで雨が降る見込みです。",
    "publicTime": "2020-03-28T04:47:00+0900"
  }
}

data class は以下のようになり、WeatherPropertyに詰めてやりとりを行うとし、それぞれのdata classは独立させてます。

data class WeatherProperty(
    val copyright: Copyright,
    val description: Description,
    val forecasts: Forecast,
    val link: String,
    val location: Location,
    val pinpointLocations: PinpointLocation,
    val publicTime: String,
    val title: String
)

data class Copyright(
    val provider: Provider,
    val link: String,
    val title: String,
    val image: Image
)

data class Provider(
        val providerlist: List<ProviderList>
)

data class ProviderList(
        val link: String,
        val name: String
)

data class Description(
        val publicTime: String,
        val text: String
)

data class Forecast(
        val forecastList: List<ForecastList>
)

data class ForecastList(
        val date: String,
        val dateLabel: String,
        val image: ImageX,
        val telop: String,
        val temperature: Temperature
)

data class ImageX(
        val height: Int,
        val title: String,
        val url: String,
        val width: Int
)

data class Temperature(
        val max: Max,
        val min: Any
)

data class Location(
        val area: String,
        val city: String,
        val prefecture: String
)

data class PinpointLocation(
        val linkName: List<LinkName>
)

data class LinkName(
        val link: String,
        val name: String
)

取得してきたJSONオブジェクトを変換するAPIは以下のようにしています。

private const val BASE_URL = "http://weather.livedoor.com/forecast/webservice/json/"


private val moshi = Moshi.Builder()
        .add(KotlinJsonAdapterFactory())
        .build()

//retrofitオブジェクトをMoshi使ってMoshiオブジェクトに変換
private val retrofit = Retrofit.Builder()
        .addConverterFactory(MoshiConverterFactory.create(moshi))
        .addCallAdapterFactory(CoroutineCallAdapterFactory())
        .baseUrl(BASE_URL)
        .build()

interface WeatherApiService {
    @GET("v1?city=270000")
    fun getProperties():
            Deferred<List<WeatherProperty>>
}

object WeatherApi {
    val retrofitService : WeatherApiService by lazy {
        retrofit.create(WeatherApiService::class.java)
    }
}

以上よろしくお願いします。

Comments

[hoshi-takanori]

WeatherProperty の pinpointLocations と forecasts と、Copyright の provider は配列なので、List か何かにしないといけないのでは。

[negoto]

すみません、JSONの見方がまだよくわかってないのですが、
pinponitLocations、forecasts、Copyrightのproviderのそれぞれの中身が配列になっていて、pinpointoLocations、forecasts、providerは配列になっていないと思いますが認識違いでしょうか？

[hoshi-takanori]

あ、ちゃんと見てませんでした。たぶん、質問文のクラス構造だと
{
　"pinpointLocations": {
　　"linkName": [
　　　{
　　　　"link": "http://weather.livedoor.com/area/forecast/2710000",
　　　　"name": "大阪市"
　　　},
という JSON になると思います。つまり、PinpointLocation, Forecast, Provider というクラスは不要だと思います。

[negoto]

すみません、そうするとどういうdata classになるか教えてもらえますか？
まだよくわかりません。

Answer 1

PinpointLocation, Forecast, Provider は削除して、以下の修正で動くと思います。

data class WeatherProperty(
    val copyright: Copyright,
    val description: Description,
    val forecasts: List<ForecastList>, // List に変更
    val link: String,
    val location: Location,
    val pinpointLocations: List<LinkName>, // List に変更
    val publicTime: String,
    val title: String
)

data class Copyright(
    val provider: List<ProviderList>, // List に変更
    val link: String,
    val title: String,
    val image: ImageX // クラス名修正
)

data class Temperature(
    val max: Max,
    val min: Any? // null があるので ? を追加 (Max? でもいいような)
)

interface WeatherApiService {
    @GET("v1?city=270000")
    fun getProperties():
            Deferred<WeatherProperty> // たぶんこれは List じゃないはず
}

あと、開発やデバッグのコツですが、JSON パーザーは余分なものは無視するので、いきなり全部のデータを定義するのではなく、まず次のような最低限のデータを定義して、少しずつ追加していけばいいと思います。

data class WeatherProperty (
    val description: Description,
    val title: String
)

Comments

[negoto]

やっぱりできませんでした。。。
アドバイスしてくれたように最低限のでやってみてもダメでした。

基本的なJSONで練習してみます。
回答ありがとうございました。