无法在 Kotlin 中使用带有 Gson 的 TypeToken + 泛型处理 json 树列表

Question

我得到的json结构如下：

{
  "object": "list",
  "total": 3,
  "data": [
    {
      "object": "brand",
      "id": "15243937043340",
      "company": {
        "object": "company",
        "id": "956936000",
        "name": "ABC"
      },
      "name": "Kindle",
      "images": [
        "http://www.spacecentrestorage.com/assets/uploads/General/SCS-Slide02-Commercial.jpg"
      ]
    },
    {
      "object": "brand",
      "id": "15243937043340",
      "company": {
        "object": "company",
        "id": "956936000",
        "name": "ABC"
      },
      "name": "Kindle",
      "images": [
        "http://www.spacecentrestorage.com/assets/uploads/General/SCS-Slide02-Commercial.jpg"
      ]
    },
    {
     "object": "brand",
      "id": "15243937043340",
      "company": {
        "object": "company",
        "id": "956936000",
        "name": "ABC"
      },
      "name": "Kindle",
      "images": [
        "http://www.spacecentrestorage.com/assets/uploads/General/SCS-Slide02-Commercial.jpg"
      ]
    }
  ],
  "associated": {}
}

这是我的 Gson 数据类映射：

data class Response (

        @SerializedName("object")
        val obj: String,
         val total: Int,
         val data: List<*>,
         val associated: Response
)


data class Brand (

        @SerializedName("object")
        val obj: String,
        val id: String,
         val name: String,
         val images: List<String>,
         val company: Company
)

   data class Company (

        @SerializedName("object")
        val obj: String,
        val id: String,
         val name: String 
)

在上面提取树时，我发现返回的数据字符串变成 Malformed Json 并在 $[0].companies.null 上给出 MalformedJsonException

我已阅读有关 recursive deserialisation function 的信息，但它不适用于我的情况。我采用如下反序列化方法，使用原始方法，它会导致错误

  val response = gson.fromJson(queryResult , Response::class.java)
        println("result 2 : $response" )
        val dataString = response.data.toString()
        println("result 3 : $dataString" )
        val brands  = Gson().fromJson(dataString, Array<Brand>::class.java).toMutableList()
        println("result 4 : $brands" )

我想问一下：

1. 如果将json组件返回到字符串，是否所有的缩进和符号“都被删除？

2. 要提取对象列表元素的所有关联对象，使用 Gson 反序列化对象列表需要采取哪些预防措施？

Answer 1

如果将Response中data列表的类型参数设置为Brand，GSON就知道如何反序列化列表中的项目了。

data class Response (

    @SerializedName("object")
    val obj: String,
    val total: Int,
    val data: List<Brand>, 
    val associated: Response

)

使用这个不需要再次解析列表中的项目，你可以像这样得到所有brands：

val response = Gson().fromJson(queryResult , Response::class.java)
val dataList = response.data
print("brands: " )
dataList.forEach { println(it) }