gson 处理null

1.定义null处理类

 class StringConverter : JsonSerializer<String?>,
     JsonDeserializer<String?> {
     override fun serialize(
         src: String?, typeOfSrc: Type?,
         context: JsonSerializationContext?
     ): JsonElement {
         return if (src == null) {
             JsonPrimitive("")
         } else {
             JsonPrimitive(src.toString())
         }
     }

     @Throws(JsonParseException::class)
     override fun deserialize(
         json: JsonElement, typeOfT: Type?,
         context: JsonDeserializationContext?
     ): String {
         return json.asJsonPrimitive.asString
     }
 }

2.修改构造gson方式

     fun parseDevices(array : JsonArray){
         val gson = GsonBuilder().run {
             registerTypeAdapter(String::class.java, StringConverter())
             create()
         }
         for (je in array){
             val obj = je.asJsonObject
             if(!obj.has("type")) continue
             val type = obj.get("type").asInt
             when(type){
                  -> {
                     val ward = gson.fromJson(je,Wardship::class.java)
                     ...
                 }

                 //...
             }
         }
     }