java - 使用 Retrofit 时，当回复有时是对象有时是数组时，如何解析 JSON 回复？

Question

我正在使用 Retrofit 来获取 JSON 回复。

这是我的实现的一部分 -

@GET("/api/report/list")
Observable<Bills> listBill(@Query("employee_id") String employeeID);

Bills 类是 -

public static class Bills {
    @SerializedName("report")
    public ArrayList<BillItem> billItems;
}

BillItem类如下 -

public static class BillItem {
    @SerializedName("id")
    Integer entryID;
    @SerializedName("employee_id")
    Integer employeeDBID;
    @SerializedName("type")
    String type;
    @SerializedName("subtype")
    String subtype;
    @SerializedName("date")
    String date;
    @SerializedName("to")
    String to;
    @SerializedName("from")
    String from;
    @SerializedName("amount")
    Double amount;
    @SerializedName("location")
    String location;
    @SerializedName("remark")
    String remark;
    @SerializedName("ispaid")
    String isPaid;
    @SerializedName("created_at")
    String createdAt;
    @SerializedName("updated_at")
    String updateAt;
}

问题是有时 REST API 返回 BillItem 的数组对象，但有时它只是一个 key-value一对。遇到这种情况该如何处理？

收到此响应后，一切正常，因为 JSONArray被映射到ArrayList<BillItem> -

{
   "emp":{
      "id":41,
      "name":"",
      "email":"",
      "created_at":"2016-02-01 10:36:38",
      "updated_at":"2016-02-01 10:36:38"
   },
   "report":[
      {
     "id":175,
     "employee_id":41,
     "type":"Travel",
     "subtype":"Car",
     "date":"2016-02-02 00:00:00",
     "to":"gaha",
     "from":"hshsj",
     "amount":"64",
     "location":"",
     "remark":"shhs",
     "ispaid":false,
     "created_at":"2016-02-01 13:52:52",
     "updated_at":"2016-02-01 13:52:52"
      },
      {
     "id":179,
     "employee_id":41,
     "type":"Travel",
     "subtype":"Car",
     "date":"2016-02-01 00:00:00",
     "to":"Gsh",
     "from":"Dgdh",
     "amount":"7646",
     "location":"",
     "remark":"Shsh",
     "ispaid":false,
     "created_at":"2016-02-01 14:39:48",
     "updated_at":"2016-02-01 14:39:48"
      }
   ]
}

但是，有时响应是这样的，它给出 JsonSyntaxException -

{
   "emp":{
      "id":41,
      "name":"",
      "email":"",
      "created_at":"2016-02-01 10:36:38",
      "updated_at":"2016-02-01 10:36:38"
   },
   "report":{
      "1":{
     "id":175,
     "employee_id":41,
     "type":"Travel",
     "subtype":"Car",
     "date":"2016-02-02 00:00:00",
     "to":"gaha",
     "from":"hshsj",
     "amount":"64",
     "location":"",
     "remark":"shhs",
     "ispaid":false,
     "created_at":"2016-02-01 13:52:52",
     "updated_at":"2016-02-01 13:52:52"
      },
      "2":{
     "id":179,
     "employee_id":41,
     "type":"Travel",
     "subtype":"Car",":"2016-02-01 00:00:00",
     "to":"Gsh",
     "from":"Dgdh",
     "amount":"7646",
     "location":"",
     "remark":"Shsh",
     "ispaid":false,
     "created_at":"2016-02-01 14:39:48",
     "updated_at":"2016-02-01 14:39:48"
      },
      "0":{
     "id":181,
     "employee_id":41,
     "type":"Travel",
     "subtype":"Car",
     "date":"2016-02-01 00:00:00",
     "to":"ggg",
     "from":"vg",
     "amount":"0",
     "location":"",
     "remark":"cvv",
     "ispaid":false,
     "created_at":"2016-02-01 17:43:43",
     "updated_at":"2016-02-01 17:43:43"
      },
      "3":{
     "id":182,
     "employee_id":41,
     "type":"Travel",
     "subtype":"Car",
     "date":"2016-02-01 00:00:00",
     "to":"Haha",
     "from":"Ahah",
     "amount":"0",
     "location":"",
     "remark":"Ahah",
     "ispaid":false,
     "created_at":"2016-02-01 17:53:58",
     "updated_at":"2016-02-01 17:53:58"
      }
   }
}

如何处理这样的回复？

Answer 1

当您使用 Gson 反序列化器时，您可以检查 JsonElement 中的类型:

Gson gson = new GsonBuilder()
            .registerTypeAdapter(BillItem.class, new BillItemDeserializer())
            .registerTypeAdapter(Bills.class, new BillsDeserializer())
            .create();

RestAdapter.Builder builder = new RestAdapter.Builder()
            //...
            .setConverter(new GsonConverter(gson));

public class BillsDeserializer implements JsonDeserializer<StringList> {

    public Bills deserialize(JsonElement json, Type typeOfT,
            JsonDeserializationContext context) throws JsonParseException {
         BillItemList value = new BillItemList();
         if (json.isJsonArray()) {
             for (JsonElement element : json.getAsJsonArray()) {
                 value.add(gson.fromJson(element, BillItem.class));
             }
         } else {
             value.add(gson.fromJson(element, BillItem.class));
         }
         return value;
     }
}

参见示例:Gson deserialization - Trying to parse a JSON to an Object