How to parse a JSON with dynamic “key” in android by using GSON

Question

I have been using GSON library to parse all the json string and get a JSON object. But now I need to parse is like this:

{
   "status":1,
   "info":[
      {
         "\u5a31\u4e50":"\u51b7\u76d8,\u9ad8\u811a\u676f,\u6211\u7684\u7cd6\u679c\u5c4b,\u670d\u52a1\u4e1a\u6d88\u8d39\u52b5"
      },
      {
         "\u7f8e\u5986":"\u4e2a\u62a4|\u5316\u5986#\u9762\u90e8\u62a4\u7406,\u4e2a\u4eba\u536b\u751f,\u8eab\u4f53\u62a4\u7406,\u9999\u6c34\u9999\u6c1b,\u6c90\u6d74|\u7f8e\u53d1\u7528\u54c1,\u5f69\u5986,\u7cbe\u6cb9SPA,\u773c\u90e8\u62a4\u7406,\u78e8\u7802\u53bb"
      },
      {
         "\u8863\u670d":"\u670d|\u9970|\u978b|\u5e3d#\u670d\u88c5,\u978b\u9774,\u5185\u8863,\u914d\u9970,\u536b\u8863,\u4f11\u95f2\u88e4,T\u6064,\u88d9\u5b50,\u886c\u886b,\u9488\u7ec7\u886b,\u5a74\u5e7c\u513f\u670d\u9970"
      }
   ],
   "total":3
}

The key fields are dynamic, so I don't know how to write a model class to read this.

Answer 1

How would you like your model class to look?

status and total would probably be int, so that only leaves info.

As an experiment, just add a field Object info and see how Gson would set it to an ArrayList<LinkedHashMap<String, String>> -- ugly and hard to access by key, but all the data is there. Given that information, the fastest way to model a class would be:

class Something {
  int status;
  List<Map<String, String> info;
  int total;
}

If you have control over how that JSON is generated, I suggest changing the structure of info from an array of objects [{a:b},{c:d},{e:f}] to just an object {a:b,c:d,e:f}. With this, you could just map it to a Map<String, String> with all the benefits like access by key, keys() and values():

class Something {
  int status;
  Map<String, String> info;
  int total;
}

If you want the latter model class without changing the JSON format, you'll have to write a TypeAdapter (or JsonDeserializer if you're only interested in parsing JSON, not generating it from your model class).

Here's a JsonDeserializer hat would map your original info JSON property to a plain Map<String, String>.

class ArrayOfObjectsToMapDeserializer
    implements JsonDeserializer<Map<String, String>> {

  public Map<String, String> deserialize(JsonElement json, Type typeOfT,
      JsonDeserializationContext context) throws JsonParseException {
    Map<String, String> result = new HashMap<String, String>();

    JsonArray array = json.getAsJsonArray();
    for (JsonElement element : array) {
      JsonObject object = element.getAsJsonObject();
      // This does not check if the objects only have one property, so JSON
      // like [{a:b,c:d}{e:f}] will become a Map like {a:b,c:d,e:f} as well.
      for (Entry<String, JsonElement> entry : object.entrySet()) {
        String key = entry.getKey();
        String value = entry.getValue().getAsString();
        result.put(key, value);
      }
    }
    return result;
  }
}

You need to register this custom JsonDeserializer similar to this:

GsonBuilder builder = new GsonBuilder();
builder.registerTypeAdapter(
    new TypeToken<Map<String, String>>() {}.getType(),
    new ArrayOfObjectsToMapDeserializer());
Gson gson = builder.create();

Note that this registers the custom deserializer for any Map<String, String> regardless in what class it is encountered. If you don't want this, you'll need to create a custom TypeAdapterFactory as well and check the declaring class before returning and instance of the deserializer.

Answer 2

Here goes a solution, which does not requires to make a JsonDeserializer.

All you can create is a JsonElement in a map Map.Entry<String, JsonElement>and use a for loop to iterate over the entries

//parsing string response to json object
JsonObject jsonObject = (JsonObject) new JsonParser().parse(jsonString);
//getting root object
JsonObject dateWiseContent = jsonObject.get("rootObject").getAsJsonObject();
    
for (Map.Entry<String, JsonElement> entry : dateWiseContent.entrySet()) {      
    //this gets the dynamic keys
    String  dateKey = entry.getKey();
            
    //you can get any thing now json element,array,object according to json.
            
    JsonArray jsonArrayDates = entry.getValue().getAsJsonArray();
}

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