Deserializing with Gson into different POJO types

Question

I have Websocket API, which spews out data in JSON format, and client endpoint reacts on them asynchronously. Since Jsons are lengthy, I want to work with them in deserialized form. Gson can deserialize JSON to POJO objects. But what to do, if different incoming JSONs have totally different structure?

For example, 2 channels respond in the following manner:

"symbols" channel

{
    "channel": "symbols",
    "action": "snapshot",
    "data": [
     {
       "symbol": "BTC_USDT",
       "baseCurrencyName": "BTC",
       "quoteCurrencyName": "USDT",
       "displayName": "BTC/USDT",
       "state": "NORMAL",
       "visibleStartTime": 1234567890,
       "tradableStartTime": 1234567890,
       "symbolTradeLimit": {
          "symbol": "BTC_USDT",
          "priceScale": 10,
          "quantityScale": 8,
          "amountScale": 8,
          "minQuantity": "0.000000000000000001",
          "minAmount": "0.000000000000000001",
          "highestBid": "0.00",
          "lowestAsk": "0.00"
       },
       "crossMargin": {
          "supportCrossMargin": true,
          "maxLeverage": 3
       }
     }
    ]
}

"book" channel

{
  "channel": "book",
  "data": [{
    "symbol": "BTC_USDT",
    "createTime": 1648052239156,
    "asks": [],
    "bids": [
      ["40001.5", "2.87"],
      ["39999.4", "1"]
    ],
    "id": 123456,
    "ts": 1648052239192
  }, 
  … 
  {
    "symbol": "BTC_USDT",
    "createTime": 1648052239156,
    "asks": [],
    "bids": [
      ["40001", "2.87"],
      ["39999", "1"]
    ],
    "id": 345678,
    "ts": 1648052239192
  }]
}

The most obvious way is trying to deserialize JSON into each POJO class and catch JsonSyntaxException when POJO class is not correct.

public void handleMessage(String message) {

   SymbolsResponse symbolsResponse;
   BookResponse bookResponse;

   try {
        bookResponse = gson.fromJson(message, BookResponse.class);
        if (bookResponse != null &&
            bookResponse.getChannel().equals("book") &&
            bookResponse.getData().get(0).getAsks().size() > 0) {

             // Here is handling logic for first message type

        }
   } catch (NullPointerException | JsonSyntaxException ignoredException) {
   }


   try {
        symbolsResponse = gson.fromJson(message, SymbolsResponse.class);
        if (symbolsResponse.getChannel().equals("symbols") &&
            symbolsResponse.getData() != null) {
                // Here is handling logic for second message type
        }
    } catch (NullPointerException | JsonSyntaxException ignoredException) {
    }
}

However, this looks somehow ugly and non-optimal.

Deserializing with Gson into different POJO types

0 Answers0