How to handle a NumberFormatException with Gson in deserialization a JSON response

How to handle a NumberFormatException with Gson in deserialization a JSON response

When deserializing a JSON response using Gson, you can handle a NumberFormatException if the JSON data doesn't match the expected numeric format. Gson provides a mechanism to specify custom deserialization logic using custom deserializer classes or annotations. You can use this to catch and handle exceptions during deserialization.

Here's how you can handle a NumberFormatException during JSON deserialization using Gson:

  • Create a custom deserializer class that implements the JsonDeserializer interface. In the deserialize method, you can parse the JSON value as a number and handle any NumberFormatException that may occur.
import com.google.gson.JsonDeserializer; import com.google.gson.JsonElement; import com.google.gson.JsonDeserializationContext; import com.google.gson.JsonParseException; public class MyNumberDeserializer implements JsonDeserializer<Number> { @Override public Number deserialize(JsonElement json, java.lang.reflect.Type typeOfT, JsonDeserializationContext context) throws JsonParseException { try { return json.getAsNumber(); } catch (NumberFormatException e) { // Handle the NumberFormatException here or throw a custom exception throw new JsonParseException("Invalid number format: " + json.getAsString(), e); } } }
  • Register the custom deserializer with your Gson instance:
import com.google.gson.Gson; import com.google.gson.GsonBuilder; public class MyJsonDeserializer { public static void main(String[] args) { Gson gson = new GsonBuilder() .registerTypeAdapter(Number.class, new MyNumberDeserializer()) .create(); String json = "{\"value\": \"42\"}"; // Example JSON data with a string value MyObject myObject = gson.fromJson(json, MyObject.class); } }

In this example, we've registered the MyNumberDeserializer as a custom deserializer for the Number type. When Gson encounters a JSON value that's supposed to be a number but is in an invalid format (e.g., a string that cannot be parsed as a number), the custom deserializer will catch the NumberFormatException and throw a JsonParseException with a more informative error message.

You can adjust the error handling and exception propagation logic in the custom deserializer based on your specific requirements.

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