Modify Json Payload Data Using Gson

Modifying via a POJO

User user = gson.fromJson(originalJson, User.class);
user.setAge(30);
String updatedJson = gson.toJson(user);

Modifying via JsonObject

JsonObject obj = JsonParser.parseString(originalJson).getAsJsonObject();
obj.addProperty("age", 30);
String updatedJson = obj.toString();

Why Testers Do This

Modifying a base payload dynamically lets a test create many variations (e.g., valid vs invalid data) from a single template file, without maintaining a separate JSON file for every scenario.