Question

Have an array, when the size is 1, the json data I received does NOT contains []; like

{"firstname":"tom"}

when the size is larger than 1, the data I received contains [], like

[{"firstname":"tom"},{"firstname":"robert"}]

Currently my class contains an array property

String[] firstname;
//getter setter omit here

Code to handle this likes

ObjectMapper mapper = new ObjectMapper();    
MyClass object = mapper.readValue(json, MyClass.class);

When the size is larger than 1, the deserialization works. However when size is 1, the deserialization failed.

I am currently using jackson, any solution for this problem?

I am wondering if jackson/gson or any other library can handle this?

Answer 1

For Jackson specifically, your best bet would to first bind to a JsonNode or Object, like:

Object raw = objectMapper.readValue(json, Object.class); // becomes Map, List, String etc

and then check what you got, bind again:

MyClass[] result;
if (raw instanceof List<?>) { // array
  result = objectMapper.convertValue(raw, MyClass[].class);
} else { // single object
  result = objectMapper.convertValue(raw, MyClass.class);
}

But I think JSON you are getting is bad — why would you return an object, or array, intead of just array of size 1? — so if at all possible, I’d rather fix JSON first. But if that is not possible, this would work.