Java – JSON deserialization problem

There is an array. When the size is 1, the JSON data I receive does not contain []; like

{"firstname":"tom"}

When the size is greater than 1, the data I receive contains [], such as

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

Currently, my class contains an array property

String[] firstname;
//getter setter omit here

Code processing this like

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

Deserialization works when the size is greater than 1 However, when size is 1, deserialization fails

I am currently using Jackson, any solution to this problem?

I wonder if Jackson / gson or any other library can deal with this problem?

Solution

Especially Jackson, your best choice is to bind to jsonnode or object first, such as:

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

Then check what you get and 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 the JSON you get is terrible - why do you return an object or array with only array 1 So if possible, I'd rather fix JSON first But if this is not possible, it will work