Gson: How do I parse polymorphic values that can be either lists or strings?

Question

I need to parse a JSON file that contains long list of customers. In the JSON file each customer may have one id as a string:

{
  \"cust_id\": \"87655\",
  ...
}         


        

Answer 1

You can just simply specify all values as array, even if is just one value.

{
  "cust_id": ["87655"],
  ...
},

UPDATE: If you cannot change the json, you can bind every field in Customer class except custId and set it manually.

public class Customer {
    private String[] custId;

    public String getCustId() {
        return custId;
    }

    public void setCustId(String custId) {
        custId = new String[] {custId};
    }

    public void setCustId(String[] custId) {
        this.custId = custId;
    }
}

And then parse manually:

Gson gson = new Gson();
Customers customers = gson.fromJson(json, Customers.class);
Object custId = new JSONObject(json).get("cust_id");
if (custId instanceof String) {
  customers.setCustId((String) custId);
else if (custId instanceof JSONArray) {
  customers.setCustId(convertToStringArray(new JSONArray(custId)));
}