Java: org.json.JSONObject - creating a new instance removes trailing zeros from big decimals

Question

Take for example this short JSON taken as a String from an API response using RestAssured:

{
    "id": "4d27afb18bfa4eb5917beee9aaddfa76",
    "hedgeId": 205598,
    "sellCurrency": "USD",
    "buyCurrency": "EUR",
    "buyAmount": 473935.00,
    "sellAmount": 585538.30,
}

Whenever I do JSONObject foo = new JSONObject(thatStringAbove);, this instance is created:

{
  "hedgeId": 205598,
  "buyAmount": 473935,
  "sellAmount": 585538.3,
  "id": "4d27afb18bfa4eb5917beee9aaddfa76",
  "sellCurrency": "USD",
  "buyCurrency": "EUR"
}

Notice the trailing zeros from amount nodes are stripped. This looks like a bug to me but does anyone know of a workaround / solution how to prevent this from happening?

Few notes:

I'd like to solve this using same library (org.json)

If at all possible, I'd like to construct the instance from a string like how I'm doing it currently

Maven dependency:

        <dependency>
            <groupId>org.json</groupId>
            <artifactId>json</artifactId>
            <version>20170516</version>
        </dependency>

Appreciate the help!

You're serializing to a JSON `number` type, which is always floating-point and doesn't have a precision. If you want it to keep the formatting, you'll need to use a string. — chrylis -cautiouslyoptimistic-, Apr 04 '18 at 03:38

teppic · Accepted Answer · 2018-04-04T03:53:26.893

You won't be able to do this with the org.json library. It deliberately strips trailing zeros during serialisation.

From the relevant method JSONObject.numberToString():

public static String numberToString(Number number) throws JSONException {
    if (number == null) {
        throw new JSONException("Null pointer");
    }
    testValidity(number);

    // Shave off trailing zeros and decimal point, if possible.

    String string = number.toString();
    if (string.indexOf('.') > 0 && string.indexOf('e') < 0
            && string.indexOf('E') < 0) {
        while (string.endsWith("0")) {
            string = string.substring(0, string.length() - 1);
        }
        if (string.endsWith(".")) {
            string = string.substring(0, string.length() - 1);
        }
    }
    return string;
}

I'd suggest using a more customisable library like jackson or gson.

Gson will respect the scale on the number, allowing you to perform your round trip without losing trailing zeros:

Gson gson = new GsonBuilder().setPrettyPrinting().create();
JsonObject jsonObject = gson.fromJson(in, JsonObject.class);
System.out.println(gson.toJson(jsonObject));

Output:

{
    "id": "4d27afb18bfa4eb5917beee9aaddfa76",
    "hedgeId": 205598,
    "sellCurrency": "USD",
    "buyCurrency": "EUR",
    "buyAmount": 473935.00,
    "sellAmount": 585538.30
}

It will also do mapping to Objects if you desire.

Thanks for this info. Wish I had opted for gson earlier. Using it now would require some work and time. Will wait for other answers and will accept this if nothing else comes. — iamkenos, Apr 04 '18 at 04:20

score 0 · Answer 2 · answered Apr 04 '18 at 03:41

0

One Way is To Use String Instead of Number e.g

{
"buyAmount": "473935.00",
"sellAmount":"585538.30",
}

If You are Using BigDecimal Use toPlainString method to avoid removing trailing Zeros

answered Apr 04 '18 at 03:41

Muhammad Waqas

367
3
13

Unfortunately I can't modify the spec. The data will be coming from an API response which is already defined. – iamkenos Apr 04 '18 at 04:14

Java: org.json.JSONObject - creating a new instance removes trailing zeros from big decimals

2 Answers2