Parse JSON uint32/uint64 numbers in Java

Question

I want to parse some JSON data in uint32 and uint64 format that are sent as numbers (without quotes), and then use them in java.

I found out that I can store them as unsigned integers via the parseUnsignedInt(String) method, but the problem is that I cannot get the json value as a string, because it's lacking quotes. If I parse it as an int, the value returned is wrong before I have the chance to convert it.

Example:

// data is a JSONObject containing: {"number" : 4294967294}
...
System.out.println(data.getInt("number"));
// returns: -10001
System.out.println(Integer.parseUnsignedInt(data.getString("number")));
// returns: JSONObject["number"] not a string.
System.out.println(Integer.parseUnsignedInt(Integer.toString(data.getInt("number"))));
// returns: Illegal leading minus sign on unsigned string -10001.

Is there a way to extract the value from the json object as a string (or any other way that doesn't ruin it)?

Depends on the library you are using for parsing, It looks like the interger is overflowing. Have you tried parsing it as Long ? — Althaf M, Mar 23 '20 at 14:26
Integer max value :2147483647 < ( 4294967294 ) Long max value :9223372036854775807 — Althaf M, Mar 23 '20 at 14:27
@AlthafM That's the problem they are facing. How would you get the number directly as a long? — cegredev, Mar 23 '20 at 14:29
I thought about that option, but I also need to handle uint32 with Long.parseUnsignedInt(String), so I'm searching for a universal solution, if any. // I also need to parse uint64 in the long run, but that's a different story, let's leave it for later :P — Yiorgos, Mar 23 '20 at 14:29
if you are using javax.json , then you can do data.getJsonNumber("number").longValue() — Althaf M, Mar 23 '20 at 14:41
data.getString("number") returns «JSONObject["number"] not a string». That's the core of my problem, that I cannot parse the value as a string in the first place. — Yiorgos, Mar 23 '20 at 14:41
@Yiorgos got a chance to test this : data.getJsonNumber("number").longValue() — Althaf M, Mar 23 '20 at 14:53
I actually tested the equivalent from org.json.JSONObject that I'm currently using: Integer.parseUnsignedInt(Long.toString(data.getLong("number"))) and it worked, but I'm still searching for a way to directly get the json values as string as stated in the question title, in order to be able to use it to parse uint64 as well. — Yiorgos, Mar 23 '20 at 15:04

score 1 · Answer 1 · answered Mar 23 '20 at 15:04

as far as I know, there is no way to read json-numbers as strings (as long as using standard libs).

But I think, finally, you want to handle numbers, so, converting them into string is maybe inconvenient.

Instead, you can read as json-number and then handle numbers instead of strings:

final JsonNumber jsonNumber = data.getJsonNumber("number");
System.out.println(jsonNumber.longValue());
// returns: 4294967294

From here on you can convert it into uint32 as you like.

Hope this helps.

samabcde · Accepted Answer · 2020-03-23T15:26:16.003

Suppose the library using is org.json. getLong method can not support uint64. We should use getBigInteger in such case.

import org.json.JSONObject;

public class JsonParseLargeInteger {
    public static void main(String[] args) {
        String uint32MaxValueJson = "{\"number\" : 4294967296}";
        JSONObject uint32MaxValueJsonObject = new JSONObject(uint32MaxValueJson);
        System.out.println(((Integer) uint32MaxValueJsonObject.getInt("number")).toString());
        // Result is 0
        System.out.println(((Long) uint32MaxValueJsonObject.getLong("number")).toString());
        // Result is 4294967296
        System.out.println(uint32MaxValueJsonObject.getBigInteger("number").toString());
        // Result is 4294967296

        String uint64MaxValueJson = "{\"number\" : 18446744073709551615}";
        JSONObject uint64MaxValueJsonObject = new JSONObject(uint64MaxValueJson);
        System.out.println(((Integer) uint64MaxValueJsonObject.getInt("number")).toString());
        // Result is -1
        System.out.println(((Long) uint64MaxValueJsonObject.getLong("number")).toString());
        // Result is -1
        System.out.println(uint64MaxValueJsonObject.getBigInteger("number").toString());
        // Result is 18446744073709551615
    }
}

Yes, I think BigInteger is what I was missing in order to elevate the solution to uint64 as well. I understand that this logic can be implemented with both org.json and javax.json. Any particular advantage any of those libraries has over the other? — Yiorgos, Mar 23 '20 at 15:23
It depends on your use case, JsonNumber (of javax) provide more general handling on number(can be `int`, `long`, `BigInteger` or `BigDecimal`). I suppose such generalization require trade off in performance. On the other hand, `org.json` provide specific function to handle different data type, which should be faster. So it depends on whether you know the type of number you are handling. — samabcde, Mar 23 '20 at 15:44

Parse JSON uint32/uint64 numbers in Java

2 Answers2