Weird! Long value round off issue in spring boot

user_1449101 0
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When I try to serialize an object to JSON using Jackson object mapper, it works perfectly.

 {"id":1291741231928705024,"uuid":null,"email":"kannanrbk.r@gmail.com"}

Whereas, when I try to access it using spring rest controller. The long value numbers are rounded off, the last 3 digits.

enter image description here

I read existing questions in the stackoverflow, most of them suggest changing the datatype to string. But we used the Long value reference in most of the places, changing datatype will need some refactoring.

I did my initial analysis:

  1. We are using Jackson ObjectMapper
  2. From Spring, it indirectly calls MappingJackson2HttpMessageConverter
  3. This problem might be somewhere around the JSONParser, where it treats any number as a double (15 digits) and after that, it's rounded off

Is there any way to fix this issue?

spring-boot jackson spring java
2 Answers

Is there any way to fix this issue?

There is no problem with Jackson/Java/Spring Boot, but with JavaScript/Browser.

Trying to reproduce the issue I serialized the same object and got this using curl:

$ curl localhost:8080
{"id":1291741231928705024,"uuid":null,"email":"kannanrbk.r@gmail.com"}

Here the number is correctly serialized.

The same json viewed in Firefox does truncate:

Truncated value in Firefox (JSON tab)

However the "Raw Data" tab displays the number correctly:

Correct value displayed in Firefox ("Raw Data tab").

In JavaScript 1291741231928705024 is not safe integer (see Number.isSafeInteger()):

Number.isSafeInteger(1291741231928705024);
false

The number is greater than 2^53 - 1 so it gets rounded. Even more confusing situations are possible in JavaScript:

> 1291741231928705024 === 1291741231928705022
true

Possible solution

First of all check your client against this kind of problems. If it can safely deserialize such numbers then you're safe.

Or you can serialize longs as Strings (as you mentioned in the question), this is what Twitter proposes in its Twitter IDs (snowflake) article:

To allow Javascript and JSON parsers to read the IDs, Twitter objects include a string version of any ID when responding with JSON. Status, User, Direct Message, Saved Search and other IDs in the Twitter API are therefore returned as both an integer and a string in JSON responses.

user_64866220

Try with bigInt for your primary key

user_71218960
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