[Bug]: Example value starting with a number is parsed incorrectly

[Sagr-gupta]

Description

When an example in an OpenAPI annotation (e.g., @Schema(example = "5 lacs per annum")) starts with a number, it appears that Swagger Core interprets the value as a numeric literal because the example begins with a digit. This results in the example being serialized as a number instead of a string.

For instance :

@Schema(example = "5 lacs per annum") private String salary;

In the generated OpenAPI schema, the example becomes:

"example": 5

instead of :

"example": "5 lacs per annum"

Where the issue occurs

The issue originates from the following code in io.swagger.v3.core.util.AnnotationsUtils#getSchemaFromAnnotation:

Because Json31.mapper().readTree(...) interprets any string starting with a digit as JSON numeric content, the portion "lacs per annum" is ignored and only the number 5 is retained.

Affected Version

swagger-core-jakarta: 2.2.36

springdoc-openapi: 2.8.13

For reproducing the issue below I have attached a demo project. Kindly take reference.

openapi.zip

[zero2top]

Hi! 👋 I'd like to work on this issue if it's not already being handled. It seems the problem comes from AnnotationsUtils#getSchemaFromAnnotation, where Json31.mapper().readTree(...) parses a numeric string as a number.

I plan to:

• Add a conditional check to treat examples starting with a digit as strings.
• Add a test case in AnnotationsUtilsTest to verify this behavior.

Please let me know if it's okay for me to proceed. Thanks!

[daniel-kmiecik]

@zero2top We encourage you to prepare a fix for this issue. Once you have a pull request ready, we will review it and work with you on any feedback and final merge.

Thanks for your contribution!

[zero2top]

Hi! 👋

I’ve completed the fix for this issue.

✔️ What I changed

• Updated AnnotationsUtils#getSchemaFromAnnotation to ensure example values starting with digits are always treated as strings.
• Added a test case testExampleStartingWithNumberShouldBeString in AnnotationsUtilsTest to validate this behavior.

📌 Status

The fix is implemented and tested locally — I’m preparing the pull request now.

Thanks!