Deserialize enum ignoring case in Spring Boot controller

Question

I have Spring Boot endpoint which has enum as query param:

@GetMapping("/example")
public List<Example> getByEnum(@RequestParam(name = "exampleEnum", required = false) ExampleEnum exampleEnum) {
    // code
}

And enum class:

public enum ExampleEnum {
    FIRST,
    SECOND,
}

If I pass uppercase enum value to the endpoit, it deserializes well but it throws error for lowercase:

java.lang.IllegalArgumentException: No enum constant 

How to deserialize enum ignoring case in Spring Boot Rest endpoint?

This question is not duplicate because it's related to query param deserialization.

Answer 1

EDIT: The answer below is incorrect. You have to define a custom PropertyEditor and register it with Spring @InitBinder which I explained in this post. Thanks to @Dave for pointing this out in the comments.

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Spring Boot 2.0 is using Jackson 2.9 which has ACCEPT_CASE_INSENSITIVE_ENUMS feature. You should be able to enable it by setting

spring.jackson.mapper.ACCEPT_CASE_INSENSITIVE_ENUMS = true 

property as per docs, Appendix A.