This is a regression from spring boot 4.0.0-M3

Description

DemoApplication.java

I add custom properties to my ProblemDetail errors.

With the sample code attached, on 4.0.0-M3 I get this : 

{
  "detail": "Simulated error",
  "instance": "/hello",
  "properties": {
    "customProperty": "Custom Value"
  },
  "status": 400,
  "title": "OH NOOOOO :(",
  "type": null
}

expected result (from 4.0.0-M2)

{
  "title": "OH NOOOOO :(",
  "status": 400,
  "detail": "Simulated error",
  "instance": "/hello",
  "customProperty": "Custom Value"
}

As you can see there is a "properties" node which should not be there

My analysis

HttpMessageConvertersAutoConfiguration creates an HttpMessageConverters instance based on : 1. HttpMessageConverter from the context (additionalConverters) 2. default HttpMessageConverter list

In both cases there is a JacksonJsonHttpMessageConverter, as shown here:

Image \

The first one (from additionalConverters) takes precedence, and is created by JacksonHttpMessageConvertersConfiguration. It uses the JsonMapper created in JacksonAutoConfiguration using configuration properties (spring.jackson. ) It doesn't add support for ProblemDetailJacksonMixin.*

On the other hand, the 2nd JacksonJsonHttpMessageConverter created with default constructor adds ProblemDetailJacksonMixin

solution

Well, I'm not sure. Maybe JsonMixinModuleEntries should add the ProblemDetailJacksonMixin if it's found in classpath ? (or handle something with @ConditionalOnClass(ProblemDetailJacksonMixin.class) ?)

Comment From: wilkinsona

@bclozel could this be related to #46411, only appearing now due to Boot upgrading to Jackson 3 in 4.0.0-M3?