Spring Boot RestController, On Error Status Response Body, Message of Error is empty

On my Spring Boot RestController I want to pass a custom error message to the response body by throwing a custom exception. I was following the guide on https://dzone.com/articles/spring-rest-service-exception-handling-1

These are my code Snippets:

UserNotFoundException

import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.ResponseStatus;


@ResponseStatus(HttpStatus.NOT_FOUND)
public class UserNotFoundException extends RuntimeException {
    public UserNotFoundException(String message) {
        super(message);
    }
}

The simplified RestController

@RestController
public class CreateRfqController {

    @PostMapping("api/create-rfq")
    public ResponseEntity<Rfq> newRfq(@RequestBody Rfq newRfq) {
        throw new UserNotFoundException("User Not Found");
    }
}

When calling my Rest API I always get an empty message:

{
    "timestamp": "2020-06-24T18:23:30.846+00:00",
    "status": 404,
    "error": "Not Found",
    "message": "",
    "path": "/api/create-rfq"
}

instead i want "message": "User Not Found",

At one Stage I even had it working. Seems like i messed up on some Point.

In the log you can even see the User Not Found text and the correct Exception Class

24 Jun 2020;20:50:52.998 DEBUG = 145: o.s.w.s.m.a.ResponseStatusExceptionResolver - Resolved [configRestServer.exceptions.UserNotFoundException: User Not Found]
24 Jun 2020;20:50:52.998 DEBUG = 1131: o.s.w.s.DispatcherServlet - Completed 404 NOT_FOUND
24 Jun 2020;20:50:53.003 DEBUG = 91: o.s.w.s.DispatcherServlet - "ERROR" dispatch for POST "/error", parameters={}
24 Jun 2020;20:50:53.006 DEBUG = 414: o.s.w.s.m.m.a.RequestMappingHandlerMapping - Mapped to org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController#error(HttpServletRequest)
24 Jun 2020;20:50:53.018 DEBUG = 265: o.s.w.s.m.m.a.HttpEntityMethodProcessor - Using 'application/json', given [*/*] and supported [application/json, application/*+json, application/json, application/*+json]
24 Jun 2020;20:50:53.018 DEBUG = 91: o.s.w.s.m.m.a.HttpEntityMethodProcessor - Writing [{timestamp=Wed Jun 24 20:50:53 CEST 2020, status=404, error=Not Found, message=, path=/api/create-rf (truncated)...]
24 Jun 2020;20:50:53.038 DEBUG = 1127: o.s.w.s.DispatcherServlet - Exiting from "ERROR" dispatch, status 404

my build.gradle

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-web'
    testImplementation('org.springframework.boot:spring-boot-starter-test') {
        exclude group: 'org.junit.vintage', module: 'junit-vintage-engine'
    }

// https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-jdbc
    compile group: 'org.springframework.boot', name: 'spring-boot-starter-jdbc', version: '2.3.0.RELEASE'

// https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-security
    compile group: 'org.springframework.boot', name: 'spring-boot-starter-security', version: '2.3.1.RELEASE'

compile group: 'org.apache.commons', name: 'commons-lang3', version: '3.9'

    runtime group: 'com.oracle', name: 'ojdbc6', version: '11.2.0.3'

    compile group: 'com.sun.mail', name: 'javax.mail', version: '1.6.2'

// https://mvnrepository.com/artifact/org.apache.httpcomponents/httpclient
    compile group: 'org.apache.httpcomponents', name: 'httpclient', version: '4.5.12'

Update: On Purpose I passed some wrong variable type into my RFQ Object to produce a default error. Even here in the response, the message is empty:

{
    "timestamp": "2020-06-24T19:20:18.831+00:00",
    "status": 403,
    "error": "Forbidden",
    "message": "",
    "path": "/api/create-rfq"
}

It is changed behavior in Spring Boot 2.3.0. Change the property server.error.include-message = always in your application.properties/yml file.

More informations: Changes to the Default Error Page’s Content and Spring Boot server properties