How to get the @RequestBody in an @ExceptionHandler (Spring REST)

You can reference the request body object to a request-scoped bean. And then inject that request-scoped bean in your exception handler to retrieve the request body (or other request-context beans that you wish to reference).

// @Component
// @Scope("request")
@ManagedBean
@RequestScope
public class RequestContext {
    // fields, getters, and setters for request-scoped beans
}

@RestController
@RequestMapping("/api/v1/persons")
public class PersonController {

    @Inject
    private RequestContext requestContext;

    @Inject
    private PersonService personService;

    @PostMapping
    public Person savePerson(@RequestBody Person person) throws PersonServiceException {
         requestContext.setRequestBody(person);
         return personService.save(person);
    }

}

@ControllerAdvice
public class ExceptionMapper {

    @Inject
    private RequestContext requestContext;

    @ExceptionHandler(PersonServiceException.class)
    protected ResponseEntity<?> onPersonServiceException(PersonServiceException exception) {
         Object requestBody = requestContext.getRequestBody();
         // ...
         return responseEntity;
    }
}