How to create a custom error message for a spring boot rest aplication

Question

I am using Spring Boot to handle REST calls. In this context, I have implemented a controller class with the following method:

@GetMapping("/{id}")
public ResponseEntity<employeeDetails> getEmployee(@PathVariable Long id) {
    Optional<Employee> employee = employeeService.getEmployee(id);
    if (employee.isPresent()) {
        return ResponseEntity.ok(employee.get());
    } else {
        throw new ApiRequestException("Could not find requested employee");
    }
}

I am now sending a request, asking for a non-existent employee. I have verified that the else-block is executed. My issue is that I am not returned a custom error message, instead I see the same old error message in my Browser console that I have seen before implementing the ApiRequestException:

I cannot understand why I don't see my custom error message. Here is how I have implemented the ApiRequestException:

1. I have implemented the ApiRequestException class:

    public class ApiRequestException extends RuntimeException { public ApiRequestException(String message) { super(message); } }

2. I have implemented an Exception handler:

    @ControllerAdvice public class ApiExceptionHandler { @ExceptionHandler(value = { ApiRequestException.class }) public ResponseEntity<Object> handleApiRequestException(ApiRequestException e) { HttpStatus badRequestStatus = HttpStatus.BAD_REQUEST; ApiRequestError apiRequestError = new ApiRequestError(badRequestStatus, e.getMessage()); return ResponseEntity.status(badRequestStatus).body(apiRequestError); } }

3. Well, as you can see, the exception handler is using an ApiRequestError class. I have implemented this as well: It's just a class that stores a message-string and an httpStatus.

When debugging my application, I have verified that the exception handler is called. Setting a breakpoint inside my GET-Controller shows that the ApiRequestException is thrown. The exception is handled by the ExceptionHandler.

So, anyways, I cannot explain why there is no custom error message in my browser console, but instead what seems to be a default message generated by Spring Boot. Can somebody help?

===================================================

update:

As it turns out, this issue seems to be related to my frontend, not my backend. The code I have presented here works fine. I have tested this by logging the error message in the way described in this follow-up question.

Answer 1

Try extending ResponseEntityExceptionHandler

@ControllerAdvice
public class ApiExceptionHandler extends ResponseEntityExceptionHandler{
    ...
}

Answer 2

Did you add these configs in the properties file?

server.error.include-message=always
server.error.include-binding-errors=always