ErrorHandlerServlet.java

package org.flasby.security.servlet;

import java.io.PrintWriter;
import java.io.StringWriter;

import org.flasby.security.Auth403Exception;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;

@ControllerAdvice
class CustomControllerAdvice {
    @ExceptionHandler(Auth403Exception.class) // exception handled
    public String handleHttp403Exceptions( Exception e ) {
        // Simply use a standard error page for 403
        return "error";
    }

    // fallback method
    @ExceptionHandler(Exception.class) // exception handled
    public ResponseEntity<ErrorResponse> handleExceptions(
        Exception e
    ) {
        // ... potential custom logic

        HttpStatus status = HttpStatus.INTERNAL_SERVER_ERROR; // 500

    // converting the stack trace to String
    StringWriter stringWriter = new StringWriter();
    PrintWriter printWriter = new PrintWriter(stringWriter);
    e.printStackTrace(printWriter);
    String stackTrace = stringWriter.toString();

        return new ResponseEntity<>(
            new ErrorResponse(
              status, 
              e.getMessage(), 
              stackTrace // specifying the stack trace in case of 500s
            ),
            status
        );
    }
}