Spring boot redirect to error page when catch the thymeleaf exception

Question

I would like to redirect to my custom error page (/error/page) when a Thymeleaf error happens (ie fragment doesn't exist).

My problem is that the whole error page gets rendered into the Thymeleaf fragment if it has any errors.

I have tried writing a custom error handler, and a custom error controller, and it works fine for any other exceptions (redirects to my custom error page), but not when a Thymeleaf error happens.

    @Controller
    public class CustomErrorController implements ErrorController {
    
        private final String ERROR_PATH = "/error";
    
        @RequestMapping(ERROR_PATH)
        public String handleError(HttpServletRequest request) {
            Object status = request.getAttribute(RequestDispatcher.ERROR_STATUS_CODE);
    
            if (status != null) {
                int statusCode = Integer.parseInt(status.toString());
    
                if (statusCode == HttpStatus.NOT_FOUND.value()) {
                    return "redirect:/error/page";
                } else if (statusCode == HttpStatus.INTERNAL_SERVER_ERROR.value()) {
                    return "redirect:/error/page";
                }
            }
            // Thymeleaf error -> status code 200 and doesn't work redirect
            return "redirect:/error/page";
        }
    
        @Override
        public String getErrorPath() {
            return ERROR_PATH;
        }
    
        @ModelAttribute(name = "url")
        public String getUrl(@AuthenticationPrincipal User user) {
            return user != null
                    ? "rooms"
                    : "";
        }
    }

    @Controller
    public class DefaultErrorController {
    
        @RequestMapping("/error/page")
        public String handleError() {
            return "errors/error";
        }
    
        @ModelAttribute(name = "url")
        public String getUrl(@AuthenticationPrincipal User user) {
            return user != null
                    ? "rooms"
                    : "";
        }
    
    }

    public class ThymeleafErrorFilter implements Filter {
    
        @Override
        public void init(final FilterConfig filterConfig) {
    
        }
    
        @Override
        public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
            try {
                filterChain.doFilter(servletRequest, servletResponse);
            } catch (final NestedServletException nse) {
                if(nse.getCause() instanceof TemplateEngineException) {
                    // redirec to error page
                }
                throw nse;
            }
        }
    
        @Override
        public void destroy() {
        }
    }

Application.properties:

    ############## ERROR PAGE ################
    server.error.whitelabel.enabled=false
    server.error.path=/error

@EnableAutoConfiguration AppConfig.java

    @Bean
    public FilterRegistrationBean<ThymeleafErrorFilter> thymeleafErrorFilter() {
        var thymeleafErrorFilter = new FilterRegistrationBean<ThymeleafErrorFilter>();
        thymeleafErrorFilter.setName("thymeleafErrorFilter");
        thymeleafErrorFilter.setFilter(new ThymeleafErrorFilter());
        thymeleafErrorFilter.addUrlPatterns("/*");
        return thymeleafErrorFilter;
    }

If thymeleaf fragments don't exist. We detected it in ThymeleafErrorFilter. After the spring call /error (we catch it in CustomErrorController) and in CustomErrorController, the status code is 200, and redirect doesn't work.

Answer 1

You should use @ControllerAdvise to handle your Exceptions and provide a view to render the error.

See this:

@ControllerAdvice
@Slf4j
public class ErrorControllerAdvice {
 

    @ExceptionHandler(StorageException.class)  //handle this exception
    @ResponseStatus(HttpStatus.INTERNAL_SERVER_ERROR)
    public String storageException(final StorageException throwable, final Model model) {
        log.error("Exception during execution of application", throwable);
        model.addAttribute("errorMessage", "Failed to store file"); //custom message to render in HTML
        return "error";  //the html page in resources/templates folder
    }


/// handle other exeptions

The view:

error.html

<h1> Opps.. Sorry about this. </h1>
<p th:utext="${errorMessage}"></p>

See https://github.com/gtiwari333/spring-boot-blog-app/blob/master/src/main/java/gt/app/web/mvc/ErrorControllerAdvice.java for more details.