How do I create a 404 controller using Spring Boot? - spring

Question

I'd like to return a custom 404 error using SpringBoot, but I'd like to be able to add some server-side logic to it, not just serve a static page.
1. I switched off the default whitelabel page in application.properties
error.whitelabel.enabled=false
2. I added a Thymeleaf error.html under resources/templates
This works by the way. The page is served, but no controller is called.
3. I created a class Error to be the "Controller"
package com.noxgroup.nitro.pages;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RequestMapping;
#Controller
#RequestMapping("/error")
public class Error {
#ExceptionHandler
public String index() {
System.out.println("Returning Error");
return "index";
}
}
Unfortunately, I'm not seeing Returning Error printed anywhere in the console.
I'm using the Embedded Tomcat with Spring Boot. I've seen various options, non of which seem to work including using #ControllerAdvice, removing the RequestMapping, etc. Neither work for me.

Answer 1

The servlet container is going to pick up the 404 before it can get to Spring, so you'll need to define an error page at servlet container level, which forwards to your custom controller.
#Component
public class CustomizationBean implements EmbeddedServletContainerCustomizer {
#Override
public void customize(ConfigurableEmbeddedServletContainer container) {
container.addErrorPages(new ErrorPage(HttpStatus.NOT_FOUND, "/error"));
}
}

Answer 2

Easiest way I found was to implement the ErrorController.
#Controller
public class RedirectUnknownUrls implements ErrorController {
#GetMapping("/error")
public void redirectNonExistentUrlsToHome(HttpServletResponse response) throws IOException {
response.sendRedirect("/");
}
#Override
public String getErrorPath() {
return "/error";
}
}