Spring MVC - custom error page not working [closed]

I have a Spring MVC application, and I want to have a custom error page for certain errors. For example, 404 and 500.

Now, my application can, in a certain condition, throw an exception that causes a 500 status code. Without the custom error page, it looks like this:

Now I want to have a custom error page, so I apply the following web.xml file:

<web-app><error-page><error-code>404</error-code><location>/error404</location></error-page><error-page><error-code>400</error-code><location>/error400</location></error-page><error-page><error-code>500</error-code><location>/error500</location></error-page></web-app>

And the following ErrorController

@Controllerpublic class ErrorController {    @GetMapping("/error404")    public String error404() {        return "html/error404";    }    @GetMapping("/error500")    public String error500() {        return "html/error500";    }}

The 404 works great - if I try to browse to http://localhost:8080/my-app/non-existing-url I get my custom 404 error page.

However, when I cause my application to throw the same exception that caused a 500 to be returned above, I don't get my custom page. Instead, I get:

Can someone help me understand why that is?!

EDIT

I found that when throwing another exception that causes a 500:

then, if I enable the custom error page, I do get my custom error page. So it seems that for specific exceptions it does work but for other it doesn't. What is the logic behind this?