Fix location path to .css with Thymeleaf (Spring Boot)

Question

I'm working on a project with Spring Boot. I have a main.css file under /src/main/resources/static/css/

I use this thymeleaf code to inject the.css file into a.html file from the /templates folder:

<link rel="stylesheet" th:href="@{/css/main.css}" href="../static/css/main.css" />  

I can open it respectively via http://localhost:1126/css/main.css

I use this.html as a detailed error page. So if an URL doesn't exists, show this.html. If the URL is with "one depth" (for example localhost:1126/something ) it works fine (.html is shown and.css is loaded).
But if I use URLs with at least "two depths", or even with an "/" at the end (for example localhost:1126/something/ or localhost:1126/something/anything ) it doesn't work (.html is shown but.css IS NOT loaded).

The problem is that in the second case Spring try to find the.css file under localhost:1126/something/css/main.css

Things I've tried so far:
use th:href="@{/css/main.css}" instead of th:href="@{css/main.css}"

AND

@SpringBootApplication
@EnableWebMvc
public class SpringBootProjectApplication implements WebMvcConfigurer {
    public static void main(String[] args) {
    SpringApplication.run(SpringBootProjectApplication.class, args);
    }
    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/css/**").addResourceLocations("classpath:/css/");
    }
}

I have found these threads with no answers for my problem:

Thymeleaf, IntelliJ and Spring Boot not loading CSS files correctly
Spring Boot, Thymeleaf and CSS
CSS file cannot be located thymeleaf Spring Boot

Answer 1

Spring boot default BasicErrorController would directly look at src/main/resources/templates/ folder if you add your error html page there as "error.html" you can show that whenever error occurs

Answer 2

I faced the same issue when my URL had multiple "/". But I did not make any special changes except for changing my css links as follows.

<link rel="stylesheet" th:href="@{~/css/main.css}">

And same with javascript files as well.

On a side note, I don't use @EnableWebMvc annotation. It kinda messes up with automatic SpringMVC configuration.