Spring rest controller not returning html

I'm using spring boot 1.5.2 and my spring rest controller looks like this

@RestController
@RequestMapping("/")
public class HomeController {

    @RequestMapping(method=RequestMethod.GET)
    public String index() {
        return "index";
    }

}

when I go to http://localhost:8090/assessment/ it reaches my controller but doesn't return my index.html, which is in a maven project under src/main/resources or src/main/resources/static. If I go to this url http://localhost:8090/assessment/index.html, it returns my index.html. I looked at this tutorial https://spring.io/guides/gs/serving-web-content/ and they use thymeleaf. Do I have to use thymeleaf or something like it for my spring rest controller to return my view?

My application class looks like this

@SpringBootApplication
@ComponentScan(basePackages={"com.pkg.*"})
public class Application {

    public static void main(String[] args) throws Exception {
        SpringApplication.run(Application.class, args);
    }
}

When I add the thymeleaf dependency to my classpath I get this error (500 response code)

org.thymeleaf.exceptions.TemplateInputException: Error resolving template "index", template might not exist or might not be accessible by any of the configured Template Resolvers

I guess I do need thymeleaf? I'm going to try and configure it properly now.

It works after changing my controller method to return index.html like this

@RequestMapping(method=RequestMethod.GET)
public String index() {
    return "index.html";
}

I think thymeleaf or software like it allows you to leave off the file extension, not sure though.

Solution

Your example would be something like this:

Your Controller Method with your route "assessment"

@Controller
public class HomeController {

    @GetMapping("/assessment")
    public String index() {
        return "index";
    }

}

Your Thymeleaf template in "src/main/resources/templates/index.html"

<!DOCTYPE HTML>
<html xmlns:th="http://www.thymeleaf.org">
<head>
    <title>Getting Started: Serving Web Content</title>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
</head>
<body>
    <p>Hello World!</p>
</body>
</html>