Return Html page using RestController in Spring Boot

Question

I am trying to get the HTML page that I created. This is the structure of my project:

This is the "IndexController" class:

@RestController
@AllArgsConstructor
@RequestMapping(path = "/webpage")
public class IndexController {

        @GetMapping(path = {"mainpage"})
        @ResponseBody
        public String index(){
            return "Index";
        }
    
        @PostMapping("/check")
        public String CheckDataset(@ModelAttribute CheckModel checkModel){
            System.out.println(checkModel);
            return null;
        }
    
    }

When I open the HTML webpage directly from intellij:

Is opening perfectly, but when I am trying to open the HTML from Spring Boot is returning just the "Index" String.

Do you have any idea how to solve this?

Answer 1

Please note that your class IndexController shall not have @RestController if you need to show an HTML page. It shall only have @Controller.

In simple terms @RestController = @Controller + @ResponseBody

In your case, the @RestController annotation you used makes all the methods within it @ResponseBody by default, and you don't have to explicitly mention

@ResponseBody annotation doesn't show the view instead it sends a String response.

Steps to fix this issue:

1. Change @RestController annotation to @Controller in class level
2. Remove @ResponseBody from the method in which you're planning to show the HTML

So your code will be

@Controller
@AllArgsConstructor
@RequestMapping(path = "/webpage")
public class IndexController {

    @GetMapping(path = {"mainpage"})
    public String index(){
        return "Index";
    }

   //Other methods
    
}

Just make sure you have spring-boot-starter-thymeleaf dependency in your POM.xml

Thanks.