Why does root path in my controller maps to index.html in spring boot web application?

I’m testing a controller for a Spring Boot application. I want to map a resource to a path, which should be a part of my API. My controller is pretty specific about path:

@Controller
public class DefaultController
{
  @RequestMapping("${web-interface}")
  public String main()
  {
    return "index.html";
  }
}

Here ‘web-interface’ is a property, as specified in application.yml file

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/search-engine
    username: landsreyk
    password: 12345678
  jpa:
    database-platform: org.hibernate.dialect.MySQLDialect
    show-sql: false
    hibernate:
      ddl-auto: none
web-interface: /admin

Expected behavior:

path: localhost:8080/admin maps to index.html resource

root path: localhost:8080/ maps to nothing, i.e. 404 error.

Actual behavior:

path: ‘/admin’ maps to index.html

path: ‘/’ also maps to index.html

But why? Shouldn’t I just see “Whitelabel Error Page”. There is no controller, which maps root path to index.html file. It doesn’t make any sense.

By the way, here is my project structure.

Solution:

Rename index.html to any other name, like main.html and root path ‘/’ will no longer map to that resource.

Answer

Root path “/” by defaults maps to index.html. It is standard for all languages and frameworks. index.html is meant to be entry point for your application