I tried to run spring boot application, that will return me the HTML static file on the static folder, the problem was: every time I load the page: 127.0.0.1 I get the String \"
@Controller VS @RestController
@Controller is used to mark classes as Spring MVC Controller. @RestController is a convenience annotation that does nothing more than adding the @Controller and @ResponseBody annotations.So in your case just removing the @ResponseBody annotation from the welcome() method in HomeController.java, should be enough to get the desired output.
Also have a look at this Spring Guide displaying how to Serve Web Content with Spring MVC