bootstrap template & spring boot ( can not display an html page) - spring

Question

I'am using a bootstrap template and spring boot , i wanted to test the controller , for that i code a simple restfull service wich retun the index page of the template but it didn't work it gives me an error.
Here's the architecture of the project
And here's my controller
package demo.controllers;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.web.ErrorController;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.servlet.View;
import org.springframework.web.servlet.config.annotation.ViewControllerRegistry;
import org.springframework.web.servlet.view.RedirectView;
import demo.connection.SingletonConnection;
import demo.dao.IDatabase;
import demo.dao.IEntities;
import demo.entities.DB;
#RestController
public class DatabaseController implements ErrorController{
private static final String PATH = "/error";
protected Connection conn;
#Autowired
private IDatabase db;
#Autowired
private IEntities entities;
// En cas d'érreur
#RequestMapping(value = PATH)
public String error() {
return "Error";
}
#Override
public String getErrorPath() {
return PATH;
}
#RequestMapping(value="/")
public String index(Model model){
return "pages/index.html";
}
}
when i run the application with the path : http://localhost:8080/test