SpringBoot and Angular JS route not traversing to proper page - angularjs

Question

I have used Spring Boot and Angular JS application. My home page is getting viewed from my controller but routing to new page using angular is not happening,
Angular JS - code
use strict
var demoApp = angular.module('app', [ 'ngRoute']);
//configure our routes
demoApp.config(function($routeProvider) {
$routeProvider
// route for the home page
.when('/', {
templateUrl: 'home.html',
controller: 'mainController'
})
// route for the about page
.when('/about', {
templateUrl: 'views/about.html',
controller: 'aboutController'
})
// route for the contact page
.when('/contact', {
templateUrl: 'contact.html',
controller: 'contactController'
});
});
// create the controller and inject Angular's $scope
demoApp.controller('mainController', function($scope) {
// create a message to display in our view
$scope.HomeMessage = 'Home Controller Called !!!';
});
demoApp.controller('aboutController', function($scope) {
$scope.AboutMessage = 'About Controller Called !!!';
});
demoApp.controller('contactController', function($scope) {
$scope.ContactMessage = 'Contact Controller Called !!!';
});
Spring Boot Code
#RequestMapping("/main")
#Controller
public class HomeController {
#RequestMapping("/")
public String home() {
return "home";
}
}
I am getting my home page but from my html I am traversing to about and contact page where routing is not happening
HTML Code
<ul class="nav navbar-nav navbar-right ">
<li><i class="fa fa-home"></i>Home</li>
<li><i class="fa fa-shield"></i>About</li>
<li><i class="fa fa-comment"></i>Contact
</li>
</ul>
This is the home page it is displaying http://localhost:8080/main/#!/ and if I try to traverse to contact or about it is displaying the same page and it is appending "!" mark
http://localhost:8080/main/#!/#about. Can anyone suggest how is it possible to traverse to new page
Got this below error in console
Error: [$compile:tpload] Failed to load template:
home.html (HTTP status: 404 )
http://errors.angularjs.org/1.6.9/$compile/tpload?p0=home.html&p1=404&p2=
at angular.js:116