@EnableAutoConfiguration
@ComponentScan({"com.example"})
public class Application extends SpringBootServletInitializer {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        return application.sources(Application.class, Initializer.class);
    }

    @Bean
    public ServletRegistrationBean servletRegistrationBean() {
        FacesServlet servlet = new FacesServlet();
        ServletRegistrationBean servletRegistrationBean = new ServletRegistrationBean(servlet, "*.jsf");
        return servletRegistrationBean;
    }

    @Bean
    public FilterRegistrationBean rewriteFilter() {
        FilterRegistrationBean rwFilter = new FilterRegistrationBean(new RewriteFilter());
        rwFilter.setDispatcherTypes(EnumSet.of(DispatcherType.FORWARD, DispatcherType.REQUEST,
                DispatcherType.ASYNC, DispatcherType.ERROR));
        rwFilter.addUrlPatterns("/*");
        return rwFilter;
    }
    @Bean
    public ServletRegistrationBean h2servletRegistration() {
        ServletRegistrationBean registration = new ServletRegistrationBean(new WebServlet());
        registration.addUrlMappings("/console/*");
        return registration;
    }
}

@RewriteConfiguration
public class FacesRewriteConfigurationProvider extends HttpConfigurationProvider {

    @Override
    public int priority()
    {
        return 10;
    }

    @Override
    public Configuration getConfiguration(final ServletContext context)
    {
        return ConfigurationBuilder.begin()
                .addRule(Join.path("/").to("/index.jsf"))
                .addRule(Join.path("/index").to("/index.jsf"))
                .addRule(Join.path("/files").to("/file.jsf"))
                .addRule(Join.path("/register").to("/register.jsf"));
    }
}

@Configuration
public class Initializer implements ServletContextInitializer {
    @Override
    public void onStartup(ServletContext servletContext) throws ServletException {
        System.err.println("------------------------------------");
        servletContext.setInitParameter("primefaces.CLIENT_SIDE_VALIDATION", "true");
        servletContext.setInitParameter("primefaces.THEME", "bootstrap");
    }
}

<h:form id="register" method="post">
            <h:message for="RegisterGroupPanel" style="color:red;" />
            <h:panelGrid columns="3" id="RegisterGroupPanel">
                <h:outputLabel for="username" value="Username : " />
                <h:inputText id="username" value="#{loginBean.username}" required="true"
                             requiredMessage="Please enter username" />
                <h:message for="username" style="color: red;" />

                <h:outputLabel for="password" value="Password : " />
                <h:inputSecret id="password" value="#{loginBean.pwd}" required="true"
                               requiredMessage="Please enter password" />
                <h:message for="password" style="color: red;" />
            </h:panelGrid>

            <h:commandButton action="#{loginBean.userLogin()}" value="Login" />
        </h:form>

@ManagedBean
@SessionScoped
public class LoginBean {

    private String pwd;
    private String username;

    @ManagedProperty(value = "#{userRepository}")
    UserRepository userRepository;

    public String userLogin() throws IOException {
        User currentUser = userRepository.findByUsername(username);
        FacesContext context = FacesContext.getCurrentInstance();

        if (currentUser == null) {
            context.addMessage(null, new FacesMessage("username and password doesn't match, try again"));
            return null;
        } else {
            context.getExternalContext().getSessionMap().put("currentUser", currentUser);
//            context.getExternalContext().getSessionMap().put("testSession", "session working!!!");
            return "index.xhtml?faces-redirect=true";
        }
    }

    public String logout() {
        FacesContext context = FacesContext.getCurrentInstance();
        context.getExternalContext().invalidateSession();
        return "login.xhtml?faces-redirect=true";
    }
}

<application>
        <el-resolver>org.springframework.web.jsf.el.SpringBeanFacesELResolver</el-resolver>
    </application>

<servlet>
        <servlet-name>Faces Servlet</servlet-name>
        <servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>Faces Servlet</servlet-name>
        <url-pattern>*.jsf</url-pattern>
    </servlet-mapping>
    <context-param>
        <param-name>primefaces.CLIENT_SIDE_VALIDATION</param-name>
        <param-value>true</param-value>
    </context-param>
    <context-param>
        <param-name>javax.faces.FACELETS_REFRESH_PERIOD</param-name>
        <param-value>0</param-value>
    </context-param>
    <context-param>
        <param-name>javax.faces.PROJECT_STAGE</param-name>
        <param-value>Development</param-value>
    </context-param>
    <context-param>
        <param-name>facelets.SKIP_COMMENTS</param-name>
        <param-value>true</param-value>
    </context-param>