Need help, this made my head spin. Look at the code

This does not work
Code:
@Controller
public class EmployeeProfileController {

    @RequestMapping("/expenses_employee")
    public Object index(HttpSession session) {
        ModelAndView mv = new ModelAndView("home");
        
        return mv;
    }
}
However, this does

Code:
@Controller
public class EmployeeProfileController {

    @RequestMapping("/expenses_employee")
    public Object index(HttpSession session) {
        
        return "home";
    }
}
I used this as resolver
Code:
<bean id="viewResolver"
        class="org.springframework.web.servlet.view.UrlBasedViewResolver">
        <property name="viewClass"
            value="org.springframework.web.servlet.view.JstlView" />
        <property name="prefix" value="/WEB-INF/jsp/" />
        <property name="suffix" value=".jsp" />
        <property name="order" value="1" />
    </bean>
The weird thing is that 2 of my controllers having EXACTLY the same code, works for both cases.
The problem is that I need to pass variables to the View from the Controller.

Note that this is only a sample code, if the code logic did not make sense just ignore it. I just want to know why it does not work.

I am becoming desperate here
Please I need help.
Thank you for any help you can provide.