Spring MVC 컨트롤러 작업에서 외부 URL로 리디렉션하는 방법은 무엇입니까?

@RequestMapping(method = RequestMethod.POST)
public String processForm(HttpServletRequest request, LoginForm loginForm, 
                          BindingResult result, ModelMap model) 
{
    String redirectUrl = "yahoo.com";
    return "redirect:" + redirectUrl;
}

@RequestMapping(method = RequestMethod.POST)
public String processForm(HttpServletRequest request, LoginForm loginForm, 
                              BindingResult result, ModelMap model) 
{
    String redirectUrl = "http://www.yahoo.com";
    return "redirect:" + redirectUrl;
}

@RequestMapping(value = "/redirect", method = RequestMethod.GET)
public void method(HttpServletResponse httpServletResponse) {
    httpServletResponse.setHeader("Location", projectUrl);
    httpServletResponse.setStatus(302);
}

@RequestMapping(value = "/redirect", method = RequestMethod.GET)
public ModelAndView method() {
    return new ModelAndView("redirect:" + projectUrl);
}