在签名中没有RedirectAttributes的方法中访问RedirectAttributes

Question

Is it possible to access RedirectAttributes in method without RedirectAttributes in signature? For example, when overriding method like one below:

@Override
public void onAuthenticationSuccess(final HttpServletRequest req, final HttpServletResponse res,
        final Authentication auth) throws IOException, ServletException {

    // add something to RedirectAttributes here
    // redirectAttributes.addFlashAttribute("attr", "value");

    super.onAuthenticationSuccess(req, res, auth);
}

I'm using spring 3.2.2.RELEASE.

Answer 1

As you can see in the DispatcherServlet class implementation, there are constants:

public static final String FLASH_MAP_MANAGER_BEAN_NAME = "flashMapManager";
public static final String OUTPUT_FLASH_MAP_ATTRIBUTE = DispatcherServlet.class.getName() + ".OUTPUT_FLASH_MAP";
public static final String FLASH_MAP_MANAGER_ATTRIBUTE = DispatcherServlet.class.getName() + ".FLASH_MAP_MANAGER";

Spring has a class called RequestContextUtils, which has methods:

public static Map<String, ?> getInputFlashMap(HttpServletRequest request)
public static FlashMap getOutputFlashMap(HttpServletRequest request)    
public static FlashMapManager getFlashMapManager(HttpServletRequest request)

The first two methods will give you an access to input and output flash maps respectively. The last method returns FlashMapManager, which has a number of convinient methods to work with flash attributes. See implementations of this interface for details, specifically AbstractFlashMapManager.

Answer 2

If your goal is "to add indication that the customer has landed on the home page for the first time," then HttpSession may do the trick:

@Override
public void onAuthenticationSuccess(HttpServletRequest request, HttpServletResponse response, Authentication authentication)
      throws IOException
{
    ...
    boolean firstLogin = <determine whether this is the first login>;
    <reset condition that caused firstLogin to be true>;
    ...
    HttpSession session = request.getSession(false);
    if (session != null) {
        session.setAttribute("firstLogin", firstLogin);
    }
    else {
        log.debug("No session");
    }
}

// Controller for some page
@RequestMapping(value = <your page>, method = RequestMethod.GET)
public String showPage(<some other args>, HttpSession session)
{
    ...
    Object firstLogin = session.getAttribute("firstLogin");
    Assert.isInstanceOf(Boolean.class, firstLogin, "firstLogin");
    if ((Boolean)firstLogin) {
        <handle first login>;
    }
    ...
    return <page>;
}

This works for me. The logic behind this is that the login is in the context of the entire session that, presumably, comprises multiple requests.