title: @SessionAttributes not working properly for consecutive get requests
body: <p>Before asking question first i describe the scenario. I have multiple servlet contexts. suppose <code>/**book**/review</code> url is corresponding to book-servlet.xml and <code>/**report**/update</code> corresponds to report-servlet.xml.</p>
  
  <p>Here are two controllers</p>
  
  <pre><code>@Controller
  @SessionAttributes(BookController.COMMAND_NAME)
  public class BookController {
  
      public static final String COMMAND_NAME = "login";
  
      @GetMapping("/book/review")
      public String show(ModelMap modelMap) {
  
          modelMap.put(COMMAND_NAME, getBook());
  
          return "redirects:" + "/report/update"; //it redirects to second controller method
      }
  }
  
  @Controller
  @SessionAttributes(ReportController.COMMAND_NAME)
  public class ReportController {
  
      public static final String COMMAND_NAME = "report";
  
      @GetMapping("/report/update")
      public String show(ModelMap modelMap) {
  
          modelMap.put(COMMAND_NAME, getReport());
  
          return "redirects:" + "/report/done";
      }
  }
  </code></pre>
  
  <p>Observe this two controller. When i put <code>getBook()</code> in model it stores this object in session after method excution since <code>@SessionAttributes(BookController.COMMAND_NAME)</code> is added above class definition. But, after redirection to <code>/report/update</code> (different servlet context) we are also trying to put <code>getReport()</code> in model. And after handler method excution spring should put the object in session as it does for first case.Unfortunately for second controller it doesn't store it in session.</p>
  
  <p>My question is if the first controller method can successfully save it in session why the second controller can't? Or is it for servlet context switching / multiple get requests or something like this. Please i need to know the reason it behaves weirdly. I am now totally confused about @SessionAttributes. It should work same for both controllers. </p>