Aside from JEE Filter implementation, let us use aspect to intercept some request-response transactions:

1. Aside from implementing Filter, one obvious solution to monitor sessions during pre and post login transactions is to create interceptors. In the package org.packt.aop.transaction.controller, create a LoginController that will provide a login form and an employee list results page:

@Controller 
public class LoginController { 
   
  @Autowired 
  private EmployeeService employeeServiceImpl; 
   
  @RequestMapping(value="/login_emps.html", 
      method=RequestMethod.GET) 
  public String login(Model model, HttpServletRequest req){ 
     
    int browserNo = (Integer)     
        req.getAttribute("browserNo"); 
    if(browserNo == 3){ 
      model.addAttribute("error", "Browser Not Supported"); 
      return "browser_error"; 
    } 
    return "login";   
  } 
   
  @RequestMapping(value="/login_emps.html", 
      method=RequestMethod.POST) 
  public ModelAndView loginSubmit(ModelMap model, 
    @RequestParam("username") String username, 
    @RequestParam("password") String password){ 
 
    // refer to sources 
    return new    
       ModelAndView("redirect:/menu_emps.html",model); 
  } 
   
  @RequestMapping(value="/menu_emps.html", 
      method=RequestMethod.GET) 
  public String menu(Model model, HttpServletRequest req){ 
     
    List<Employee> emps =    
       employeeServiceImpl.readEmployees(); 
    model.addAttribute("emps", emps); 
    return "menu"; 
  } 
   
  @RequestMapping(value="/empty_login.html", 
      method=RequestMethod.GET) 
  public String emptylogin(){   
      // refer to sources   
  } 
   
  @RequestMapping(value="/browser_error.html", 
      method=RequestMethod.GET) 
  public String browserError(){ 
       // refer to sources  
   } 
} 

2. Create an @Aspect class that will intercept /login_emps.html in processing the incoming HttpServletRequest. The class will filter and check the browser type of the user and will trigger the /browser_error.html page if the application is accessed through Internet Explorer:

@Component 
@Aspect 
public class LoginProxyAspect { 
   
  private Logger logger = 
      Logger.getLogger(LoginProxyAspect.class); 
   
  @Pointcut("within(@org.springframework 
  .stereotype.Controller *))") 
  public void classPointcut() {  } 
   
  @Pointcut("execution(*    
  org.packt.aop.transaction.controller 
  .LoginController.login(..))") 
  public void loginPointcut() {  } 
   
  @Before("classPointcut() && loginPointcut() 
  && args(model,req) && @annotation(mapping)") 
  public String browserCheck(JoinPoint joinPoint,  
     Model model, HttpServletRequest req,  
    RequestMapping mapping) throws ServletException,  
      IOException{ 
   
     logger.info("executing " + 
        joinPoint.getSignature().getName()); 
     logger.warn("MVC application trying to 
check browser type..."); 
     String loginRequestMethod =    
          mapping.method()[0].name(); 
     String username = req.getParameter("username"); 
     String password = req.getParameter("password"); 
     req.setAttribute("username", username); 
     req.setAttribute("password", password); 
     logger.info("executing " + 
        joinPoint.getSignature().getName() + " which is a " 
           + loginRequestMethod + " request"); 
     if(loginRequestMethod.equalsIgnoreCase("GET")){ 
          Enumeration<String> headers =     
              req.getHeaderNames(); 
          while(headers.hasMoreElements()){ 
          String headerName = headers.nextElement();    
          if(headerName.equalsIgnoreCase("user-agent")){ 
              String browserType =  
                  req.getHeader(headerName); 
              if(browserType.contains("Chrome")){ 
                 req.setAttribute("browserNo", 1);   
                 logger.info("MVC application uses  
                     Chrome..."); 
              }else if (browserType.contains("Firefox")){ 
                  req.setAttribute("browserNo", 2); 
                  logger.info("MVC application uses 
                     Firefox..."); 
                  }else{ 
                     req.setAttribute("browserNo", 3); 
                     logger.info("MVC appstops..."); 
                   } 
                 break; 
              } 
            } 
       } 
    return "login"; 
  } 
} 

3. Save all files. Then clean, build, and deploy the ch05 project.