Spring boot 如何在Spring Boot的控制器类中使用if-else重定向到另一个视图？例如：

这里，我有一个名为validLogin的控制器类，它返回模型和视图。我通过登录表单传递了两个参数，并确定这些参数是否存在于我的数据库中。我现在的问题是，如果数据库中没有参数，如何重定向到else{}块中的另一个视图

@RequestMapping(path = "/validLogin")
    public ModelAndView validLogin(@RequestParam(name = "email", defaultValue = "retryEmail") String email,
            @RequestParam(name = "password", defaultValue = "retryPass") String password) {
        ModelAndView mv=new ModelAndView();
        RegisteredUsers s1=docDao.findByEmailAndPassword(email,password);
        mv.addObject("email",email);
        mv.addObject("password",password);
        mv.addObject(s1);
        mv.setViewName("validLogin.jsp");
        System.out.println("email id: " + email+" password : " + password);
        if(s1 != null) {
            System.out.println("Value exists..");
        }else {

        }
        return mv;
    }

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试试这个：当出现问题时，你需要有一个错误页面作为你的目标

  @RequestMapping(path = "/validLogin")
        public ModelAndView validLogin(@RequestParam(name = "email", defaultValue = "retryEmail") String email,
                @RequestParam(name = "password", defaultValue = "retryPass") String password) {
            ModelAndView mv=new ModelAndView();
            RegisteredUsers s1=docDao.findByEmailAndPassword(email,password);
            mv.addObject("email",email);
            mv.addObject("password",password);
            mv.addObject(s1);
            mv.setViewName("validLogin.jsp");
            System.out.println("email id: " + email+" password : " + password);
            if(s1 != null) {
                System.out.println("Value exists..");
            return mv;
            }else {
            return new ModelAndView("errorView.jsp");
            }

        }

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当RegisteredUsers不为null时，移动向模型添加数据的bloc

@RequestMapping(path = "/validLogin")
 public ModelAndView validLogin(@RequestParam(name = "email", defaultValue = "retryEmail") String email, @RequestParam(name = "password", defaultValue = 
 "retryPass") String password) {
 ModelAndView mv=new ModelAndView();
 RegisteredUsers s1=docDao.findByEmailAndPassword(email,password);            
 System.out.println("email id: " + email+" password : " + password);
 if(s1 != null) {
 System.out.println("Value exists..");
 mv.addObject("email",email);
 mv.addObject("password",password);
 mv.addObject(s1);
 mv.setViewName("validLogin.jsp");
 return mv;
 }else {
return new ModelAndView("errorView.jsp");
}
}

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现在它的工作，因为它应该是…非常感谢！