int i = Integer.parseInt(id); //为啥会空指针异常

Question

@RequestMapping(value = "/login")
public ModelAndView login(HttpServletRequest request) {
String id = request.getParameter("id");
int i = Integer.parseInt(id); //这行代码空指针异常
User user = userService.findById(i);
System.out.println(user);
ModelAndView modelAndView = new ModelAndView();
modelAndView.setViewName("user");
modelAndView.addObject("user",user);
return modelAndView;

Answer 1

给 int i = Integer.parseInt(id)添加一个判断条件。
如有帮助，望采纳

@RequestMapping(value = "/login")
    public ModelAndView login(HttpServletRequest request) {
        String id = request.getParameter("id");
        if (!id.trim().equals("")&&id!=null){
//            判断如果id不为空
            int i = Integer.parseInt(id); //这行代码空指针异常
            User user = userService.findById(i);
            System.out.println(user);
            ModelAndView modelAndView = new ModelAndView();
            modelAndView.setViewName("user");
            modelAndView.addObject("user",user);
            return modelAndView;
        }else {
            //id如果为空，则给他赋值为0
            int i = 0; 
            User user = userService.findById(i);
            System.out.println(user);
            ModelAndView modelAndView = new ModelAndView();
            modelAndView.setViewName("user");
            modelAndView.addObject("user",user);
            return modelAndView;
        }
            
        }