//方式1：通过model 将数据绑定
    @RequestMapping(value = "findByIdModel", method = RequestMethod.GET)
    public String findByIdModel(@RequestParam("empno") int id, Model model) {
        
        Emp emp = empService.findById(id);//从业务层传回的数据
        
        model.addAttribute("emp", emp);//将数据绑定
        
        return "findbyid";//返回的页面
    }
//方式2：通过Map 
    @RequestMapping(value = "findByIdMap", method = RequestMethod.GET)
    public String findByIdMap(@RequestParam("empno") int id, Map<String,Object> map) {
        
        Emp emp = empService.findById(id);
        
        map.put("emp", emp);
        
        return "findbyid";
    }
    
    //方式3：通过ModelAndView
    @RequestMapping(value = "findByIdMAV", method = RequestMethod.GET)
    public ModelAndView findByIdMAV(@RequestParam("empno") int id) {
        
        Emp emp = empService.findById(id);
        
//        ModelAndView mav = new ModelAndView("findbyid");
        ModelAndView mav = new ModelAndView();
        
        mav.setViewName("findbyid");//设置返回页面
        
        mav.addObject("emp", emp);//设置action传递的值
        
        System.out.println("use ModelAndView:"+emp);
        
        return mav;
    }