/**
   * 1.直接把表单的参数写在Controller相应的方法的形参中
   * @param username
   * @param password
   * @return
   */
  @RequestMapping("/addUser1")
  public String addUser1(String username,String password) {
    System.out.println("username is:"+username);
    System.out.println("password is:"+password);
    return "demo/index";
  }

　/**
   * 2、通过HttpServletRequest接收
   * @param request
   * @return
   */
  @RequestMapping("/addUser2")
  public String addUser2(HttpServletRequest request) {
    String username=request.getParameter("username");
    String password=request.getParameter("password");
    System.out.println("username is:"+username);
    System.out.println("password is:"+password);
    return "demo/index";
  }

　　/**
   * 3、通过一个bean来接收
   * @param user
   * @return
   */
  @RequestMapping("/addUser3")
  public String addUser3(UserModel user) {
    System.out.println("username is:"+user.getUsername());
    System.out.println("password is:"+user.getPassword());
    return "demo/index";
  }

/**
   * 4、使用@ModelAttribute注解获取POST请求的FORM表单数据
   * @param user
   * @return
   */
  @RequestMapping(value="/addUser5",method=RequestMethod.POST)
  public String addUser5(@ModelAttribute("user") UserModel user) {
    System.out.println("username is:"+user.getUsername());
    System.out.println("password is:"+user.getPassword());
    return "demo/index";
  }

@RequestParam(value="username", required=false)
　　**** 若"Content-Type"="application/x-www-form-urlencoded"，post get都可以
　　**** 若"Content-Type"="application/application/json"，只适用get
 　　/**
   * 5、用注解@RequestParam绑定请求参数到方法入参
   * @param username
   * @param password
   * @return
   */
  @RequestMapping(value="/addUser6",method=RequestMethod.GET)
  public String addUser6(@RequestParam("username") String username,@RequestParam("password") String password) {
    System.out.println("username is:"+username);
    System.out.println("password is:"+password);
    return "demo/index";
  }

　　@RequestMapping(value="/addUser6",method=RequestMethod.GET)
  public String addUser6(HttpServletRequest request) { 
　　　　System.out.println("username is:"+request.getQueryString()); 
　　　　return "demo/index"; 
　　}