springboot obtains the URL request parameters in a number of ways

1. Write the form parameters directly in the formal parameters of the corresponding Controller method, which is applicable to get submission but not post submission.

 /**
   * 1. Write the form's parameters directly in Controller Of the corresponding method 
   * @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";
  }

url forms: http: / / localhost SSMDemo/demo/addUser1 & # 63; username=lixiaoxi & password=111111 The submitted parameter needs to be the same as the input name 1 in the Controller method.

2. It can be received by HttpServletRequest, post and get.

  /**
   * 2 And through HttpServletRequest receive 
   * @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. It can be received by one bean, either post or get.

(1) Set up an bean corresponding to the parameters in the form

package demo.model;
public class UserModel {
  private String username;
  private String password;
  public String getUsername() {
    return username;
  }
  public void setUsername(String username) {
    this.username = username;
  }
  public String getPassword() {
    return password;
  }
  public void setPassword(String password) {
    this.password = password;
  }
}

(2) This bean is used to encapsulate the received parameters

/**
   * 3 And through 1 a bean To receive the 
   * @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. Get the parameters in the path through @PathVariable

 /**
   * 4 And through @PathVariable Gets the parameters in the path 
   * @param username
   * @param password
   * @return
   */
  @RequestMapping(value="/addUser4/{username}/{password}",method=RequestMethod.GET)
public String addUser4(@PathVariable String username,@PathVariable String password) {
    System.out.println("username is:"+username);
    System.out.println("password is:"+password);
    return "demo/index";
  }

Visit http: for example, / / localhost SSMDemo/demo/addUser4 / lixiaoxi / 111111 paths, then automatically URL template variables in {username} and {password} is bound to the through @ PathVariable annotations on the parameters of the same name, namely the username = lixiaoxi, password = 111111 refs.

5. Use the @ModelAttribute annotation to obtain the FORM form data requested by POST

The Jsp form is as follows:

<form action ="<%=request.getContextPath()%>/demo/addUser5" method="post"> 
    The user name :&nbsp;<input type="text" name="username"/><br/>
    The secret &nbsp;&nbsp; code :&nbsp;<input type="password" name="password"/><br/>
   <input type="submit" value=" submit "/> 
   <input type="reset" value=" reset "/> 
</form>

Java Controller is as follows:

  /**
   * 5 , the use of @ModelAttribute Annotations to obtain POST The request of FORM The form data 
   * @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";
  }

6. Use the annotation @RequestParam to bind the request parameter to the method

An exception occurs when the request parameter username does not exist, which can be resolved by setting the property required=false, for example: @RequestParam (value="username", required=false)

 /**
   * 6 , with annotations @RequestParam Bind request parameters to method parameters 
   * @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";
  }

conclusion