URL Parameter Binding

@RequestParam Annotation

For URL parameters in format ?username=value&password=value, use @RequestParam annotation:

@RequestMapping("/auth.do")
public ModelAndView authenticate(
    @RequestParam("username") String userName,
    @RequestParam(value = "password", required = false) String userPassword) {
    
    ModelAndView mv = new ModelAndView("Dashboard");
    System.out.println("User: " + userName + " Password: " + userPassword);
    return mv;
}

@PathVariable Annotation

For REST-style URLs like /user/{id}/{role}, use @PathVariable:

@RequestMapping(value = "/profile/{userId}/{role}", method = RequestMethod.GET)
public ModelAndView loadProfile(
    @PathVariable("userId") String userId,
    @PathVariable("role") String userRole) {
    
    ModelAndView mv = new ModelAndView("Profile");
    System.out.println("ID: " + userId + " Role: " + userRole);
    return mv;
}

Form Data Binding

Direct Parameter Binding

HTML form with input fields:

<form method="post" action="/submit.do">
    Username: <input type="text" name="userName"/>
    Password: <input type="password" name="userPass"/>
    <input type="submit"/>
</form>

Controller method with matching parameter names:

@RequestMapping(value = "/submit.do", method = RequestMethod.POST)
public ModelAndView processForm(String userName, String userPass) {
    ModelAndView mv = new ModelAndView("Result");
    System.out.println("Username: " + userName + " Password: " + userPass);
    return mv;
}

POJO Object Binding

User entity class:

public class UserAccount {
    private String userName;
    private String userPass;
    
    public String getUserName() { return userName; }
    public void setUserName(String userName) { this.userName = userName; }
    public String getUserPass() { return userPass; }
    public void setUserPass(String userPass) { this.userPass = userPass; }
}

Controller using object binding:

@RequestMapping("/register.do")
public ModelAndView registerUser(UserAccount account) {
    ModelAndView mv = new ModelAndView("Welcome");
    System.out.println("User: " + account.getUserName() + 
                      " Pass: " + account.getUserPass());
    return mv;
}

Servlet API Parameter Access

@RequestMapping("/process.do")
public ModelAndView processRequest(HttpServletRequest req) {
    String username = req.getParameter("userName");
    System.out.println("Username: " + username);
    return new ModelAndView("Output");
}

Array Parameter Binding

Form with multiple checkboxes:

<form method="post" action="/preferences.do">
    <input type="checkbox" name="interests" value="sports" />Sports
    <input type="checkbox" name="interests" value="music" />Music
    <input type="checkbox" name="interests" value="reading" />Reading
    <input type="submit"/>
</form>

Controller handling array parameters:

@RequestMapping(value = "/preferences.do", method = RequestMethod.POST)
public ModelAndView savePreferences(String[] interests) {
    ModelAndView mv = new ModelAndView("Preferences");
    for (String interest : interests) {
        System.out.println("Interest: " + interest);
    }
    return mv;
}

Date Parameter Binding

Custom date binding configuration:

@InitBinder
protected void initBinder(WebDataBinder binder) {
    SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
    dateFormat.setLenient(false);
    binder.registerCustomEditor(Date.class, new CustomDateEditor(dateFormat, true));
}

Form with date input:

<form method="post" action="/birthday.do">
    Birth Date: <input type="date" name="birthDate"/>
    <input type="submit"/>
</form>

Controller with date parameter:

@RequestMapping(value = "/birthday.do", method = RequestMethod.POST)
public ModelAndView recordBirthday(Date birthDate) {
    ModelAndView mv = new ModelAndView("Birthday");
    System.out.println("Birth Date: " + birthDate);
    return mv;
}