Handling Request Parameters in Spring MVC

This article demonstrates how Spring MVC processes request parameters, covering the use of various annotations and native Servlet API objects.

Servlet style : parameters are retrieved with HttpServletRequest.getParameter("name"). Example:

@WebServlet("/hello")
public class HelloServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // Get parameter value
        String username = req.getParameter("username");
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

@RequestParam : directly bind a request parameter to a method argument.

@Controller
public class HelloController {
    @RequestMapping("/hello")
    public String hello(String username) {
        System.out.println(username);
        return "success";
    }
}

When the parameter name differs from the method argument, specify it with @RequestParam("user"). The required attribute can be set to false to avoid errors, and defaultValue can provide a fallback.

@RequestMapping("/hello")
public String hello(@RequestParam(value = "user", required = false, defaultValue = "zhang") String username) {
    System.out.println(username);
    return "success";
}

@RequestHeader : obtain HTTP header values.

@RequestMapping("/hello")
public String hello(@RequestHeader("User-Agent") String userAgent) {
    System.out.println(userAgent);
    return "success";
}

Set required = false or provide defaultValue to handle missing headers.

@RequestMapping("/hello")
public String hello(@RequestHeader(value = "test", required = false) String userAgent) {
    System.out.println(userAgent);
    return "success";
}

@RequestBody : bind the request body (e.g., JSON) to a method argument or a POJO.

@RequestMapping("/hello")
public String hello(@RequestBody String json) {
    System.out.println(json);
    return "success";
}

Or bind directly to a POJO:

@RequestMapping("/hello")
public String hello(@RequestBody Person person) {
    System.out.println(person);
    return "success";
}

@CookieValue : retrieve cookie values.

@RequestMapping("/hello")
public String hello(@CookieValue("_ga") String ga) {
    System.out.println(ga);
    return "success";
}

Object binding : complex parameters can be bound to a Java object, supporting nested objects via dot notation.

@Data
public class Person {
    private String name;
    private Integer age;
    private Character sex;
    private Address address;
}

@Data
public class Address {
    private String province;
    private String city;
}

Controller method:

@RequestMapping("/hello")
public String hello(Person person) {
    System.out.println(person);
    return "success";
}

Native Servlet API objects : HttpServletResponse, HttpSession, etc., can be injected directly.

@RequestMapping("/hello")
public String hello(HttpServletResponse response) {
    Cookie cookie = new Cookie("test", "test");
    response.addCookie(cookie);
    return "success";
}

@RequestMapping("/hello")
public String hello(HttpSession session) {
    session.setAttribute("test", "test");
    return "success";
}

Character encoding : use CharacterEncodingFilter in web.xml to solve request/response garbled text.

<filter>
    <filter-name>characterEncodingFilter</filter-name>
    <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
    <init-param>
        <param-name>encoding</param-name>
        <param-value>UTF-8</param-value>
    </init-param>
</filter>
<filter-mapping>
    <filter-name>characterEncodingFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

These examples cover the full range of request‑parameter handling techniques in Spring MVC.