Understanding Spring MVC Annotations: @RequestMapping, @PathVariable, @RequestParam, @CookieValue and RESTful Request Handling

Spring MVC provides a rich set of annotations that simplify request handling. @RequestMapping maps URLs to controller classes or methods and supports pattern matching with ?, *, and ** for flexible path definitions.

@RequestMapping("/testRequestMapping")
public String testRequestMapping(){
    System.out.println("testRequestMapping");
    return SUCCESS;
}

When placed on a class, the annotation defines a common prefix for all methods in that class.

@RequestMapping("/springmvc")
@Controller
public class SpringMVCTest {
    // ...
}

The @PathVariable annotation binds URL placeholders to method parameters, enabling extraction of values directly from the path.

@RequestMapping("/testPathVariable/{id}")
public String testPathVariable(@PathVariable(value="id") Integer id){
    System.out.println("testPathVariable:" + id);
    return SUCCESS;
}

In the view, a link such as

<a href="springmvc/testPathVariable/1">testPathVariable</a>

triggers the method and passes the value 1 to the parameter.

The @RequestParam annotation retrieves query‑string parameters. It can specify default values and whether the parameter is required.

@RequestMapping(value="/testRequestParam")
public String testRequestParam(@RequestParam(value="username") String username,
                               @RequestParam(value="age", required=false, defaultValue="0") int age){
    System.out.println("testRequestParam username:" + username + " age:" + age);
    return SUCCESS;
}

A corresponding link in the JSP like

<a href="springmvc/testRequestParam?username=jackie&age=12">testRequestParam</a>

passes the parameters to the method.

To support RESTful CRUD operations, Spring MVC can handle PUT and DELETE methods by using the HiddenHttpMethodFilter . The filter converts a POST request that contains a hidden input named _method into the desired HTTP method.

@RequestMapping(value="/testRest/{id}", method=RequestMethod.PUT)
public String testRestPut(@PathVariable(value="id") Integer id){
    System.out.println("test put:" + id);
    return SUCCESS;
}

@RequestMapping(value="/testRest/{id}", method=RequestMethod.DELETE)
public String testRestDelete(@PathVariable(value="id") Integer id){
    System.out.println("test delete:" + id);
    return SUCCESS;
}

@RequestMapping(value="/testRest", method=RequestMethod.POST)
public String testRest(){
    System.out.println("test post");
    return SUCCESS;
}

@RequestMapping(value="/testRest/{id}", method=RequestMethod.GET)
public String testRest(@PathVariable(value="id") Integer id){
    System.out.println("test get:" + id);
    return SUCCESS;
}

In the JSP, forms use a hidden field to indicate the intended method:

<form action="springmvc/testRest/1" method="post">
    <input type="hidden" name="_method" value="PUT"/>
    <input type="submit" value="testRestPut"/>
</form>

<form action="springmvc/testRest/1" method="post">
    <input type="hidden" name="_method" value="DELETE"/>
    <input type="submit" value="TestRest DELETE"/>
</form>

<form action="springmvc/testRest" method="post">
    <input type="submit" value="testRestPost">
</form>

<a href="springmvc/testRest/1">testRest</a>

The required filter is declared in web.xml:

<!-- Enable HiddenHttpMethodFilter to convert POST to DELETE/PUT -->
<filter>
    <filter-name>HiddenHttpMethodFilter</filter-name>
    <filter-class>org.springframework.web.filter.HiddenHttpMethodFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>HiddenHttpMethodFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

The @CookieValue annotation binds a specific cookie value to a method parameter, allowing easy access to cookies such as JSESSIONID.

@RequestMapping(value="/testCookieValue")
public String testCookieValue(@CookieValue("JSESSIONID") String cookieValue){
    System.out.println("testCookieValue: " + cookieValue);
    return SUCCESS;
}

A link like

<a href="springmvc/testCookieValue">testCookieValue</a>

triggers the method and prints the cookie value.

In summary, the article covers:

Usage of @RequestMapping for URL mapping.

Retrieving request data with @PathVariable and @RequestParam.

Implementing RESTful CRUD operations using HiddenHttpMethodFilter to simulate PUT and DELETE.

Accessing cookie values via @CookieValue.