Thursday, 8 November 2012

Spring MVC REST Calls With HTTP Only

This post describes how to perform REST calls to a Spring MVC application using HTTP only. This example is a variation of the Spring MVC REST Calls With Ajax example. The code is available on GitHub in the Spring-REST-With-HTML-Only directory.

Web.xml

We need to add the HiddenHttpMethodFilter to our web.xml. It searches HTML form PUTs for a _method parameter. If the corresponding value is GET, PUT, POST or DELETE, the call is transformed into a REST call before it is transmitted to the controllers:
...
<servlet-mapping>
    <servlet-name>MyServlet</servlet-name>
    <url-pattern>/</url-pattern>
</servlet-mapping>

<filter>
    <filter-name>hiddenHttpMethodFilter</filter-name>
    <filter-class>org.springframework.web.filter.HiddenHttpMethodFilter</filter-class>
</filter>

<filter-mapping>
    <filter-name>hiddenHttpMethodFilter</filter-name>
    <servlet-name>MyServlet</servlet-name>
</filter-mapping>
...

Main Page

We replace the buttons by HTML post forms:
<%@page contentType="text/html" pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!doctype html>
<html lang="en">
<head>
  <meta http-equiv="Content-Type" content="text/html;" charset=UTF-8">
  <title>Welcome To REST With HTML Only !!!</title>
</head>
<body>
    <h1>Welcome To REST With HTML Only !!!</h1>
    <form action="<c:url value='/MyData/123466/'/>"
          method="post" >
        <input type="hidden" name="_method" value="GET">
        <input type="submit" value="GET">
    </form>
    <form action="<c:url value='/MyData'/>"
          method="post" >
        <input type="hidden" name="time" value="555555">
        <input type="hidden" name="message" value="User PUT call !!!">
        <input type="hidden" name="_method" value="PUT">
        <input type="submit" value="PUT">
    </form>
    <form action="<c:url value='/MyData'/>"
          method="post" >
        <input type="submit" value="POST">
    </form>
    <form action="<c:url value='/MyData/654321'/>"
          method="post" >
        <input type="hidden" name="_method" value="DELETE">
        <input type="submit" value="DELETE">
    </form>
</body>
</html>

Controller

We need to modify our controller for PUT calls:
@Controller
@RequestMapping(value = "/MyData")
public class MyRESTController {

    @RequestMapping(value="/{time}", method = RequestMethod.GET)
    public @ResponseBody MyData getMyData(
            @PathVariable long time) {

        return new MyData(time, "REST GET Call !!!");
    }

    @RequestMapping(method = RequestMethod.PUT)
    public @ResponseBody MyData putMyData(
            @RequestParam("time") long time,
            @RequestParam("message") String message) {

        return new MyData(time, message);
    }

    @RequestMapping(method = RequestMethod.POST)
    public @ResponseBody MyData postMyData() {
        return new MyData(
            System.currentTimeMillis(), "REST POST Call !!!");
    }

    @RequestMapping(value="/{time}", method = RequestMethod.DELETE)
    public @ResponseBody MyData deleteMyData(
            @PathVariable long time) {

        return new MyData(time, "REST DELETE Call !!!");
    }

}

Running The Example

Once compiled, the example can be run with mvn tomcat:run. Then, browse:

  http://localhost:8585/spring-rest-with-html-only

The main page will be displayed:

Spring MVC REST Calls With HTML Only


If you click on a button, the corresponding JSON will be displayed:

Spring MVC With HTML Only JSON
More Spring related posts here.