How to Use Spring RESTTemplate to Post Data to a Web Service

In this example, I am going to show you how to post data to a RESTful web service in Java using Spring, Spring Java Configuration and more.

Web Service Code

Let’s take a quick look at the Spring MVC Web Service code on the server:

@Controller
@RequestMapping("/api")
class JSonController
{

    private static final Logger logger = LoggerFactory.getLogger(JSonController.class);
    @RequestMapping(value = "/{id}", method = RequestMethod.POST)
    @ResponseBody
    public User updateCustomer(@PathVariable("id") String id, @RequestBody User user) {

        logger.debug("I am in the controller and got ID: " + id.toString());
        logger.debug("I am in the controller and got user name: " + user.toString());

        return new User("NEW123", "NEW SMITH");
    }

As you can see from the code above, the web service is going to wait for an ID and user object to be passed in and then it's going to create a new User Object and send it back to the client.

Let's take a quick look inside the User Object:

public class User
{
    private String user;
    private String name;
    public User()
    {
    }

    public User(String user, String name)
    {
        this.user = user;
        this.name = name;
    }

    public String getUser()
    {
        return user;
    }

    public void setUser(String user)
    {
        this.user = user;
    }

    public String getName()
    {
        return name;
    }

    public void setName(String name)
    {
        this.name = name;
    }
}

So you can see from the above code that the user object has two fields, user and name.

Time for the Client Code

You can see from the client code below that we are using Spring RESTTemplate and going to post a User Object to a web server and get one back.

@PropertySource("classpath:application.properties")
public class Main
{

    /**
     * Setting up logger
     */
    private static final Logger LOGGER = getLogger(Main.class);
    public static void main(String[] args) throws IOException
    {
        LOGGER.debug("Starting REST Client!!!!");

        /**
         *
         * This is going to setup the REST server configuration in the applicationContext
         * you can see that I am using the new Spring's Java Configuration style and not some OLD XML file
         *
         */
        ApplicationContext context = new AnnotationConfigApplicationContext(RESTConfiguration.class);

        /**
         *
         * We now get a RESTServer bean from the ApplicationContext which has all the data we need to
         * log into the REST service with.
         *
         */
        RESTServer mRESTServer = context.getBean(RESTServer.class);
        /**
         *
         * Setting up data to be sent to REST service
         *
         */
        Map<String, String> vars = new HashMap<String, String>();
        vars.put("id", "JS01");
        /**
         *
         * Doing the REST call and then displaying the data/user object
         *
         */
        try
        {

            /*

                This is code to post and return a user object

             */

            RestTemplate rt = new RestTemplate();
            rt.getMessageConverters().add(new MappingJacksonHttpMessageConverter());
            rt.getMessageConverters().add(new StringHttpMessageConverter());

            String uri = new String("http://" + mRESTServer.getHost() + ":8080/springmvc-resttemplate-test/api/{id}");

            User u = new User();
            u.setName("Johnathan M Smith");
            u.setUser("JS01");

            User returns = rt.postForObject(uri, u, User.class, vars);

            LOGGER.debug("User:  " + u.toString());

        }
        catch (HttpClientErrorException e)
        {
            /**
             *
             * If we get a HTTP Exception display the error message
             */

            LOGGER.error("error:  " + e.getResponseBodyAsString());

            ObjectMapper mapper = new ObjectMapper();
            ErrorHolder eh = mapper.readValue(e.getResponseBodyAsString(), ErrorHolder.class);

            LOGGER.error("error:  " + eh.getErrorMessage());

        }
        catch(Exception e)
        {
            LOGGER.error("error:  " + e.getMessage());

        }
    }

}

You can see from the above code how easy it is to use RESTTeample to post data to a web service.

Where Can I Get the Source Code?

You can check out the project on GitHub.

git clone git@github.com:JohnathanMarkSmith/springmvc-resttemplate-test.git
cd springmvc-resttemplate-test.git