Correct JSON REST Controller by Spring

Question

I am new in writing spring rest controller. I want to create a simple sending in JSON format, but I can't deal with it, is my code a correct code for it?

In my code, there is a RestTemplate, which sends a simple POJO to the REST url, and the REST Controller sends back another POJO.

I found a lot of examples sending and receiving objects as JSON, but some of them are a few years old. The most I found is where they configure the dispatcher bean XML by adding MappingJackson2HttpMessageConverter for Configure bean to convert JSON to POJO and vice versa :

...
<beans:bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
    <beans:property name="messageConverters">
        <beans:list>
            <beans:ref bean="jsonMessageConverter"/>
        </beans:list>
    </beans:property>
</beans:bean>
<beans:bean id="jsonMessageConverter" class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
</beans:bean> 
...

And also they set it to the RestTemplate java code:

List<HttpMessageConverter<?>> messageConverters = new ArrayList<HttpMessageConverter<?>>();
messageConverters.add(new MappingJackson2HttpMessageConverter());
messageConverters.add(new StringHttpMessageConverter());
restTemplate.setMessageConverters(messageConverters);

Sometimes they set a header too:

HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON);
headers.add("Accept", "application/json");
HttpEntity<MyObject> entity = new HttpEntity<MyObject>(inputRequest, headers);

Sometimes they convert their object to JSON format, and send it as a text, not the instance.

And also I can found 2 ways for sending a POST message:

ResponseEntity<MyObject> responseEntity = restTemplate.exchange(url, HttpMethod.POST, entity, MyObject.class);

or

MyObject response = restTemplate.postForObject(url, inputRequest, MyObject.class);

And this is the REST Controller:

@RequestMapping(value = "/send", method = RequestMethod.POST, consumes=MediaType.APPLICATION_JSON_VALUE, produces=MediaType.APPLICATION_JSON_VALUE)
@ResponseBody
public MyObject send(@RequestBody MyObject requestModel) {
    return //whatever;
}

BUT: if I don't set anything into the XML, and don't add any message converter and header to the RestTemplate, it looks like it working fine. I test it by PostMan, and if I add a JSON format of my MyClass example, I receive JSON.

So my question is: Is my code correct this way for JSON sending really?:

mvc-dispatcher.xml:

<?xml version="1.0" encoding="UTF-8"?>
<beans:beans xmlns="http://www.springframework.org/schema/mvc"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:beans="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">
    <!-- Enables the Spring MVC @Controller programming model -->
    <annotation-driven />
    <!-- to reach resources like css and images -->
    <default-servlet-handler/>
    <!-- the REST controllers are here -->
    <context:component-scan base-package="hu.viktor" />
</beans:beans>

RestTemplate java:

@Controller
public class RequestSender {
    public MyObject send(MyObject inputRequest) {
        RestTemplate restTemplate = new RestTemplate();
        String url = "http://localhost:8080/rest/send";
        MyObject response = restTemplate.postForObject(url, inputRequest, MyObject.class);
        return response;
    }
}

And the REST Controller:

@Controller
@RequestMapping("/rest")
public class CalculatorRestController {
    @RequestMapping(value = "/send", method = RequestMethod.POST, consumes=MediaType.APPLICATION_JSON_VALUE, produces=MediaType.APPLICATION_JSON_VALUE)
    @ResponseBody
    public MyObject send(@RequestBody MyObject requestModel) {
        return //whatever;
    }   
}

Answer 1

According to documentation RequestMappingHandlerMapping and RequestMappingHandlerAdapter will be added automatically, if you specified <mvc:annotation-driven/> in xml configuration (in your case just <annotation-driven> ). The same documentation contains the list of HttpMessageConverters , which will be set up by <mvc:annotation-driven>' . And:

MappingJackson2HttpMessageConverter converts to/from JSON — added if Jackson 2 is present on the classpath.

This means, that you don't need to add json message converter manually, just specify <mvc:annotation-driven> in configuration file and declare dependencies in your pom.xml (if you're using Maven):

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-core</artifactId>
    <version>2.4.6</version>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.4.6.1</version>
</dependency>