Using @RequestMapping(headers = "Accept=application/json") in SpringMVC4

Question

I am using Spring MVC 4 and I want to know that I am using @RestController at class level and for one of its method I am Using @RequestMapping(headers = "Accept=application/json"). Now can any one tell me why just by using <mvc:annotation-driven /> in my config-servlet.xml how I am getting the response in JSON on my browser. I mean using header attribute is only saying that this method can only respond to requests having this type of headers. How does the MVC4 knows to respond in JSON on browser. Here is my code:

My config-servlet.xml

<beans>
<context:component-scan base-package="com.songs.service.controller" />
<mvc:annotation-driven />
</beans>

My RestController Class

@RestController
@RequestMapping("/songappWS")
public class SongServiceWS 
{ 
@RequestMapping(value = "/topmoviesWS", method = RequestMethod.GET, headers="Accept=application/json")
public List<?> getTopMoviesWS() {
//method logic
return l1;

}
}

geoand · Accepted Answer · 2014-05-12 06:13:04Z

3

The reason Spring is responding in JSON is that @RestController implicitly means that the the response of getTopMoviesWS() method is handled as if it had the @ResponseBody annotation (already present in Spring 3).

What that means is that Spring will use the Jackson JSON library (if present on the classpath) to convert the response to JSON.

Check out this post.

edited May 12, 2014 at 6:13

answered May 12, 2014 at 6:07

geoand

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2 Comments

user3626306 Over a year ago

Is this like spring automatically chooses to return in JSON by default

geoand Over a year ago

When @ResponseBody is present or when using RestController and if Jackson is on the classpath, then yes, Spring MVC will return JSON

Centonni · Accepted Answer · 2014-05-13 12:31:26Z

3

You get the response in JSON because of @RestController, How??

@RestController is itself annotated with @Controller and @ResponseBody implying that @RequestMapping methods assume @ResponseBody semantics by default.You can have more information here.

To be more comprehensive, your code will look like this :

@RequestMapping(value = "/topmoviesWS", method = RequestMethod.GET, 
  headers="Accept=application/json")   
public @ResponseBody List<?> getTopMoviesWS() { 

   return l1;    
}

the @ResponseBody annotation on the getTopMoviesWS() method tells Spring MVC that it does not need to render the response through a server-side view layer, but that instead the list returned is the response body, and should be written out directly to the HTTP response as JSON. The list returned must be converted to JSON, you don’t need to do this conversion manually. Because Jackson 2 is on the classpath, Spring’s MappingJackson2HttpMessageConverter is automatically chosen to convert the values to JSON. You can have a look here to understand the @ResponseBody mechanism.

edited May 13, 2014 at 12:31

answered May 12, 2014 at 16:26

Centonni

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4 Comments

user3626306 Over a year ago

Thankyou.Now I know that by default spring chooses to return in JSON

Centonni Over a year ago

don't mention it :) I think you should close this topic by approving a answer or writing the right one and approve it.

user3626306 Over a year ago

can you answer this also stackoverflow.com/questions/23624909/…

user3626306 Over a year ago

Please answer to this question alsohttp://stackoverflow.com/questions/23644452/how-to-access-a-huge-json-coming-from-a-spring-restful-service-in-a-spring-mvc

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