Spring MVC preparing JSON but loading a page instead - json

Question

I have a controller to send back a JSON Payload
#RequestMapping(value = "/MerchantMonitoringAPI", method = RequestMethod.GET,produces = "application/json")
public String MerchantMonitoring() {
ApplicationContext context =
new ClassPathXmlApplicationContext("Spring-Module.xml");
TopMerchantsDAO topMerchantsDAO = (TopMerchantsDAO) context.getBean("topMerchantsDAO");
TopMerchants topMerchants = topMerchantsDAO.retrieveMerchantList();
for(String temp:topMerchants.getMerchantList())
{
System.out.println(temp);
}
Gson gson = new Gson();
Type type = new TypeToken<TopMerchants>() {}.getType();
String jsonPayload = gson.toJson(topMerchants, type);
System.out.println(jsonPayload);
return jsonPayload;
}
It is trying to redirect me to a view with the page name as the JSON (localhost:8080/{"merchantList":["Apple","Google"]}.jsp)
How to stop this and return the JSON payload ??

Answer 1

Add #RestController on top of the #RequestMapping
#RestController
#RequestMapping(value = "/MerchantMonitoringAPI", method =
RequestMethod.GET,produces = "application/json")
public String MerchantMonitoring() {...}
Because the method is now annotated with #RestController, the objects returned from this methods will go through message conversion to produce a json resource representation for the client.

Answer 2

If you want to have several methods for returning JSON and page in the same class, you can still annotate your class with #Controller, and the method for JSON annotated with #ResponseBody
If you will annotated class with #RestController - all methods inside class will be working like #ResponseBody and class will be like #Controller annotated. Of course, this is a better approach (to not include page and JSON returning methods in one Controller).
Notice! You can use #RestController only for class (instead of #Controller), not for methods.
If you will open source of this annotation, you will see among other things the next:
#Target({ElementType.TYPE})
#Retention(RetentionPolicy.RUNTIME)
#Documented
#Controller
#ResponseBody
public #interface RestController {
String value() default "";
}
and ElementType.TYPE has comment:
Class, interface (including annotation type), or enum declaration