You have to register the annotation binding for Jackson in your spring-mvc-config.xml, for example :
<!-- activates annotation driven binding -->
<mvc:annotation-driven ignoreDefaultModelOnRedirect="true" validator="validator">
<mvc:message-converters>
<bean class="org.springframework.http.converter.ResourceHttpMessageConverter"/>
<bean class="org.springframework.http.converter.xml.Jaxb2RootElementHttpMessageConverter"/>
<bean class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter"/>
</mvc:message-converters>
</mvc:annotation-driven>
Then in your controller you can use :
@RequestMapping(value = "/your_url", method = RequestMethod.GET, produces = "application/json")
@ResponseBody