Please make sure that you have the following in your Spring xml file:
<context:annotation-config/>
<bean id="jacksonMessageConverter" class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter"></bean>
<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
<property name="messageConverters">
<list>
<ref bean="jacksonMessageConverter"/>
</list>
</property>
</bean>
and all items of your POJO should have getters/setters.
Hope it helps