HttpMediaTypeNotAcceptableException: Could not find acceptable representation spring mvc 4.1.5 with codehaus jackson 1.9.10

I am getting the error

org.springframework.web.HttpMediaTypeNotAcceptableException:: Could not find acceptable representation.

I think my project is configured properly to handle json restful requests. Are any more ideas on what else I should be doing differently?

I am using Spring MVC 4.1.5, jackson-mapper-asl-1.9.10.jar and jackson-core-asl-1.9.10.jar).

Here is my part of my web.xml

<!-- Creates the Spring Container shared by all Servlets and Filters -->
<listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

<!-- Processes application requests -->
<servlet>
    <servlet-name>appServlet</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>
            /WEB-INF/spring/appServlet/servlet-context.xml
        </param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
</servlet>

<servlet-mapping>
    <servlet-name>appServlet</servlet-name>
    <url-pattern>/</url-pattern>
</servlet-mapping>

Here is part of my servlet-context.xml

<!-- Handles HTTP GET requests for /resources/** by efficiently serving up static resources in the ${webappRoot}/resources directory -->
<resources mapping="/resources/**" location="/resources/" />

<!-- Resolves views selected for rendering by @Controllers to .jsp resources in the /WEB-INF/views directory -->
<beans:bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    <beans:property name="prefix" value="/WEB-INF/views/" />
    <beans:property name="suffix" value=".jsp" />
</beans:bean>

<context:component-scan base-package="com.losgatos">
    <context:include-filter type="annotation" expression="org.springframework.web.bind.annotation.ControllerAdvice" />
</context:component-scan>   

Here is my controller

package com.losgatos.controllers;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import com.losgatos.User;

@RestController
@RequestMapping( "user" )
public class UserController { 

    @RequestMapping( value = "data", produces="application/json" )
    public User getUser(){
        return new User();
    }   
}

Here is the User User POJO

package com.losgatos;

import java.util.EnumSet;

public class User {

    public User(){
        id = 0;
        age = 22;
        name = "Titus Feng"; 
        alias = "tornado tie";
        roles = EnumSet.of( Role.NORMAL, Role.NEW );
    }

    private int id, age;
    private String name, alias;
    private EnumSet<Role> roles;

    //added getters and setters here

    public enum Role{
        NEW, NORMAL, ADMIN, MEMBER, DORMANT 
    }   
}