How to get Spring MVC output using XStream to convert JSON to XML

Question

I have a web application using Spring MVC (3.0.5) that outputs JSON using the HttpMessageConverter when the application/json is passed in Accept header. I want to output XML using XStream, but instead of the underlying Java object, I want to use the JSON representation that I've already customized.

My spring configuration looks like

<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
  <property name="messageConverters">
    <list>
      <bean class="org.springframework.http.converter.ByteArrayHttpMessageConverter" />
      <bean class="org.springframework.http.converter.StringHttpMessageConverter" />
      <bean class="org.springframework.http.converter.FormHttpMessageConverter" />
      <bean class="org.springframework.http.converter.xml.SourceHttpMessageConverter" />
      <bean class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter" />
    </list>
  </property>
</bean>

I can add another XStreamMashaller and get the XML output from the Java Object, but that's a different representation and I don't want to make the effort in syncing the two representations. I want to use the JSON representation to be converted to XML using something like Jettison. Can somebody guide me to a link or some example code on how this can be achieved?