How can we send orbeon form data in JSON format?

As of now I am sending my form data to external web services for perform some business logic with form data as XML format. I want to send my form data in JSON format instead XML format. IS this possible? In the documentation I am able to see only three options (xml,metadata,pdfurl). How can I send the form data in JSON format?

<property
  as="xs:string"
  name="oxf.fr.detail.process.send.*.*"
  value='require-valid
         then send(uri = "http://localhost:9090/ServletAction/demoClass", method="POST", content="metadata")
         then navigate("http://localhost:8080/orbeon/xforms-jsp/guess-the-number/index.jsp")
         recover navigate("http://localhost:8080/orbeon/xforms-jsp/flickr-search/index.jsp")'/>

Any suggestion?