java.io.File file = new java.io.File("/home/user/Source/starck-xsl/spec.json");
String jsonStr = org.apache.commons.io.FileUtils.readFileToString(file);

System.out.println(jsonStr);

org.json.JSONObject json = new org.json.JSONObject(jsonStr);
String xml = org.json.XML.toString(json);

System.out.println(xml);