change return page to value

src/main/java/com/ctrip/fun/admin/controller/tools/CallCenterController.java

@@ -110,6 +110,7 @@ public class CallCenterController {
      * @return
      */
     @RequestMapping(value = "/callback", method = RequestMethod.POST)
+    @ResponseBody
     public String callbackEvent(HttpServletRequest request, HttpServletResponse response, @RequestBody String eventJsonString, ModelMap model) {
 		String result = "";