AJAX 响应不同于 java/hibernate 返回的字符串

AJAX response is different from java/hibernate returned string

这个简单的服务器端方法有一些问题 (java/hibernate):

@RequestMapping(value="/Prova" ,  method=RequestMethod.POST)
@Transactional( propagation = Propagation.REQUIRED, rollbackFor = Exception.class)
public ResponseEntity<String>  Prova(
        HttpServletRequest request, HttpServletResponse response
        ) throws Exception
{

    log.error("Sono qui");
    return new ResponseEntity<String>("pippotopolinopaperino",HttpStatus.OK);   

}

如果客户端发出 AJAX 请求(我使用 ExtJs),响应为:

pippotopolinopa0015↵

为什么?

P.s对不起我的英语不好

P.p.s 我也尝试过:

@RequestMapping(value="/Prova" ,  method=RequestMethod.POST)
@Transactional( propagation = Propagation.REQUIRED, rollbackFor = Exception.class)
public @ResponseBody  String   Prova(
        HttpServletRequest request, HttpServletResponse response
        ) throws Exception
{

    log.error("Sono qui");
    return "pippotopolinopaperino"; 

}

我是这样解决的:

@RequestMapping(value="/Prova" ,  method=RequestMethod.POST)
@Transactional( propagation = Propagation.REQUIRED, rollbackFor = Exception.class)
public @ResponseBody  List<String>   Prova(
    HttpServletRequest request, HttpServletResponse response
    ) throws Exception
{    
  log.error("Sono qui");
  List<String> ret = new ArrayList<String>();
  ret.add("pippoPlutoTopolino");
  return ret;        
}

或者:

@RequestMapping(value="/Prova2" ,  method=RequestMethod.POST)
@ResponseBody public StringBuffer Prova2(
        HttpServletRequest request
        ) throws Exception
{
  return new StringBuffer("pippoPlutoTopolino");  
}

但我不明白为什么不能返回一个简单的字符串。