弹簧引导:失败。。编写HTTP消息:springframework。http。转换器。HttpMessageNotWritableException

为了好玩,我正在编写一个简单的spring boot REST API。弹簧靴对我来说是新的。通过调用“/搜索”,我得到以下异常:

无法写入HTTP消息:org。springframework。http。转换器。HttpMessageNotWritableException:找不到类型为java类的返回值的转换器。util。LinkedHashMap

我的代码:

@后期映射(“/搜索”) public ResponseEntity getSearchResultViaAjax(@Valid@RequestBody SearchCriteria search,Errors Errors){

   ResponseBody result = new ResponseBody();

    //If error, just return a 400 bad request, along with the error message
    if (errors.hasErrors()) {

        result.setMsg(errors.getAllErrors().stream().map(x -> x.getDefaultMessage()).collect(Collectors.joining(",")));
        return ResponseEntity.badRequest().body(result);

    }

    List<User> users = userService.findByUserNameOrEmail(search.getUsername());
    if (users.isEmpty()) {
        result.setMsg("no user found!");
    } else {
        result.setMsg("success");
    }
    result.setResult(users);

    return ResponseEntity.ok(result);

}

任何帮助都将不胜感激。

提前感谢!