前端js与服务器联调出现的sessionId变更的问题

场景：前端搭建本地服务器，访问我的本地服务器接口　进行联调；

服务器代码：

@RequestMapping(value = "/login", method = RequestMethod.POST)
@ResponseBody
public CSResponse login(HttpServletRequest request, @RequestBody LoginRequest loginBean) {
    String workId = loginBean.getUserNum();
    String password = loginBean.getPassword();
    if (StringUtils.isBlank(workId) || StringUtils.isBlank(password)) {
        //用户名或密码为空
        throw new ErrorCodeException(ErrorEnum.CONFIRM_PASSWORD_WRONG);
    }
    UserEntity user = userService.login(workId, password);
    if (null != user) {
        HttpSession session = request.getSession();
        session.setAttribute(CSContents.USER_SESSION, user);
        UserModelVO userModelVO = UserModelConverter.initUserModelIVOValues(user);
        CSResponse loginResponse = new CSResponse();
        loginResponse.setDetailInfo(userModelVO);
        return loginResponse;
    } else {
        throw new ErrorCodeException(ErrorEnum.USER_NOT_EXITS);
    }
}

/**
 * 用户获取接口
 *
 * @param request
 * @return
 */
@RequestMapping(value = "/getUserSession", method = RequestMethod.GET)
@ResponseBody
public CSResponse getUserSession(HttpServletRequest request) {
    UserEntity user = (UserEntity) request.getSession().getAttribute(CSContents.USER_SESSION);
    CSResponse loginResponse = new CSResponse();
    if (null != user) {
        UserModelVO userModelVO = UserModelConverter.initUserModelIVOValues(user);
        loginResponse.setDetailInfo(userModelVO);
        return loginResponse;
    } else {
        return loginResponse;
    }
}

前端调用getUserSession接口刷新后获取不到session里面的值，经过debug发现session的ＩＤ发生变更；

为了排除原因，在一台服务器上进行操作，前端将代码长传到仓库对应的路径，结果发现ｓｅｓｓｉｏｎＩＤ没有发生变更，由此可见是由于跨域请求出现的问题；

解决方案：前端加上一下代码片段（crossDomain:true 属性）：

$.ajax({
    type: (!_method ? "post" : _method),
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    url: _url,
    async: true,
    crossDomain: true,
    data: JSON.stringify(_data),
    success: function (data) {
        if (data.code == 0) {
            _callback(data);
        } else {
            alert(data.desc);
        }
    }
});