java8，Optional实际开发应用案例

  Optional，一个支持函数式编程的判空容器。最近开发简单应用了一下,代码贴上~

    @RequestMapping(value = "/list", method = RequestMethod.GET)
    public Result> queryPageList(SysUser sysUser, @RequestParam(name = "pageNo", defaultValue = "1") Integer pageNo,
                                                @RequestParam(name = "pageSize", defaultValue = "10") Integer pageSize, HttpServletRequest req) {
        Result> result = new Result<>();
        QueryWrapper queryWrapper = QueryGenerator.initQueryWrapper(sysUser, req.getParameterMap());
        Page page = new Page(pageNo, pageSize);
        IPage pageList = sysUserService.page(page, queryWrapper);
        pageList.getRecords().forEach(item -> {
            List listRoleNames = new ArrayList<>();
            QueryWrapper wrapper = new QueryWrapper<>();
            wrapper.eq("user_id", item.getId());
            List listSysUserRoles = sysUserRoleService.list(wrapper);
            List listRoleIds = listSysUserRoles.stream()
                    .map(SysUserRole::getRoleId)
                    .collect(Collectors.toList());
            if (!listRoleIds.isEmpty()) {
                List sysRoles = sysRoleService.getbaseMapper().selectBatchIds(listRoleIds);
                sysRoles.forEach(item1 -> {
                                // Optional 应用案例
                                listRoleNames.add(Optional.ofNullable(item1).map(SysRole::getRoleName).orElse(null));
                });
            }
            item.setRoleName(listRoleNames);
        });
        result.setSuccess(true);
        result.setResult(pageList);
        return result;
    }