thymeleaf判断对象是否为空的相关逻辑处理

@RequestMapping(path = { 
   "/add", "edit"}, method = { 
   RequestMethod.GET})
public String addOrEdit(Model model, @RequestParam(name = "postId", required = false) Long postId) { 
   
    if (!StringUtils.isEmpty(postId)) { 
   
            UserLoginResult userLoginResult = (UserLoginResult) SecurityUtils.getSubject().getPrincipal();
            PostVO postVO = postService.findOnePostVO(postId);
            Assert.isTrue(postVO != null, "该帖子已被删除");
            Assert.isTrue(postVO.getUserId().longValue() == userLoginResult.getId().longValue(), "没有权限操作");
            model.addAttribute("post", postVO);
        }
        List<Category> categoryList = categoryService.findCategoryAllOfName();
        model.addAttribute("list", categoryList);
        return "jie/add";
    }
}

<!-- 正确写法可以实现 -->
<li class="layui-this" th:text="${post != null?'编辑页面':'添加页面'}"></li>

<!-- 无法实现 -->
<li class="layui-this" th:text="${post} ne 'null'?'编辑页面':'添加页面'"></li>

<div class="layui-input-block">
	<select lay-verify="required" name="categoryId" lay-filter="column">
    	<option></option>
    	<!-- 此处遍历 -->
        <option th:each="category:${categoryList}" th:value="${category.id}" th:text="${category.categoryName}" <!-- 加了这个 ‘？’ 用于判断 -->
            th:selected="${category.id} == ${post?.categoryId}">
        </option>
    </select>
</div>