网上查了资料，要显示 需要 在 layui.use 里面注册一下，然后 render 渲染
https://blog.csdn.net/light_666/article/details/80205041
<!DOCTYPE html>
<html lang="zh">
<html lang="zh" xmlns:th="http://www.w3.org/1999/xhtml">
<head>
<meta charset="UTF-8">
<meta name="renderer" content="webkit">
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1">
<link rel="stylesheet" href="//res.layui.com/layui/dist/css/layui.css" th:href="@{/css/layui/css/layui.css}" media="all">
<title>Title</title>
</head>
<body>
<!--图片上传页面-->
<section class="layui-main">
<fieldset class="layui-elem-field layui-field-title" style="margin-top: 30px;">
<legend>输入您要加入的新蛋糕内容，然后点击提交</legend>
</fieldset>
<form class="layui-form">
<div class="layui-form-item layui-form-text">
<label class="layui-form-label">蛋糕标题</label>
<div class="layui-input-block">
<textarea placeholder="请输入内容" class="layui-textarea"></textarea>
</div>
</div>
<div class="layui-form-item layui-form-text">
<label class="layui-form-label">主要内容</label>
<div class="layui-input-block">
<textarea placeholder="请输入内容" class="layui-textarea"></textarea>
</div>
</div>
<div class="layui-form-item layui-form-text">
<label class="layui-form-label">其他内容</label>
<div class="layui-input-block">
<textarea placeholder="请输入内容" class="layui-textarea"></textarea>
</div>
</div>
<div class="layui-form-item layui-form-text">
<label class="layui-form-label">主页标注[花费]</label>
<div class="layui-input-block">
<textarea placeholder="请输入内容" class="layui-textarea"></textarea>
</div>
</div>
<div class="layui-form-item layui-form-text">
<label class="layui-form-label">包装信息</label>
<div class="layui-input-block">
<textarea placeholder="请输入内容" class="layui-textarea"></textarea>
</div>
</div>
<div class="layui-form-item layui-form-text">
<label class="layui-form-label">材料信息</label>
<div class="layui-input-block">
<textarea placeholder="请输入内容" class="layui-textarea"></textarea>
</div>
</div>
<div class="layui-form-item">
<label class="layui-form-label">类别</label>
<div class="layui-input-inline">
<select name="quiz1" th:with="lists=${@cakeClassService.selectAllClassMap()}">
<option value="">选择一个类别吧</option>
<option th:each="map : ${lists}" th:text='${map.title}'
th:value='${map.class_id}'>
</option>
</select>
</div>
</div>
<div class="layui-form-item">
<div class="layui-input-block">
<button class="layui-btn" id="commit" onclick="return false">立即提交</button>
</div>
</div>
</form>
</section>
<script src="/static/build/layui.js" th:src="@{/css/layui/layui.js}"></script>
<script>
layui.use('form',function () {
let form = layui.form;
form.render();
})
</script>
</body>
</html>
