Thymeleaf生成pdf表格合并单元格描边不显示

生成pdf后左侧第一列的右描边不显示，但是html显示正常

显示异常时描边的写法

cellpadding=“0” cellspacing=“0” ，td,th描边

        .self-table{border:1px solid #000;border-collapse: collapse;width:100%}.self-table th{font-size:12px;border:1px solid #000!important;font-family: heiti;}.self-table td{font-size:10px;border:1px solid #000!important;font-family: songti;}

<table class="self-table" cellpadding="0" cellspacing="0">
</table>

修改描边写法后，显示正常

cellpadding=“0” cellspacing=“1px”，表格背景为黑色，th,td背景为白色。

        .self-table{width:100%;background:#000;}.self-table th{font-size:12px;font-family: heiti;background:#fff;padding:3px 0;}.self-table td{font-size:10px;font-family: songti;background:#fff;}

<table class="self-table" cellpadding="0" cellspacing="1px">
</table>

生成的pdf表格显示正常截图