要检查该值是否存在：
[#if userName??] Hi ${userName}, How are you?[/#if]或使用标准的freemarker语法：
<#if userName??> Hi ${userName}, How are you?</#if>要检查该值是否存在并且不为空：
<#if userName?has_content> Hi ${userName}, How are you?</#if>
要检查该值是否存在：
[#if userName??] Hi ${userName}, How are you?[/#if]或使用标准的freemarker语法：
<#if userName??> Hi ${userName}, How are you?</#if>要检查该值是否存在并且不为空：
<#if userName?has_content> Hi ${userName}, How are you?</#if>名师互学网 版权所有 (c)2021-2022 ICP备案号：晋ICP备2021003244-6号
