判断list非空

<#if users?exists && users?size > 0 >
    <#list users as u>
        ${u.username}-----${u.password}
    </#list>
</#if>

判断对象非空

<#if user??>
    username:${user.username}
    password:${user.password}<br/>
    y001:${user.extending.y001}<br/>
    y002:${user.extending.y002}
</#if>

freemaker判断非空