ftl页面报错The only legal comparisons are between two numbers, two strings, or two dates

ftl页面报错The only legal comparisons are between two numbers, two strings, or two dates

在freemarker的ftl页面中if标签常常会报freemarker.template.TemplateException: The only legal comparisons are between two numbers, two strings, or two dates.的错误。

例如

<#if 1=="${1?if_exists?html}"></#if>这句话就会报错，因为1是int类型，"${1?if_exists?html}"是字符串，不同类型比较失败。

解决方法：把int类型转成字符串即可。修改如下：

<#if "1"=="${1?if_exists?html}"></#if>

或

<#if "${1?if_exists?html}"=="${1?if_exists?html}"></#if>