Caused by: java.lang.IllegalArgumentException: Could not resolve placeholder

Caused by: java.lang.IllegalArgumentException: Could not resolve placeholder 'mail.host' in value "${mail.host}"

引用了两个properties配置。

<context:property-placeholder location="classpath:properties/jdbc.properties" ignore-unresolvable="true"/>

<context:property-placeholder location="classpath:properties/mail.properties" ignore-unresolvable="true"/>

都加上 ignore-unresolvable="true"