Using simple expression to get header value in spring xml

[Steve973]

Hello.  I am writing tests for my component with Spring, and configuring in
xml.  How can I specify these values so that it looks in the header,
instead of interpreting these as literal string values?

<endpoint id="subscribe-no-url-predicate"
uri="dynamic-router-control://subscribe">
    <property key="subscribeChannel" value="${headers.subscribeChannel}"/>
    <property key="subscriptionId" value="${headers.subscriptionId}"/>
    <property key="destinationUri" value="${headers.destinationUri}"/>
    <property key="priority" value="${headers.priority}"/>
</endpoint>

Thanks,
Steve