How to use logging-channel-adapter in Spring Integration to log a message header value

Question

I need to log the value of the message header with key "foo_bar" so that the log message looks something like this when the value of that header is "baz":

Value of header foo_bar: baz

How to do this with a wire-tap and logging-channel-adapter?

Solution

Use the expression attribute of the logging-channel-adapter and set up the wire-tap and logging-channel-adapter something like this:

<integration:channel id="channel1">
    <integration:interceptors>
        <integration:wire-tap channel="loggingChannel1"/>
    </integration:interceptors>
</integration:channel>
<integration:logging-channel-adapter 
    id="loggingChannel1" 
    expression="'Value of header foo_bar: '.concat(headers.foo_bar)" 
    level="DEBUG"
/>

When using the expression attribute, the root object is the spring integration message. So "headers" in the expression gets you the headers map of the message.