<int-http:outbound-gateway id="httpOutboundGateway" request-channel="fromMyQueue"
    url="{outboundGatewayUrl}" reply-channel="nullChannel"
    http-method="POST" expected-response-type="java.lang.String" charset="UTF-8">
<int-http:uri-variable name="outboundGatewayUrl" expression="headers['X-CUSTOM-HTTP-REQUEST-URL']" />

Caused by:
org.springframework.integration.MessageHandlingException: HTTP request execution failed for URI [{outboundGatewayUrl}]...

Caused by:<br> java.lang.IllegalArgumentException: URI is not absolute
    at java.net.URI.toURL(URI.java:1080)
    at org.springframework.http.client.SimpleClientHttpRequestFactory.createRequest(SimpleClientHttpRequestFactory.java:109)

<int-http:uri-variable name="outboundGatewayUrl" expression="'http://foo/bar'" />

Caused by:
org.springframework.integration.MessageHandlingException: HTTP request execution failed    for URI [{outboundGatewayUrl}]...