response body is empty after write log for body - jbossfuse

Question

I am testing fuse63 on spring dsl for rest service, I need to proxy a rest service on camel for back end system, here is excerpt:
<camelContext id="_camelContext1_rest" xmlns="http://camel.apache.org/schema/spring">
<restConfiguration component="spark-rest" port="9091"/>
<rest path="/say">
<post consumes="application/json" produces="text/plain" uri="/hellopost">
<to uri="direct:hellopost"/>
</post>
...
<route id="_route_saypost">
<from id="_from_saypost" uri="direct:hellopost"/>
<log id="_log_saypost" message="this is hellopost"/>
<to id="_file_saypost" uri="file:/tmp2/target/messages/hellopost?fileName=${header.fileName}"/>
<setHeader headerName="camel-test" id="_setHeader1">
<constant>this is camel</constant>
</setHeader>
<setHeader headerName="CamelHttpMethod" id="_setHeader2">
<constant>POST</constant>
</setHeader>
<log id="_log_saypost_before_rest" message="before rest"/>
<to id="_to1" uri="http4://192.168.56.11:8080/test/httpheader.jsp?bridgeEndpoint=true&synchronous=true"/>
<setHeader headerName="Content-Type" id="_setHeader2">
<constant>application/json</constant>
</setHeader>
</route>
This works fine, but if I add the logging action at the end of the route:
<log id="_log_saypost_after_rest3" message="${body}"/>
</route>
the response body from camel(localhost:9091/say/hellopost) will be empty, What's the reason for the response body being cleared after a logging action?
Best regards
Lan

Answer 1

Use Stream caching like
<route streamCache="true">
This http://camel.apache.org/why-is-my-message-body-empty.html answers to your question.

Answer 2

In fact you don't have to use directy
<log />
but you have to use
<to uri="log: "/>
https://camel.apache.org/components/3.15.x/log-component.html