Using QueueChannel in Spring Integration - spring-integration

Question

I am working on the below case study.
Create a Rest Service to accept Reference id.
Use the Reference Id to get data (CLOB) from Database.
Put the data(CLOB) in a channel(queue) for further processing.
Reply to the rest client with response data in JSON format {"status": true,"message": "RECEIVED"}
I have the Rest Service created and using the Ref Id am getting the data from database but I am unable to send the response back to the rest client after putting the message in a channel(queue).
The output received by Rest Client is : No reply received within timeout
Basically I want the request thread to be returned immediately after the data (CLOB) is pushed to the channel(queue).
Below is the configuration.
<int:channel id="responseChannel"/>
<int:channel id="initCalculation">
<int:queue/>
</int:channel>
<!-- GET -->
<int-http:inbound-gateway
request-channel="httpGetChannel"
reply-channel="responseChannel"
supported-methods="GET"
path="/init/{refId}"
payload-expression="#pathVariables.refId">
<int-http:request-mapping produces="application/json"/>
</int-http:inbound-gateway>
<int:chain input-channel="httpGetChannel" output-channel="initCalculation">
<int-jdbc:stored-proc-outbound-gateway
id="outbound-gateway-storedproc-get-forma" data-source="dataSource"
is-function="false"
stored-procedure-name="XX_EMPROC.GET_FRMA"
ignore-column-meta-data="true"
expect-single-result="true">
<int-jdbc:sql-parameter-definition name="V_REF_ID" direction="IN" />
<int-jdbc:sql-parameter-definition name="V_FRMA" direction="OUT" type="#{T(oracle.jdbc.OracleTypes).CLOB}"/>
<int-jdbc:parameter name="V_REF_ID" expression="payload" />
</int-jdbc:stored-proc-outbound-gateway>
<!- Convert to JSON Format -->
<int:service-activator ref="brInitGateway" method="getResponse"/>
</int:chain>
<int:outbound-channel-adapter channel="initCalculation" ref="brInitGateway" method="process"/>
Kindly advise on the corrections needed in the above.
Thanks

Answer 1

Look, there is no body who sends message as a reply to the <int-http:inbound-gateway>. You have declared responseChannel, but who is going to use it as an output-channel?
I'd suggest you to do this:
<publish-subscribe-channel id="responseChannel"/>
<int:chain input-channel="httpGetChannel" output-channel="responseChannel">
<int:bridge input-channel="responseChannel" output-channel="initCalculation"/>
So, what happens here:
The publish-subscribe-channel for the reply-channel makes an internal bridge to the replyChannel header as one of the subscribers.
You send a result from the <chain> to that channel. Therefore the <int-http:inbound-gateway> gets its reply.
Having that <int:bridge> from response to the initCalculation you have a second subscriber and, therefore, send a message to the required queue.
If you are not interested in the brInitGateway.getResponse() as a reply for the HTTP request, you should consider do not have that reply-channel="responseChannel" at all, but still use some <publish-subscribe-channel> to send to the queue and some transformer to prepare a reply, e.g.:
<transformer input-channel="prepareProcess" expression="' {"status": true,"message": "RECEIVED"}'"/>
This transformer is without output-channel because it is going to send its result into the replyChannel header, therefore to the <int-http:inbound-gateway> initiator.