Spring Integration: Mail error and HTTP gateway response - email

Question

My use case is simple. I want to handle an exception caused by a system being unreachable, perform a retry based upon a configured retry policy, send an email when the retry threshold has been met, and return a custom response back the caller.
The challenges I am facing is that I cannot both send an email and return a response back to the caller. Since I was using a int-mail:outbound-channel-adapter initially, I would expect this behavior since this is a one-way component:
<int:chain input-channel="defaultErrorChannel">
<int:service-activator id="mailMessageActivator" expression="#mailHandler.process(payload)" />
<int-mail:outbound-channel-adapter mail-sender="mailSender" />
</int:chain>
However, if I introduce a int-amqp:outbound-gateway in front of the int-mail:outbound-channel-adapter (see the Error Handling config below), I would expect to be able to invoke a int:service-activator to construct and return a response to the caller.
Am I thinking about this the wrong way? I see that someone else had a similar question which is still unanswered. Both of the configurations I mentioned send emails, but always block from the caller without receiving a response upon timeout.
Here are the relevant parts of my configuration:
Gateway
<int:gateway id="customerGateway" service-interface="com.uscs.crm.integration.CustomerGateway"
default-request-channel="syncCustomers" default-reply-channel="replySyncCustomers" default-reply-timeout="30000">
</int:gateway>
<int:object-to-json-transformer input-channel="syncCustomers" output-channel="outboundRequestChannel" />
<int-http:outbound-gateway request-channel="outboundRequestChannel" reply-channel="replySyncCustomers"
url="http://voorhees148.uscold.com:9595/web/customerSync/createCustomer"
http-method="POST"
rest-template="restTemplate"
expected-response-type="com.uscs.crm.model.CustSyncResponseVO"
mapped-request-headers="Authorization, HTTP_REQUEST_HEADERS">
<int-http:request-handler-advice-chain>
<ref bean="retryWithBackoffAdviceSession" />
</int-http:request-handler-advice-chain>
</int-http:outbound-gateway>
Error Handling
<int:channel id="defaultErrorChannel"/>
<int:channel id="errorResponses"/>
<!--
ExponentialBackOffPolicy.multipler is applied to wait time over each retry attempt
with a ExponentialBackOffPolicy.maximum configured.
-->
<bean id="retryWithBackoffAdviceSession" class="org.springframework.integration.handler.advice.RequestHandlerRetryAdvice">
<property name="retryTemplate">
<bean class="org.springframework.retry.support.RetryTemplate">
<property name="backOffPolicy">
<bean class="org.springframework.retry.backoff.ExponentialBackOffPolicy">
<property name="initialInterval" value="2000" />
<property name="multiplier" value="2" />
<property name="maxInterval" value="30000"/>
</bean>
</property>
<property name="retryPolicy">
<bean class="org.springframework.retry.policy.SimpleRetryPolicy">
<property name="maxAttempts" value="3"/>
</bean>
</property>
</bean>
</property>
<property name="recoveryCallback">
<bean class="org.springframework.integration.handler.advice.ErrorMessageSendingRecoverer">
<constructor-arg ref="defaultErrorChannel"/>
</bean>
</property>
</bean>
<bean id="custSyncResponseHandler" class="com.uscs.crm.integration.handler.CustSyncResponseHandler"></bean>
<int:chain input-channel="defaultErrorChannel" output-channel="replySyncCustomers">
<int:service-activator id="mailMessageActivator" expression="#mailHandler.process(payload)" />
<int:header-enricher>
<int:header name="ERROR_ID" expression="T(java.lang.System).currentTimeMillis()"/>
</int:header-enricher>
<int-amqp:outbound-gateway
exchange-name="error-responses-exchange"
routing-key-expression="'error.response.'+headers.ERROR_ID"
amqp-template="amqpTemplate" />
<!-- Will this service-activator return a response to the caller (int:gateway) using channel `replySyncCustomers`? -->
<int:service-activator id="custSyncResponseActivator" expression="#custSyncResponseHandler.process(payload)" />
</int:chain>
<int-amqp:inbound-gateway queue-names="error-responses" request-channel="errorResponses"
connection-factory="rabbitConnectionFactory" acknowledge-mode="AUTO" />
<int-mail:outbound-channel-adapter channel="errorResponses" mail-sender="mailSender" />
<!-- (Outbound Channel Adapter/Gateway) rabbit exchanges, queues, and bindings used by this app -->
<rabbit:topic-exchange name="error-responses-exchange" auto-delete="false" durable="true">
<rabbit:bindings>
<rabbit:binding queue="error-responses" pattern="error.response.*"/>
</rabbit:bindings>
</rabbit:topic-exchange>
<rabbit:queue name="error-responses" auto-delete="false" durable="true"/>
SOLUTION: I was able to get this working with help from #Artem. Below are the changes I made.
Service Activator Implementation (handling ErrorMessage)
The key is the line which returns the reconstructed Message with all of the header information from the ErrorMessage.
#Override
public Message<CustSyncResponseVO> process(Message<MessagingException> errorMessage) {
MessagingException errorException = errorMessage.getPayload();
CustSyncResponseVO custSyncResponse = new CustSyncResponseVO();
custSyncResponse.setResponseMessage(ExceptionUtils
.convertToString(errorMessage.getPayload()));
return MessageBuilder.withPayload(custSyncResponse)
.copyHeaders(errorMessage.getHeaders())
.copyHeadersIfAbsent(errorException.getFailedMessage().getHeaders()).build();
}
Service Activator Config
Used SpEL to reference the #root context to retrieve the ErrorMessage instead of the default which would be MessagingException (payload) and passed it to my process method on the POJO.
<bean id="custSyncResponseHandler" class="com.uscs.crm.integration.handler.CustSyncResponseHandler" />
<int:chain id="errorGatewayResponseChain" input-channel="defaultErrorChannel" output-channel="replySyncCustomers">
<int:service-activator id="custSyncResponseActivator" expression="#custSyncResponseHandler.process(#root)" />
</int:chain>

Answer 1

I don't see reason to introduce the AMQP middleware complexity there just for sending email in the end.
What only you need is <publish-subscribe-channel id="defaultErrorChannel"> with to endpoints as subscribers to it.
The first one is one-way email sending <chain> and the second one is custSyncResponseActivator to reply something to your <int-http:outbound-gateway>.
You can find more info on the matter in the Spring Integration Reference Manual.