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https://issues.apache.org/activemq/browse/CAMEL-1366?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=50050#action_50050
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Michael Chen commented on CAMEL-1366:
-------------------------------------
Actually, the logic in EndpointMessageListener.createExchange() made it
impossible. If disableReplyTo is set to true, the
"org.apache.camel.jms.replyDestination" will not be set. Downstream processor
will have no way to know how to reply.
Since we have talked about it, I want to *reinstate* the original change
suggestion *plus* the following. In the createExchange() method, these lines:
{code}//
if (replyDestination != null && !disableReplyTo) {
exchange.setProperty("org.apache.camel.jms.replyDestination",
replyDestination);
exchange.setPattern(ExchangePattern.InOut);
}
{code}
should be changed to:
{code}//
if (replyDestination != null && !disableReplyTo) {
exchange.setProperty("org.apache.camel.jms.replyDestination",
replyDestination);
if (!exchange.getPattern().isOutCapable())
exchange.setPattern(ExchangePattern.InOut);
}
{code}
This change will account for ExchangePattern.InOptionalOut. However, it will
also require the fix for bug CAMEL-1384 I submitted yesterday for everything to
work. In summary, a route could be defined as:
{code}
from("activemq:my_queue?exchangePattern=InOptionalOut").to("predict_weather://?reply_later=true");
{code}
Then if and only if the last processor does NOT set a out message, camel.jms
will not sent a reply. It is the downstream processors' responsibility to use
property "org.apache.camel.jms.replyDestination" to construct and sent the JMS
reply message.
The two changes in this bug and CAMEL-1384 are 100% backward compatible, since
InOptionalOut has not been considered for camel.jms before.
> EndpointMessageListener should respect ExchangePattern
> ------------------------------------------------------
>
> Key: CAMEL-1366
> URL: https://issues.apache.org/activemq/browse/CAMEL-1366
> Project: Apache Camel
> Issue Type: Bug
> Components: camel-jms
> Affects Versions: 1.6.0
> Environment: ActiveMQ/Camel
> Reporter: Michael Chen
>
> In all current releases,
> org.apache.camel.component.jms.EndpointMessageListener.onMessage() has the
> following logic (line 90 in 1.6.0 code):
> {code}
> // send the reply
> if (rce == null && body != null && !disableReplyTo) {
> sendReply(replyDestination, message, exchange, body);
> }
> {code}
> This logic should also respect ExchangePattern of the exchange, so I propose
> a change to:
> {code}
> // send the reply
> if (rce == null && body != null && exchange.isOutCapable()) {
> sendReply(replyDestination, message, exchange, body);
> }
> {code}
> This change allows a processing pattern where the route may change the
> ExchangePattern using methods like RouteBuilder.inOnly() to switch the MEP at
> will so that the reply is send at a later time (true asynchronous exchange).
> This processing pattern is particularly useful for integrating long running
> services. For example,
> {code}
> // Java DSL
> from("activemq:my_queue?exchangePattern=InOnly").to("predict_weather://?reply_later=true");
> // or
> from("activemq:my_queue2").inOnly().to("predict_weather://?reply_later=true");
> {code}
> The flaw of the current logic makes it impossible to do true asynchronous
> exchange, because 1) it does not respect the ExchangePattern; 2) if property
> "disableReplyTo" is used, the "org.apache.camel.jms.replyDestination"
> property will not be set (see method createExchange in the same file), thus
> downstream cannot find the reply destination.
> The proposed change can also deprecate the disableReplyTo property and put
> the MEP concept into good use.
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