dismiss message in Apache Camel - apache-camel

Question

Hope this doesn't sound ridiculous, but how can I discard a message in Camel on purpose?
Until now, I sent them to the Log-Component, but meanwhile I don't even want to log the withdrawal.
Is there a /dev/null Endpoint in Camel?

Answer 1

You can use the message filter eip to filter out unwanted messages.
http://camel.apache.org/message-filter
There is no dev/null, component.
Also there is a < stop /> you can use in the route, and when a message hit that, it will stop continue routing.
And the closest we got on a dev/null, is to route to a log, where you set logLeve=OFF as option.

Answer 2

With credit to my colleague (code name: cayha)...
You can use the Stub Component as a camel endpoint that is equivalent to /dev/null.
e.g.
activemq:route?abc=xyz
becomes
stub:activemq:route?abc=xyz
Although I am not aware of the inner workings of this component (and if there are dangers for memory leaks, etc), it works for me and I can see no drawbacks in doing it this way.

Answer 3

one can put uri/mock-uri to the config using property component
<camelContext ...>
<propertyPlaceholder id="properties" location="ref:myProperties"/>
</camelContext>
// properties
cool.end=mock:result
# cool.end=result
// route
from("direct:start").to("properties:{{cool.end}}");

Answer 4

I'm a little late to the party but you can set a flag on the exchange and use that flag to skip only that message (by calling stop) if it doesn't meet your conditions.
#Override
public void configure() throws Exception {
from()
.process(new Processor() {
#SuppressWarnings("unchecked")
#Override
public void process(Exchange exchange) throws Exception {
exchange.setProperty("skip", false);
byte[] messageBytes = exchange.getIn().getBody(byte[].class);
if (<shouldNotSkip>) {
} else { //skip
exchange.setProperty("skip", true);
}
}
}).choice()
.when(exchangeProperty("skip").isEqualTo(true))
.stop()
.otherwise()
.to();
}

Answer 5

I am using activemq route and needs to send reply in normal cases, so exchange pattern is InOut. When I configure a filter in the route I find that even it does not pass message to next step, the callback is executed(sending reply), just same as the behavior when calling stop(). And it will send the same message back to reply queue, which is not desirable.
What I do is to change the exchange pattern to InOnly conditionally and stop if I want to filter out the message, so reply is not sent. MAIN_ENDPOINT is a direct:main endpoint I defined to include normal business logic.
from("activemq:queue:myqueue" + "?replyToSameDestinationAllowed=true")
.log(LoggingLevel.INFO, "Correlation id is: ${header.JMSCorrelationID}; will ignore if not null")
.choice()
.when(simple("${header.JMSCorrelationID} == null"))
.to(MAIN_ENDPOINT)
.endChoice()
.otherwise()
.setExchangePattern(ExchangePattern.InOnly)
.stop()
.endChoice()
.end();
Note that this message is also consumed and not in the queue anymore. If you want to preserve the message in the queue(not consuming it), you may just stop() or just filter() so the callback(sending reply which is the original message) works, putting the message back to the queue.
Using only filter() would be much simpler:
from("activemq:queue:myqueue" + "?replyToSameDestinationAllowed=true")
.log(LoggingLevel.INFO, "Correlation id is: ${header.JMSCorrelationID}; will ignore if not null")
.filter(simple("${header.JMSCorrelationID} == null"))
.to(MAIN_ENDPOINT);