Need help with polling to a json based HTTP service

[biju.kunjummen]

Hi, I need a little help with the right way to poll to an external json based HTTP service using http gateway. I have requirement where I have to poll an external http json based service every minute and get the data into the messaging system. I would have assumed that an http inbound adapter/gateway would have been the right fit, but it behaves differently, it essentially exposes an http endpoint and expect the calls to come in.

So it sounds like a http outbound gateway is what I have to use. However, since it is a outbound gateway which gets triggered based on the availability of a message in a channel, I have to artificially put a dummy message in a channel to trigger the outbound http gateway to get a message in, this way:

	<int:channel id="quakeinfotrigger.channel"></int:channel>	
	<int:inbound-channel-adapter channel="quakeinfotrigger.channel" expression="@triggerChannelAdapter.trigger()">
		<int:poller fixed-delay="60000"></int:poller>
	</int:inbound-channel-adapter>

	<int:channel id="quakeinfo.channel">
		<int:queue capacity="10"/>
	</int:channel>
	<int-http:outbound-gateway id="quakerHttpGateway"
	    request-channel="quakeinfotrigger.channel"
	    url="http://earthquake.usgs.gov/earthquakes/feed/geojson/all/hour"
	    http-method="GET"
	    expected-response-type="java.lang.String"
	    charset="UTF-8"
	    reply-timeout="5000"
	    reply-channel="quakeinfo.channel">	    
	</int-http:outbound-gateway>

So my question is - Is there a better way to do this?

[Cleric]

Hi!

You really go right way!
However your 'dummy' payload can be like this:

<int:inbound-channel-adapter channel="quakeinfotrigger.channel" expression="''">

Take care,
Artem

[biju.kunjummen]

Nice, thanks Artem, that works and avoids needing to create a dummy adapter also.