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XML Gateway

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XML Gateway Authors: Mamoon Yunus, Dirk Zwart, Rizwan Mallal, Mark O'Neill, Ron Schmelzer

Related Topics: Cloud Computing, SOA & WOA Magazine, XML Gateway

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How to Use XML Gateway with Asynchronous Web Service Using WS-Addressing

One of the main uses of an XML gateway is to encapsulate the end-point of the actual service from the caller

I wanted to spend some time here to review in a little more detail the gateway and what it does when it processes the request, and handles the callback. When the request arrives, the original message looks something like this:


<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing">
<soap:Header>
<wsa:MessageID>uuid:6B29FC40-CA47-1067-B31D-00DD010662DA</wsa:MessageID>
<wsa:ReplyTo>
<wsa:Address>http://localhost:11000/callback</wsa:Address>
</wsa:ReplyTo>
<wsa:To>http://localhost:12000/SoapContext/SoapGreeterPort</wsa:To>
<wsa:Action>Greet</wsa:Action>
</soap:Header>
<soap:Body>
<x1:greetMeOneWay xmlns:x1="http://apache.org/hello_world_soap_http/types">
<!-- Element must appear exactly once -->
<x1:requestType>Asynch Client using WS-Addressing</x1:requestType>
</x1:greetMeOneWay>
</soap:Body>
</soap:Envelope>


The message gets picked up and processed by the following policy:



I'm using policy shortcuts to encapsulate all of the details, but you get the basic idea. The message leaving the gateway has been transformed to have the gateway address in the wsa:ReplyTo and the server's address in the wsa:To. This is the resulting message sent to the server.


<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing">
<soap:Header>
<wsa:MessageID>uuid:6B29FC40-CA47-1067-B31D-00DD010662DA</wsa:MessageID>


<wsa:Action>Greet</wsa:Action>
<wsa:ReplyTo>
<wsa:Address>http://localhost:12000/SoapContext/GreetCallbackSoapPort</wsa:Address>
</wsa:ReplyTo><wsa:To>http://localhost:13000/SoapContext/SoapGreeterPort</wsa:To></soap:Header>
<soap:Body>
<x1:greetMeOneWay xmlns:x1="http://apache.org/hello_world_soap_http/types">
<!-- Element must appear exactly once -->
<x1:requestType>Asynch Client using WS-Addressing</x1:requestType>
</x1:greetMeOneWay>
</soap:Body>
</soap:Envelope>


So when the reply comes back from the server, and arrives back at the gateway, it has a new wsa:messageId, but the original messageId is available in the wsa:RelatesTo header.


<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Header>
<wsa:Action
xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing" />
<wsa:MessageID
xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing">
uuid:Id-0000012e5303f409-0000000000a96fd2-2
</wsa:MessageID>
<wsa:RelatesTo
xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing">
uuid:6B29FC40-CA47-1067-B31D-00DD010662DA
</wsa:RelatesTo>
<wsa:To xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing">
http://localhost:12000/SoapContext/GreetCallbackSoapPort
</wsa:To>
</soap:Header>
<soap:Body>
<x1:greetMeResponse
xmlns:x1="http://apache.org/hello_world_soap_http/types">
<!-- Element must appear exactly once -->
<x1:responseType>
Hello Asynch Client using WS-Addressing
</x1:responseType>
</x1:greetMeResponse>
</soap:Body>
</soap:Envelope>


The callback policy then picks this message up and applies the following filters:




This is the basic caching pattern used by the gateway. The cache's key is the wsa:messageId set by the incoming request. This can then be retrieved from the cache by pulling the wsa:RealtesTo messageId. The resulting URL is then set as the destination (wsa:To) of the response, and the reply is sent. The final message looks like this:


<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Header>
<wsa:Action
xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing" />
<wsa:MessageID
xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing">
uuid:Id-0000012e53675a57-0000000001f76db2-18
</wsa:MessageID>
<wsa:RelatesTo
xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing">
uuid:6B29FC40-CA47-1067-B31D-00DD010662DA
</wsa:RelatesTo>
<wsa:To xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing">
http://localhost:11000/callback
</wsa:To>
</soap:Header>
<soap:Body>
<x1:greetMeResponse
xmlns:x1="http://apache.org/hello_world_soap_http/types">
<!-- Element must appear exactly once -->
<x1:responseType>
Hello Asynch Client using WS-Addressing
</x1:responseType>
</x1:greetMeResponse>
</soap:Body>
</soap:Envelope>

I've exported this project and added it to the Vordel Incubator. You can download the config here. Let me know what you think.















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