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The Envelope Wrapper EIP allows existing systems to participate in a messaging exchange that places specific requirements on the message format, such as message header fields or encryption. It wraps application data inside an envelope that is compliant with the messaging infrastructure. The message is unwrapped when it arrives at the destination. For more information, refer to http://www.eaipatterns.com/EnvelopeWrapper.html.

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Figure 1: Envelope Wrapper EIP

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This example scenario receives a message with application data wrapped inside an envelope, unwraps the message, and sends it to a specific endpoint. The sender sends the request inside a SOAP envelopenvelope. Once the ESB receives the envelopenvelope, it unwraps the envelop it and sends it as a Plain Old XML (POX) request to the sample back-end Axis2 server.

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Before digging into implementation details, let's take a look at the relationship between the example scenario and the Envelope Wrapper EIP by comparing their core components.

Envelope Wrapper EIP (Figure 1: Enveloper Wrapper EIPFigure 2: )	Envelope Wrapper Example Scenario (Figure 2)
Wrapper	Stock Quote Request wrapped in SOAP
Messaging System	WSO2 ESB
Unwrapper	Address Endpoint format
Recipient	Stock Quote Service Instance

Info
An alternative implementation of this EIP is to have the wrapping be done by the Address Endpoint wrap from one envelope format to another (for example, wrapping a SOAP 1.1 envelope in a SOAP 1.2 envelope).

Environment setup

Download an and install the WSO2 ESB from http://wso2.com/products/enterprise-service-bus. For a list of prerequisites and step-by-step installation instructions, refer to Getting Started Installation Guide in the WSO2 ESB documentation.
Start the sample Axis2 server. For instructions, refer to the section Setting Up the ESB Samples Setup - Starting Sample Back-End Servicesthe Axis2 server in the WSO2 ESB documentation.

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Start the ESB server and log into its management console UI (https://localhost:9443/carbon). In the management console, navigate to the Main Menu, click Service Bus and then Source View menu and click Source View in the Service Bus section. Next, copy and paste the following configuration, which helps you explore the example scenario, to the source view.

Anchor

	step3
	step3

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Send the following request using a SOAP client like SOAP UI SoapUI, and monitor the message using TCPMon.

Code Block

language	html/xml

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ser="http://services.samples" xmlns:xsd="http://services.samples/xsd">
   <soapenv:Header/>
   <soapenv:Body>
      <ser:getQuote>     
         <ser:request>           
            <xsd:symbol>Foo<symbol>foo</xsd:symbol>
         </ser:request>        
      </ser:getQuote>
   </soapenv:Body>
</soapenv:Envelope>

Notice that the request data is inside a SOAP envelope. When the request was monitored through TCPMon before it was sent to the ESB, it was structures structured as follows.:

Code Block

POST /services/EnvelopeUnwrapProxy HTTP/1.1 
Accept-Encoding: gzip,deflate 
Content-Type: text/xml;charset=UTF-8 
SOAPAction: "urn:getQuote" 
Content-Length: 385 
Host: 127.0.0.1:8281 
Connection: Keep-Alive 
User-Agent: Apache-HttpClient/4.1.1 (java 1.5) 
 
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ser="http://services.samples" xmlns:xsd="http://services.samples/xsd">
   <soapenv:Header/>
   <soapenv:Body>
      <ser:getQuote>     
         <ser:request>           
            <xsd:symbol>Foo<symbol>foo</xsd:symbol>
         </ser:request>        
      </ser:getQuote>
   </soapenv:Body>
</soapenv:Envelope>

The request sent to the back-end Axis2 server has the following structure.:

Code Block

POST /services/SimpleStockQuoteService HTTP/1.1 
Content-Type: application/xml; charset=UTF-8 
Accept-Encoding: gzip,deflate 
SOAPAction: urn:getQuote 
Transfer-Encoding: chunked 
Host: localhost:9000 
Connection: Keep-Alive 
User-Agent: Synapse-HttpComponents-NIO 
 
e0 
<ser:getQuote xmlns:ser="http://services.samples">     
         <ser:request>           
            <xsd:symbol xmlns:xsd="http://services.samples/xsd">Foo<>foo</xsd:symbol>
         </ser:request>        
      </ser:getQuote> 
0

This means that the SOAP envelope was removed by the ESB.

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Let's investigate the elements of the ESB configuration in detail. The line numbers below are mapped with the ESB configuration illustrated in step 3 shown above.

address [line 8 in ESB config] - The endpoint address contains the attribute format='pox', which makes the ESB convert incoming requests to Plain Old XML. Other supported formats for wrapping include soap11, soap12 and get. For more information, refer to the Address Endpoint mediator.

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Environment setup