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Breaking Complex Flows into Multiple Sequences

This sample demonstrates how a complex sequence can be separated into a set of simpler sequences. In this sample, you will send a simple request to a back-end service (Stock Quote service) and receive a response. If you look at the sample's XML configuration, you will see how this mediation is performed by several sequence definitions instead of one main sequence.

Synapse configuration

Following are the integration artifacts that we can used to implement this scenario. See the instructions on how to build and run this example.

  • Proxy service:

    <proxy xmlns="http://ws.apache.org/ns/synapse" name="SequenceBreakdownSampleProxy" startOnLoad="true" transports="http https">
          <description/>
          <target inSequence="StockQuoteSeq"/>
    </proxy>

  • Mediation sequences:

    <sequence xmlns="http://ws.apache.org/ns/synapse" name="StockQuoteSeq" onError="StockQuoteErrorSeq">
        <log level="custom">
            <property name="Sequence" value="StockQuoteSeq"/>
            <property name="Description" value="Request recieved"/>
        </log>
        <sequence key="CallStockQuoteSeq"/>
        <sequence key="TransformAndRespondSeq"/>
    </sequence>
    <sequence xmlns="http://ws.apache.org/ns/synapse" name="StockQuoteErrorSeq">
        <log level="custom">
            <property name="Description" value="Error occurred in StockQuoteErrorSeq"/>
            <property name="Status" value="ERROR"/>
        </log>
    </sequence>
    <sequence xmlns="http://ws.apache.org/ns/synapse" name="TransformAndRespondSeq" onError="TransformAndRespondErrorSeq">
        <log level="custom">
            <property name="Sequence" value="TransformAndRespondSeq"/>
            <property name="Description" value="Response is ready to be transformed"/>
        </log>
        <payloadFactory media-type="xml">
            <format>
                <Information xmlns="">
                    <Name>$1</Name>
                    <Last>$2</Last>
                    <High>$3</High>
                    <Low>$4</Low>
                </Information>
            </format>
            <args>
                <arg evaluator="xml" xmlns:m0="http://services.samples/xsd" expression="//m0:name"/>
                <arg evaluator="xml" xmlns:m0="http://services.samples/xsd" expression="//m0:last"/>
                <arg evaluator="xml" xmlns:m0="http://services.samples/xsd" expression="//m0:low"/>
                <arg evaluator="xml" xmlns:m0="http://services.samples/xsd" expression="//m0:high"/>
            </args>
        </payloadFactory>
        <log level="custom">
            <property name="Sequence" value="TransformAndRespondSeq"/>
            <property name="Description" value="Responding back to the client with the transformed response"/>
        </log>
        <respond/>
    </sequence>
    <sequence xmlns="http://ws.apache.org/ns/synapse" name="TransformAndRespondErrorSeq">
        <log level="custom">
            <property name="Description" value="Error occurred in TransformAndRespondSeq"/>
            <property name="Status" value="ERROR"/>
        </log>
    </sequence>
    <sequence xmlns="http://ws.apache.org/ns/synapse" name="CallStockQuoteErrorSeq">
          <log level="custom">
              <property name="Description" value="Error occurred in CallStockQuoteSeq"/>
              <property name="Status" value="ERROR"/>
          </log>
    </sequence>
    <sequence xmlns="http://ws.apache.org/ns/synapse" name="CallStockQuoteSeq" onError="CallStockQuoteErrorSeq">
        <switch source="//ns:symbol" xmlns:ns="http://org.apache.synapse/xsd">
            <case regex="IBM">
                <log level="custom">
                    <property name="Sequence" value="CallStockQuoteSeq"/>
                    <property name="Description" value="Calling IBM endpoint"/>
                </log>
                <call blocking="true">
                    <endpoint>
                        <http method="GET" uri-template="http://localhost:8290/stockquote/view/IBM"/>
                    </endpoint>
                </call>
                <log level="custom">
                    <property name="Sequence" value="CallStockQuoteSeq"/>
                    <property name="Description" value="Response received from IBM endpoint"/>
                </log>
            </case>
            <case regex="GOOG">
                <log level="custom">
                    <property name="Sequence" value="CallStockQuoteSeq"/>
                    <property name="Description" value="Calling GOOG endpoint"/>
                </log>
                <call blocking="true">
                    <endpoint>
                        <http method="GET" uri-template="http://localhost:8290/stockquote/view/GOOG"/>
                    </endpoint>
                </call>
                <log level="custom">
                    <property name="Sequence" value="CallStockQuoteSeq"/>
                    <property name="Description" value="Response received from GOOG endpoint"/>
                </log>
            </case>
            <case regex="AMZN">
                <log level="custom">
                    <property name="Sequence" value="CallStockQuoteSeq"/>
                    <property name="Description" value="Calling AMZN endpoint"/>
                </log>
                <call blocking="true">
                    <endpoint>
                        <http method="GET" uri-template="http://localhost:8290/stockquote/view/AMZN"/>
                    </endpoint>
                </call>
                <log level="custom">
                    <property name="Sequence" value="CallStockQuoteSeq"/>
                    <property name="Description" value="Response received from AMZN endpoint"/>
                </log>
            </case>
            <default>
                <log level="custom">
                    <property name="Sequence" value="CallStockQuoteSeq"/>
                    <property name="Description" value="Invalid Symbol"/>
                    <property name="Status" value="ERROR"/>
                </log>
                <drop/>
            </default>
        </switch>
    </sequence>
  • REST API, which calls the back-end service.

    <api xmlns="http://ws.apache.org/ns/synapse" name="StockQuoteAPI" context="/stockquote">
           <resource methods="GET" uri-template="/view/{symbol}">
              <inSequence>
                 <payloadFactory media-type="xml">
                    <format>
                       <m0:getQuote xmlns:m0="http://services.samples">
                          <m0:request>
                             <m0:symbol>$1</m0:symbol>
                          </m0:request>
                       </m0:getQuote>
                    </format>
                    <args>
                       <arg evaluator="xml" expression="get-property('uri.var.symbol')"/>
                    </args>
                 </payloadFactory>
                 <header name="Action" scope="default" value="urn:getQuote"/>
                 <send>
                    <endpoint>
                       <address uri="http://localhost:9000/services/SimpleStockQuoteService" format="soap11"/>
                    </endpoint>
                 </send>
              </inSequence>
              <outSequence>
                 <send/>
              </outSequence>
              <faultSequence/>
           </resource>
    </api>

Build and run

Create the artifacts:

  1. Set up WSO2 Integration Studio.
  2. Create an ESB Solution project.
  3. Create the proxy service, the mediation sequences, and the REST API with the configurations given above.
  4. Deploy the artifacts in your Micro Integrator.

Set up the back-end service:

  1. Download the stockquote_service.jar.
  2. Open a terminal, navigate to the location of the downloaded service, and run it using the following command:

    java -jar stockquote_service.jar

Send a request to invoke the service:

POST http://localhost:8290/services/SequenceBreakdownSampleProxy.SequenceBreakdownSampleProxyHttpSoap11Endpoint HTTP/1.1
Accept-Encoding: gzip,deflate
Content-Type: text/xml;charset=UTF-8
SOAPAction: "urn:mediate"
Content-Length: 321
Host: Chanikas-MacBook-Pro.local:8290
Connection: Keep-Alive
User-Agent: Apache-HttpClient/4.1.1 (java 1.5)


<?xml version="1.0" encoding="UTF-8"?>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
   <soapenv:Header />
   <soapenv:Body>
      <placeOrder xmlns="http://org.apache.synapse/xsd">
         <order>
            <price>50</price>
            <quantity>10</quantity>
            <symbol>IBM</symbol>
         </order>
      </placeOrder>
   </soapenv:Body>
</soapenv:Envelope>

You will receive the following response:

HTTP/1.1 200 OK
SOAPAction: "urn:mediate"
Host: Chanikas-MacBook-Pro.local:8290
Accept-Encoding: gzip,deflate
Content-Type: text/xml;charset=UTF-8
Date: Wed, 02 Oct 2019 10:01:25 GMT
Transfer-Encoding: chunked
Connection: Keep-Alive

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
   <soapenv:Body>
      <Information>
         <Name>IBM Company</Name>
         <Last>69.75734480144942</Last>
         <High>-69.47003220786323</High>
         <Low>72.09188473048964</Low>
      </Information>
   </soapenv:Body>
</soapenv:Envelope>
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