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Sample 663: Using Multiple Sequences

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Last updated: Feb 11, 2020
3 min read

Note that WSO2 EI is shipped with the following changes to what is mentioned in this documentation:

  • <PRODUCT_HOME>/repository/samples/ directory that includes all Integration profile samples is changed to <EI_HOME>/samples/service-bus/.
  • <PRODUCT_HOME>/repository/samples/resources/ directory that includes all artifacts related to the Integration profile samples is changed to <EI_HOME>/samples/service-bus/resources/.

Introduction

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 (StockQuoteService microservice) and receive a response. If you look at the sample's XML configuration, you will see how this mediation is performed by two separate sequence definitions instead of one main sequence.

Prerequisites

For a list of prerequisites, see Prerequisites to Start the ESB Samples.

Building the sample

Expand the link given below to see the XML configuration of this sample. This configuration file (synapse_sample_663.xml) is available in the <EI_HOME>/samples/service-bus directory.

 synapse_sample_663.xml

<?xml version="1.0" encoding="UTF-8"?>
<definitions xmlns="http://ws.apache.org/ns/synapse">
<proxy name="SequenceBreakdownSampleProxy" startOnLoad="true" transports="http https">

      <description/>

      <target inSequence="StockQuoteSeq"/>

  </proxy>

  <sequence 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 name="StockQuoteErrorSeq">

      <log level="custom">

          <property name="Description" value="Error occurred in StockQuoteErrorSeq"/>

          <property name="Status" value="ERROR"/>

      </log>

  </sequence>

  <sequence 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="json" expression="$.name"/>

              <arg evaluator="json" expression="$.last"/>

              <arg evaluator="json" expression="$.low"/>

              <arg evaluator="json" expression="$.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 name="TransformAndRespondErrorSeq">

      <log level="custom">

          <property name="Description" value="Error occurred in TransformAndRespondSeq"/>

          <property name="Status" value="ERROR"/>

      </log>

  </sequence>

  <sequence name="CallStockQuoteErrorSeq">

      <log level="custom">

          <property name="Description" value="Error occurred in CallStockQuoteSeq"/>

          <property name="Status" value="ERROR"/>

      </log>

  </sequence>

  <sequence name="CallStockQuoteSeq" onError="CallStockQuoteErrorSeq">

      <switch source="//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:9090/stockquote/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:9090/stockquote/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:9090/stockquote/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>

</definitions>


Executing the sample

Send the following request to invoke the sample proxy service (named SequenceBreakdownSampleProxy) in the sample.

curl -v http://localhost:8280/services/SequenceBreakdownSampleProxy -H'Content-Type:application/xml' -d'<symbol>IBM</symbol>'

When this request is sent, SequenceBreakdownSampleProxy calls the StockQuoteSeq sequence. This sequence calls CallStockQuoteSeq and TransformAndRespondSeq respectively. In CallStockQuoteSeq, according to the symbol that is sent, the endpoint that is being called is switched using the /wiki/spaces/EI6xx/pages/49612596. Once the response is received from the endpoint, it is transformed with TransformAndRespondSeq , and sent back to the client. Also, note that an error sequence has been defined for each sequence, which will be executed in case of an error.

Analyzing the output

The output in the log for the above sample request would be as follows:

[2017-06-26 18:56:11,877] [EI-Core]  INFO - LogMediator SEQUENCE = StockQuoteSeq|DESCRIPTION = Request recieved
[2017-06-26 18:56:11,880] [EI-Core]  INFO - LogMediator SEQUENCE = CallStockQuoteSeq|DESCRIPTION = Calling IBM endpoint
[2017-06-26 18:56:11,941] [EI-Core]  INFO - LogMediator SEQUENCE = CallStockQuoteSeq|DESCRIPTION = Response received from IBM endpoint
[2017-06-26 18:56:11,942] [EI-Core]  INFO - LogMediator SEQUENCE = TransformAndRespondSeq|DESCRIPTION = Response is ready to be transformed
[2017-06-26 18:56:11,958] [EI-Core]  INFO - LogMediator SEQUENCE = TransformAndRespondSeq|DESCRIPTION = Responding back to the client with the transformed response

As shown in the above log, since the “symbol” that is sent in the request is “IBM”, the request is routed to the IBM endpoint. Once the response from the IBM endpoint is received, it is transformed according to the specified template and sent to the client. 

Shown below is the response that will be received by the client.


<Information>
   <Name>International Business Machines</Name>
   <Last>149.62</Last>
   <High>150.78</High>
   <Low>149.18</Low>
</Information>
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