Sample 353: Using Ruby Scripts for Mediation

Introduction

The ESB Script mediator can be programmed using any BSF compatible programming language. This Sample demonstrates how to use Ruby Scripts for mediation using the Script mediator.

Prerequisites

Support for Ruby scripting. To enable Ruby support, see Setting up Ruby Support.

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

Building the sample

The XML configuration for this sample is as follows: 

<definitions xmlns="http://ws.apache.org/ns/synapse">

    <localEntry key="stockquoteScript" src="file:repository/samples/resources/script/stockquoteTransform.rb"/>
    <in>
        <!-- transform the custom quote request into a standard quote request expected by the service -->
        <script language="rb" key="stockquoteScript" function="transformRequest"/>

        <!-- send message to real endpoint referenced by name "stockquote" and stop -->
        <send>
            <endpoint name="stockquote">
                <address uri="http://localhost:9000/services/SimpleStockQuoteService"/>
            </endpoint>
        </send>
    </in>
    <out>
        <!-- transform the standard response back into the custom format the client expects -->
        <script language="rb" key="stockquoteScript" function="transformResponse"/>
        <send/>
    </out>
</definitions> 

This configuration file  synapse_sample_353.xml is available in the <ESB_HOME>/repository/samples directory.

To build the sample

1. Start the ESB with the sample 353 configuration. For instructions on starting a sample ESB configuration, see Starting the ESB with a sample configuration.
   The operation log keeps running until the server starts, which usually takes several seconds. Wait until the server has fully booted up and displays a message similar to "WSO2 Carbon started in n seconds."

2. Start the Axis2 server. For instructions on starting the Axis2 server, see Starting the Axis2 server.

3. Deploy the back-end service SimpleStockQuoteService. For instructions on deploying sample back-end services, see Deploying sample back-end services.

The script used in this sample  stockquoteTransform.rb is as follows:

<x><![CDATA[
require 'rexml/document'
include REXML
def transformRequest(mc)
  newRequest= Document.new '<m:getQuote xmlns:m="http://services.samples">'<<
            '<m:request><m:symbol></m:symbol></m:request></m:getQuote>'
  newRequest.root.elements[1].elements[1].text = mc.getPayloadXML().root.elements[1].get_text
  mc.setPayloadXML(newRequest)
end
def transformResponse(mc)
  newResponse = Document.new '<m:CheckPriceResponse xmlns:m="http://services.samples/xsd"><m:Code>' <<
    '</m:Code><m:Price></m:Price></m:CheckPriceResponse>'
  lastPrice=mc.getPayloadXML().root.elements[1].get_elements('*:last')
  code=mc.getPayloadXML().root.elements[1].get_elements('*:symbol') 
  newResponse.root.elements[1].text =code[0].get_text
  newResponse.root.elements[2].text =lastPrice[0].get_text 
  mc.setPayloadXML(newResponse)
end
]]></x>

The script has two functions, transformRequest and transformResponse, and the ESB configuration uses the function attribute to specify which function should be invoked. 

Executing the sample

The sample client used here is the Stock Quote Client, which can operate in several modes. For further details on this sample client and its operation modes, see Stock Quote Client.

To execute the sample client

Run the following command from the <ESB_HOME>/samples/axis2Client directory.

ant stockquote -Daddurl=http://localhost:9000/services/SimpleStockQuoteService -Dtrpurl=http://localhost:8280/ -Dmode=customquote

Analyzing the output

You will see that the ESB uses the Script mediator and the function specified in the configuration to convert the custom request to a standard quote request.  You will also see that the response received is subsequently transformed and sent back to the client.

For additional examples that use the Script Mediator, see Using Scripts in Mediation (Script Mediator).