XML to XML transformation via Smooks Mediator in WSO2 ESB

Smooks is an extensible framework for building applications for processing XML and non XML data (CSV, EDI, Java etc). This example demonstrates how xml to xml transformation can be done using the smooks mediator in WSO2 ESB. WSO2 ESB provides XSLT, FastXSLT, Enrich, PayloadFactory, Smooks and XQuery mediators to transform messages from XML to XML. Choice of a particular mediator out of these, depends on the complexity of the use case. For a simple transformation  enrich or PayloadFactory would be the best choice. For a complex transformation XSLT, FastXSLT, XQuery or Smooks can be used. In this article I will use smooks mediator for xml to xml transformation.

Having said that let’s get some hands on smooks using WSO2 ESB. For this sample I am using WSO2ESB 4.8.1 version. First locate the axis2.xml file under the $ESB_HOME/repository/conf/axis2 directory and enable vfs transport. For this uncomment the vfs transport sender and receiver elements.  Then move on to $ESB_HOME/bin directory and execute ./wso2server.sh startup script to start the ESB.

Smooks consists of a configuration file where all the transformation specific stuffs are stated. A sample smooks configuration [1] used for this article is given below. Also all the configurations used in this article can be found here [2].

	<?xml version="1.0"?>
	<smooks-resource-list xmlns="http://www.milyn.org/xsd/smooks-1.1.xsd" xmlns:core="http://www.milyn.org/xsd/smooks/smooks-core-1.3.xsd" xmlns:ftl="http://www.milyn.org/xsd/smooks/freemarker-1.1.xsd">
	<!--
	Filter the message using the SAX Filter (i.e. not DOM, so no
	intermediate DOM for the "complete" message - there are "mini" DOMs
	for the NodeModels below)....
	-->
	<core:filterSettings defaultSerialization="false" type="SAX"/>
	<!--
	Create 2 NodeModels. One high level model for the "order"
	(header etc) and then one per "order-item".
	These models are used in the FreeMarker templating resources
	defined below. You need to make sure you set the selector such
	that the total memory footprint is as low as possible. In this
	example, the "order" model will contain everything accept the
	<order-item>data (the main bulk of data in the message). The
	"order-item" model only contains the current <order-item>data
	(i.e. there's max 1 order-item in memory at any one time).
	-->
	<resource-config selector="order,order-item">
	<resource>org.milyn.delivery.DomModelCreator</resource>
	</resource-config>
	<!--
	Apply the first part of the template when we reach the start
	of the <order-items>element. Apply the second part when we
	reach the end.
	Note the <?TEMPLATE-SPLIT-PI?>Processing Instruction in the
	template. This tells Smooks where to split the template,
	resulting in the order-items being inserted at this point.
	-->
	<ftl:freemarker applyOnElement="order-items">
	<ftl:template>
	<!--<salesorder><details><orderid>${order.@id}</orderid><customer><id>${order.header.customer.@number}</id><name>${order.header.customer}</name></customer></details><itemList><?TEMPLATE-SPLIT-PI?></itemList></salesorder>-->
	</ftl:template>
	</ftl:freemarker>
	<!--
	Output the <order-items>elements. This will appear in the
	output message where the <?TEMPLATE-SPLIT-PI?>token appears in the
	order-items template.
	-->
	<ftl:freemarker applyOnElement="order-item">
	<ftl:template>
	<!-- <item><id>${.vars["order-item"].@id}</id><productId>${.vars["order-item"].product}</productId><quantity>${.vars["order-item"].quantity}</quantity><price>${.vars["order-item"].price}</price></item>-->
	</ftl:template>
	</ftl:freemarker>
	</smooks-resource-list>

view raw smooks_config.xml hosted with ❤ by GitHub

Let’s place this smooks configuration file inside the registry. For this in the web interface under the main menu, click on browse, and create a collection named smooks under the _system/config. Then save the above configuration in your file system and name it as ‘smooks_config.xml’. Move on to the created collection named ‘smooks’ and add this configuration file as a resource to that.

Then go to the source view under the main menu and add the following proxy configuration.

	<?xml version="1.0" encoding="UTF-8"?>
	<proxy xmlns="http://ws.apache.org/ns/synapse" name="smook_proxy" startOnLoad="true" statistics="disable" trace="disable" transports="https,http,vfs">
	<target>
	<inSequence>
	<property name="FORCE_SC_ACCEPTED" value="true" scope="axis2" type="STRING" />
	<property name="OUT_ONLY" value="true" scope="default" type="STRING" />
	<log level="full" />
	<smooks config-key="conf:/smooks/smooks_config.xml">
	<input type="xml" />
	<output type="xml" />
	</smooks>
	<log level="full" />
	</inSequence>
	</target>
	<parameter name="transport.PollInterval">5</parameter>
	<parameter name="transport.vfs.ActionAfterProcess">MOVE</parameter>
	<parameter name="transport.vfs.FileURI">file:///home/ravindra/ESB-Team/smooks-article/in</parameter>
	<parameter name="transport.vfs.MoveAfterProcess">file:///home/ravindra/ESB-Team/smooks-article/result</parameter>
	<parameter name="transport.vfs.MoveAfterFailure">file:///home/ravindra/ESB-Team/smooks-article/result</parameter>
	<parameter name="transport.vfs.FileNamePattern">.*.xml</parameter>
	<parameter name="transport.vfs.ContentType">application/xml</parameter>
	<parameter name="transport.vfs.ActionAfterFailure">MOVE</parameter>
	<description />
	</proxy>

view raw smook_proxy.xml hosted with ❤ by GitHub

The input that we need to transform is given below. Take that and save into a file named input.xml under the file system location specified for the transport.vfs.FileURI parameter.

	<?xml version="1.0" encoding="UTF-8"?>
	<order id="332">
	<header>
	<customer number="123">Joe</customer>
	</header>
	<order-items>
	<order-item id="1">
	<product>1</product>
	<quantity>2</quantity>
	<price>8.80</price>
	</order-item>
	<!-- etc etc -->
	</order-items>
	</order>

view raw input.xml hosted with ❤ by GitHub

The proxy will pick that up from the specified file system location via the vfs transport and transform it as specified in the smooks_config.xml file. Then the output will be logged in the ESB console. A sample output is given below.

	<?xml version="1.0" encoding="UTF-8"?>
	<salesorder>
	<details>
	<orderid>332</orderid>
	<customer>
	<id>123</id>
	<name>Joe</name>
	</customer>
	</details>
	<itemList>
	<item>
	<id>1</id>
	<productId>1</productId>
	<quantity>2</quantity>
	<price>8.80</price>
	</item>
	</itemList>
	</salesorder>

view raw output.xml hosted with ❤ by GitHub

Here I have covered only xml to xml transformation scenario via the smooks mediator. You may refer to our documentation sample [3] for text to xml transformation. There are lot more combinations remaining. I hope that you would try them out.

References

[1] http://www.smooks.org/mediawiki/index.php?title=V1.4:xml-to-xml

[2] https://www.dropbox.com/s/953a7gt8xk600ye/smooks-mediator-synapse-config.zip?dl=0

[3] https://docs.wso2.com/display/ESB481/Sample+654%3A+Smooks+Mediator