Mule Dev Tricks: Using xpath3

Introduction

Even though today most web services using RESTful architecture, there are still a lot of legacy systems using SOAP. Handling xml file is challenging, if not difficult. Fortunately, Mule Application platform provide several utilities to alleviate the pain. The most powerful component is Dataweave, which is very handle to build SOAP request and handle responses. However, some cases, xpath3 is an easier solution. Sometimes it may be the best solution, for instance, if we want to split the xml payload based on certain node.

In this short article, I will introduce two use cases:

1. Extract values from xml payload
2. Split the payload

Use Case One: Extract Value Of An Element

Input Example

Here is the input:

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<!--xml version="1.0" encoding="UTF-8"?--> <wd:create_position_response xmlns:env="http://schemas.xmlsoap.org/soap/envelope/" xmlns:wd="urn:com.workday/bsvc" wd:version="v27.0">     <wd:event_reference wd:descriptor="Create Position: SOA Architect">         <wd:id wd:type="WID">31bf3ce3d6bb1025d71346c6ec276bd6</wd:id>     </wd:event_reference>     <wd:position_reference wd:descriptor="SOA Architect (Unfilled)">         <wd:id wd:type="WID">31bf3ce3d6bb1025d71348e2f1c26bdc</wd:id>         <wd:id wd:type="Position_ID">35119960</wd:id>     </wd:position_reference> </wd:create_position_response>

I want to extract the value of Position_ID in the line of:

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1	<wd:id wd:type="Position_ID">35119960</wd:id>

Solution

There are two solutions in this case. The first is:

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1	#[xpath3('/*:Create_Position_Response/*:Position_Reference/*:ID[2]')]

The above MEL will assign position_id to 35119960. Note: XML node count starting from 1 not from 0 as in Java array.

The other better solution is the following:

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1	#[xpath3('/*:Create_Position_Response/*:Position_Reference/*:ID[@*:type=\'Position_ID\']')]

Here is the trick is \/*:ID[@*:type=\'Position_ID\'].

1. Refer element attribute using [@*:type]
2. Escape the single quote with backslash \'

Use Case Two: Use xpath3 To Split Payload

Example Input

In this use case, I would like to extract the node of StockMovementData, so that I can process the data.

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<!--xml version="1.0"?--> <stockmovementdatarequest xmlns:p1="urn:ams.com.au:dynamo:3pl:am:SAP_AM_I_005:StockMovement" xmlns:a="http://www.edi.com.au/EnterpriseService">     <header>         <from>Warehouse</from>         <to>Location</to>         <unique_id>idm1468201212</unique_id>         <datetimestamp>2016-04-13T11:55:30.263+10:00</datetimestamp>     </header>     <stockmovementdata>         <serialised_material>YES</serialised_material>         <datetime>2016-04-13T11:55:30.263+10:00</datetime>         <from_location>30-80</from_location>         <to_location>client</to_location>         <material>7CAGL3G00</material>         <serial>700030011</serial>         <quantity>100</quantity>     </stockmovementdata>     <stockmovementdata>         <serialised_material>YES</serialised_material>         <datetime>2016-04-13T11:55:30.263+10:00</datetime>         <from_location>30-80</from_location>         <to_location>client</to_location>         <material>7CAGL3G00</material>         <serial>700029911</serial>         <quantity>100</quantity>     </stockmovementdata> </stockmovementdatarequest>

Here is the mule flow:

Solution

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<flow name="use_xpath3_splitter-Flow">         <http:listener config-ref="HTTP_Listener_Configuration" path="/advanced/splitter" doc:name="HTTP">         <splitter expression="#[xpath3('//StockMovementDataRequest/StockMovementData',payload,'NODESET')]" doc:name="Splitter">         <mulexml:dom-to-xml-transformer doc:name="DOM to XML">         <logger level="INFO" doc:name="Logger">         <collection-aggregator failontimeout="true" doc:name="Collection Aggregator">         <dw:transform-message doc:name="Transform Message">             <dw:set-payload><!--[CDATA[%dw 1.0 %output application/json --- payload]]--></dw:set-payload>         </dw:transform-message>         <logger message="#[payload]" level="INFO" doc:name="Logger">     </logger></collection-aggregator></logger></mulexml:dom-to-xml-transformer></splitter></http:listener></flow>

The above flow, split the xml payload using the following xpath3 expression:

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1 2	<splitter expression="#[xpath3('//StockMovementDataRequest/StockMovementData',payload,'NODESET')]" doc:name="Splitter"> </splitter>

Complete Mule Flow Configuration

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<!--xml version="1.0" encoding="UTF-8"?-->   <mule xmlns:dw="http://www.mulesoft.org/schema/mule/ee/dw" xmlns:tracking="http://www.mulesoft.org/schema/mule/ee/tracking" xmlns:mulexml="http://www.mulesoft.org/schema/mule/xml" xmlns:http="http://www.mulesoft.org/schema/mule/http" xmlns="http://www.mulesoft.org/schema/mule/core" xmlns:doc="http://www.mulesoft.org/schema/mule/documentation" xmlns:spring="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemalocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-current.xsd http://www.mulesoft.org/schema/mule/core http://www.mulesoft.org/schema/mule/core/current/mule.xsd http://www.mulesoft.org/schema/mule/http http://www.mulesoft.org/schema/mule/http/current/mule-http.xsd http://www.mulesoft.org/schema/mule/xml http://www.mulesoft.org/schema/mule/xml/current/mule-xml.xsd http://www.mulesoft.org/schema/mule/ee/tracking http://www.mulesoft.org/schema/mule/ee/tracking/current/mule-tracking-ee.xsd http://www.mulesoft.org/schema/mule/ee/dw http://www.mulesoft.org/schema/mule/ee/dw/current/dw.xsd">     <flow name="use_xpath3_extract_value-Flow">         <http:listener config-ref="HTTP_Listener_Configuration" path="/advanced/xpath3" doc:name="HTTP">         <mulexml:dom-to-xml-transformer doc:name="DOM to XML">         <set-variable variablename="position_id" value="#[xpath3('/*:Create_Position_Response/*:Position_Reference/*:ID[2]')]" doc:name="Variable">         <set-variable variablename="position_id2" value="#[xpath3('/*:Create_Position_Response/*:Position_Reference/*:ID[@*:type=\'Position_ID\']')]" doc:name="Variable">         <logger message="#[payload]" level="INFO" doc:name="Logger">     </logger></set-variable></set-variable></mulexml:dom-to-xml-transformer></http:listener></flow>     <flow name="use_xpath3_splitter-Flow">         <http:listener config-ref="HTTP_Listener_Configuration" path="/advanced/splitter" doc:name="HTTP">         <splitter expression="#[xpath3('//StockMovementDataRequest/StockMovementData',payload,'NODESET')]" doc:name="Splitter">         <mulexml:dom-to-xml-transformer doc:name="DOM to XML">         <logger level="INFO" doc:name="Logger">         <collection-aggregator failontimeout="true" doc:name="Collection Aggregator">         <dw:transform-message doc:name="Transform Message">             <dw:set-payload><!--[CDATA[%dw 1.0 %output application/json --- payload]]--></dw:set-payload>         </dw:transform-message>         <logger message="#[payload]" level="INFO" doc:name="Logger">     </logger></collection-aggregator></logger></mulexml:dom-to-xml-transformer></splitter></http:listener></flow> </mule>