how to reuse the xpr file in Mule 4 - mule

Question

In my case, I'm doing a migration from Mule 3 to Mule 4.
This flow, which includes transformers like DOM to XML, XML to DOM, and an expression component, needs to be migrated.
In Mule 4, I want to reuse the xrp file.
My flow for XML payload transform uses an XPR file by the expression component in Mule 3.
<flow name="rate-dtostepFlow">
<http:listener config-ref="HTTP_Listener_Configuration" path="/dtostep" allowedMethods="POST" doc:name="HTTP"/>
<mulexml:xml-to-dom-transformer returnClass="org.dom4j.Document" doc:name="XML to DOM"/>
<set-variable variableName="domPayload" value="#[payload]" doc:name="set domPayload "/>
<expression-component file="xpr/responseStubCannasure.xpr" doc:name="Expression"/>
<mulexml:dom-to-xml-transformer doc:name="DOM to XML"/>
</flow>
Input XML: https://github.com/Manikandan99/rate-dtostep/blob/master/request.xml
Output XML: https://github.com/Manikandan99/rate-dtostep/blob/master/response.xml
my MULE 3 application : https://github.com/Manikandan99/rate-dtostep/tree/master/rate-dtostep
ResponseStubcannsure xpr file:
import org.dom4j.*;
import java.util.*;
import java.util.logging.Logger;
Logger logger = Logger.getLogger("");
dtoCoverageStepsNodes = flowVars.domPayload.selectNodes("//DTOCoverage[#Status=\'Active\']/DTOSteps");
for (Node node : dtoCoverageStepsNodes){
//logger.info("inside: detach");
node.detach();
}
dtoCoverageNodes = flowVars.domPayload.selectNodes("//DTOCoverage[#Status=\'Active\']");
int i = 500;
for (Node node : dtoCoverageNodes){
//node.detach();
//logger.info("inside: assign prem");
node.addAttribute("FullTermAmt", Integer.toString(i));
node.addElement("DTOSteps");
stepNode = node.selectSingleNode("DTOSteps");
stepNode.addElement("DTOStep")
.addAttribute("Order","1")
.addAttribute("Name","Final Premium")
.addAttribute("Desc","Final Premium Desc")
.addAttribute("Operation","=")
.addAttribute("Factor",Integer.toString(i))
.addAttribute("Value",Integer.toString(i));
i+=1;
}
The xpr file transform the xml payload in the following ways:
updated the value of the DTOStep node.
The attribute value of DTOStep is autoincremented from 500 each time.
Please assist me.

Answer 1

You need to migrate the complete flow to Mule 4. The file responseStubCannasure.xpr is just a script in MEL (Mule 3 expression language). The extension is irrelevant, it could have been anything. MEL is very similar to Java so you could reuse the logic by encapsulating it into a Java class. You will need to add to the Java code the conversion to DOM4J from the input XML because Mule 4 doesn't support it. Probably is slightly easier to migrate the MEL script to a Groovy script because the basic syntax is very similar and both support scripts. Migrating to Java is just taking the additional steps of encapsulating the script into a method of a class and defining explicitly the types for variables.
Alternatively you could just delete the last 4 operations of the flow and replace them with a DataWeave transformation. Using a recursive function to navigate the keys and value recursively, using a condition to check if we are in the element DTOCoverage, with attribute Status == "Active" and then replace the nested element with the DTOSteps/DTOStep combination. Which is what your script does.
Example:
%dw 2.0
output application/xml
var startingValue=500
fun transformSteps(x, index)=
x filterObject ($$ as String != "DTOSteps") ++
{
DTOSteps: DTOStep #(Order:1, Factor: index + startingValue, Value: index + startingValue, Name:"Final Premiun", Operation:"=", Desc: "Final Premium Desc"): null
}
fun transformCoverage(x, index)=
{
val: x match {
case is Object -> x mapObject
if ($$ as String == "DTOCoverage" and $$.#Status == "Active")
{
DTOCoverage #(( $$.# - "FullTermAmt" ), FullTermAmt: $$$ + startingValue):
transformSteps($, index)
}
else
(($$): transformCoverage($, index+1))
else -> $
},
index: index
}
---
transformCoverage(payload,1).val
This solution doesn't completely resolve the Value and Factor (why two attributes with the same value?) sequential increase. You may need to do an additional transformation, or use Groovy or Java code to renumber them.