使用DataWeave 2.0将XML转换为CSV

Question

I have a person.xml,

<?xml version="1.0" encoding="UTF-8"?>
<person>
    <firstName>First Name</firstName>
    <lastName>Last Name</lastName>
</person

I have person.xsd,

<?xml version="1.0" encoding="UTF-8" ?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="person">
<xs:complexType>
  <xs:sequence>
    <xs:element name="firstName" type="xs:string"/>
    <xs:element name="lastName" type="xs:string"/>
  </xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>

I need to convert it to person.csv,

firstName,lastName
First Name,Last Name

I am using Anypoint Studio 7.3 on windows 10, I am using a Listener, Read (file) xml.

See Transform Message dw below,

%dw 2.0
output application/csv separator=",", header=true
--- 
payload

I am getting the following message on executing the flow,

"Cannot coerce Object { encoding: UTF-8, mediaType: text/xml; charset=UTF-8, mimeType: text/xml, raw: org.mule.weave.v2.el.SeekableCursorStream@2fdc554d } ({person: {firstName: "Shahjahan",lastName: "Ravjee"}} as Object {encoding: "U...) to Array, while writing CSV at payload." evaluating expression: "%dw 2.0
output application/csv separator=",", header=true
--- 
payload
    ".

Answer 1

The problem is, as the error message is stating, you're trying to convert an object into an array. This is a problem because in order to make a CSV, you need an array of arrays, or an array of objects.

You can see if you're currently outputting an object or array by setting your output to application/dw .

%dw 2.0
output application/dw
---
payload

This will give you the following, which as you can see is an object:

{
  person: {
    firstName: "First Name",
    lastName: "Last Name"
  }
}

CSV needs an array, so we'll need to do a little transformation to get it to this:

[
  {
    firstName: "First Name",
    lastName: "Last Name"
  }
]

If you set the following script to output application/dw , you'll see that it outputs the above. At this point, you can be sure you have the correct format needed to create a CSV (array of objects, in this case), so switch it back to output application/csv and you should be good to go:

%dw 2.0
output application/csv
---
payload pluck($)

Answer 2

The following dw seems to have worked like a charm,

  %dw 2.0
    output application/csv headerLineNumber = 0 , header = true
    ---
    [{
        firstName: payload.person.firstName,
        lastName: payload.person.lastName
    }
    ]