The document discusses the DataWeave language, which allows transforming data between different formats like XML, JSON, CSV. It describes the structure of a DataWeave file with a header section containing directives, a body section defining the output, and an optional separator. An example is provided to transform JSON input to XML output. Key points about directives, input/output types, and the three basic DataWeave data types are also summarized.

2.  The Data Weave Language is a powerful
template engine that allows you to transform
data to and from any kind of format (XML,
CSV, JSON, Pojos, Maps, etc).

3.  The Header, which defines directives
(optional)
 The Body, which describes the output
structure
 The two sections are delimited by a
separator, which is not required if no header
is present. The separator consists of three
dashes: "---"

4.  This code describes a conversion from a JSON
input to an XML output:
%dw 1.0
%input application/json
%output application/xml
---
{
user: {
name: payload.user_name,
lastName: payload.user_lastName
}
}

5.  If Output is other than Json , then just replace
Json to required form like XML, CSV etc. in
the header part :
%input application/json
• Payload attribute is the input data and
each field should be separated by
comma :
name: payload.user_name,
lastName: payload.user_lastName

6. <?xml version="1.0" encoding="UTF-8"?>
<user>
<name> userNameFromPayload </name>
<lastName>
lastNameFromPayload</lastName>
</user>

7.  The sample output for the example shown
above looks like : (Json format)
{
"user_name": “userNameFromPayload",
"user_lastName": " lastNameFromPayload“
}

8.  The DataWeave header contains the directives,
which define high level information about your
transformation. The structure of the Header is a
sequence of lines, each with its own Directives.
The Header is terminated with '---'.
 All directives are declared on the header section
of your DataWeave document and act upon the
entire scope of it.
 Directives are a mechanism to declare variables
and constants and namespace aliases which need
to be referenced in the Document. They are also
needed to declare the type of the output of your
transform.

9.  DataWeave version
 Input types and sources
 Output type
 Namespaces to import into your transform
 Constants that can be referenced throughout
the body
 Functions that can be called throughout the
body

10. Version Directive : Namespace Directive :
 Through this directive,
you specify the version
of the DataWeave
syntax that is used to
interpret the
transformation.
 coded as : %dw 1.0
 This directive associates
an alias with its
subsequent URI. The
directive is relevant only
when either the input or
the output is of type
XML.
 Coded as : %namespace
mes
http://www.mulesoft.co
m/anypoint/SOA/messag
e/v1.0

11. Input Directive : Valid input types are :
 Inputs are declared by
assigning a name and a
content type. You can
then refer to them in any
part of the DataWeave
body through the names
defined in the directive.
 Coded as : %input
payload application/xml
 application/json
 application/xml
 application/java
 application/csv
 application/dw
 text/json
 text/xml
 text/csv

12.  When defining an input of type CSV, there are a
few optional parameters you can add to the input
directive to customize how the data is parsed.
These are not defined in the DataWeave script
but on the Mule XML code, in the Transform
Message XML element.
 There are two ways to achieve this :
 Manually add the attributes to the project’s XML
 graphical interface, by selecting the element from
the tree view in the input section and clicking the
gear icon

13. Output Directive : Valid output types are :
 The Output Directive
specifies what the output
type is in a
transformation, which is
specified using
content/type. Only one
output can be specified,
the structure of this
output is then defined in
the DataWeave body.
 Coded as :
%output application/xml
 application/json
 application/xml
 application/java
 application/csv
 application/dw
 text/json
 text/xml
 text/csv

14.  Whenever the output is of XML or JSON type and has null
values in its elements or attributes, you can specify
whether this generates an outbound message that
contains fields with "null" values, or if these fields are
ignored entirely. This can be set through an attribute in
the output directive named skipNullOn, which can be set
to three different values: elements, attributes,
or everywhere.
 Like : %output application/xml skipNullOn="everywhere“
When set to:
 elements: A key:value pair with a null value is ignored.
 attributes: An XML attribute with a null value is skipped.
 everywhere: Apply this rule to both elements and
attributes.

15.  DataWeave uses three basic data types:
Objects, Arrays, and Simple Types, the
execution of a DataWeave transformation
always produces one of these three types of
data.
 This expression can be built using any of the
following elements:
 Objects
 Arrays
 Simple literals
 Variable and Constant references

16.  Input
<?xml version="1.0" encoding="UTF-8"?>
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

17. %dw 1.0
%output application/dw
---
payload
Output :
{
note: {
to: "Tove",
from: "Jani",
heading: "Reminder",
body: "Dont forget me this weekend!“
}
}

18. Still many to learn … Stay tuned!!!!!!!!!!!!