Dataweave

Question 1

What is dataweave ?

Answer 1

Dataweave is a mulesoft expression language for accessing and transforming data that travels through a mule application.

Question 2

Define and call a variable ?

Answer 2

%dw 2.0
     var myJson = {"Hello" : "World"}
     var cr=10
     output application/json
     ---
    {
         myObjectVar : myJson,
         price: cr*3
    }

     Output:
     {
          myObjectVar: {"Hello" : "World"},
         price: 30
     }

Question 3

Use a dataweave function in a dataweave variable ?

Answer 3

%dw 2.0
var myJson = {
a: avg([1, 1000]),
b: avg([1, 2, 3])
}
output application/json
---
myJson

Output:

{
“a”: 500.5,
“b”: 2.0
}

Question 4

Read, Transform and select content from an input

Answer 4

%dw 2.0
var myRead = read("red",                "application/xml")
output application/json
---
{  
mySelection : myRead.car
}

Output:

{
  "mySelection": {
    "color": "red"
  }
}

Question 5

What are the sections/parts in Dataweave script?

Answer 5

Header and Body

Question 6

Concatenate Two Strings into a Single String

Answer 6

%dw 2.0
output application/json
—
{ myString: (“hello” ++ “World”) }

Output:
{
“myString”: “helloWorld”
}

Question 7

What does the header contains?

Answer 7

Dataweave declaration : %dw 2.0
..
.
.
.
.
.

Question 8

What is this declaration called ?

output application/json

Answer 8

Output directive

Question 9

Read File Contents with a DataWeave Function

Answer 9

1. Create a file src/main/resources/myjson.json
{
  "hello": "world"
}
2. Dataweave script
%dw 2.0
output application/json
---
readUrl("classpath://myJson.json", "application/json")

3. Output:
   {
   “hello”: “world”
   }

Question 10

Extract only values from key value pairs in json

Answer 10

Use the pluck function 
%dw 2.0
output application/json
---
{
  "0": "a",
  "1": "b",
  "2": "c"
} pluck ((value) -> value)

Output:
[
  "a",
  "b",
  "c"
]

Question 11

What does $$ indicate in map operator

Answer 11

Index of the array

Question 12

What does $ indicate in map operator

Answer 12

The value/data at an index in the array

Question 13

Filter an array with condition value >2
Input:
[9,2,3,4,5]

Answer 13

[9,2,3,4,5] filter (value,index) -> (value > 2)
[9,2,3,4,5] filter ($ >2)
Output:
[9,3,4,5]

Question 14

Filter an array with condition index > 2
Input:
[9,2,3,4,5]

Answer 14

[9,2,3,4,5] filter (value,index -> (index > 2)
[9,2,3,4,5] filter ($$ >2)
Output:
[4,5]

Question 15

Filter an array with condition index > 1 and value <5
Input:
[9,2,3,4,5]

Answer 15

[9,2,3,4,5] filter (($$ > 1) and ($ < 5))
Output:
[3,4]

Question 16

What are these called ?

$$ and $

Answer 16

Anonymous parameters.

These are used in place of named parameters in anonymous function

Question 17

How do you define date and time ?

Answer 17

Enclosed in pipes.
myDate: |2018-12-07|,
myTime: |11:55:56|,
myDateTime: |2018-10-01T23:57:59-03:00|,

Question 18

Object with condition field ?

Answer 18

myObjectWithConditionalField: { a : { b : 1, ( c : 2 ) if true, (d : 4) if false } },

Question 19

Define string as binary

Answer 19

myBinary: “abcd1234123” as Binary

Question 20

What is pluck function and how to use it ?

Answer 20

Pluck function iterates over a json object and can be used to output values into an array.
%dw 2.0
output application/json
---
{
  "0": "a",
  "1": "b",
  "2": "c"
} pluck ((value) -> value)

Output:
[
  "a",
  "b",
  "c"
]

Question 21

Conditional check on a payload

Answer 21

ContainsRequestedItem: myInput.root.order.items contains “3”

Question 22

Get current time ?

Answer 22

currTime: now()

Question 23

Define and call a function ?

Answer 23

fun toUser(obj) = {
firstName: obj.field1,
lastName: obj.field2
}

Question 24

What is the default output directive ?

Answer 24

application/java

Question 25

What can dataweave header contain ?

Answer 25

Declaration ( %dw 2.0)
Import DW function module (import * from dw::core::Arrays)
functions ( fun myFunc(obj) = {fname=obj.field1} )
output directive ( output application/xml )
variables (var myVar = 12.32)
Name spaces (ns ns0 http://abc.com)
Define custom types (type)

Question 26

What are custom types and how to use them in dw script ?

Answer 26

?

Question 27

What are namespaces and how to define and use them in dw script ?

Answer 27

?

Question 28

What is new in DW 2.0 ?

Answer 28

Operators are functions:
DW1 : sizeOf payload filter $.age > 30
DW2: sizeOf(payload filter $.age > 30)

Traits are functions:
DW1 : payload is :empty
DW2: isEmpty(payload)

Type Names:
DW1: payload.foo as :string
DW2: payload.foo as String

Ability to call out to java code

Modules and imports

Question 29

What are standalone and inline DW scripts

Answer 29

Standalone scripts are the one’s that are written in transform component.

Inline DW expressions are to used to transform data in place and dynamically set values of various properties of components such as choice router, set payload or set variable component

Question 30

What is importing modules and how to do it?

Answer 30

DW 2.0 functions are packaged in modules.
Functions in the core (dw::core) are imported automatically.
import dw::core::Strings
import camelize, capitalize from dw::core::Strings
import * from dw::core::Strings

Examples:
%dw 2.0
import dw::core::Strings
output application/json
{ "plural" : Strings::plurarize("box")}

%dw 2.0
import pluralize from dw::core::Strings
output application/json
{ “plural” “ pluralize(“box”) }

Question 31

Give some examples on string manipulation functions?

Answer 31

camelize:
{“a”: camelize(“Customer_first_name”)” O/P “a”: CustomerFirstName

capitalize:
“a” : capitalize(“customer”) O/P “a” : “ Customer”
“b” : capitalize(“customer_first_name”) O/P “b” : “Customer First Name

isLowerCase:
“a” : isLowerCase(“abc”) O/P “a” : true

isUpperCase:
“a” : isUpperCase(“abc”) O/P “a”: false

pluralize:
“a” : pluralize(“box”) O/P “a”: boxes

singularize:
“a”: singularize(“boxes”) O/P “a” : box

Question 32

What are selectors and how to use them?

Answer 32

Selectors allow you to extract data from objects, arrays, variables and payload.

var myObject : { “myKey” : “1234”, “name”: “somebody” }
var myArray: [ {“myKey” : “12345”}, { “name” : “somebody” } ]
—
{
fromObject: myObject.name,
fromArray: myArray.name
}

Output:
{
"fromObject" : somebody,
"fromArray" : [somebody]
}

Question 33

Different selectors?

Answer 33

Single value selector (.myKey)
Multivalue selector (.*)
keyvalue pair (.&myKey)
Decendents(..myKey)
index([])
XML Attribute (.@mykey)
Namespace selector (mykey.#)
Range [index1 to index2]
Selector Modifier (? and !)
Filter selectors ( mykey[?(booleanExpression)])
Metadata Selector (.^someMetadata)