MCDLevel1Fundamentals

Question 1

how do you define function in dw 2, whats keyword?

Answer 1

TODO: there are more ways here https://docs.mulesoft.com/dataweave/2.3/dataweave-functions

its "fun" like in
fun myFunction(param1, param2, ...) =

Question 2

whats @ used for in dw? and how does it work given. Consider

%dw 2.0 var myVar = read(‘

SomeBrand ‘,

‘application/xml’)

output application/json

{ item: [ { “type” : myVar.product.@.”type”,

“name” : myVar.product.brand,

“attributes”: myVar.product.@ } ] }

Answer 2

XML Attribute Selector (.@myKey)

@, .@keyName

String value of the selected attribute’. Pay attention when something comes after @ vs nothing. .@ take all attributes and represent it as object and not array.

{
“item”: [
{
“type”: “electronic”,
“name”: “SomeBrand”,
“attributes”: {
“id”: “1”,
“type”: “electronic”
}
}
]
}

Question 3

type of queues in Anypoint MQ?j

Answer 3

1) Standard queue

These queues don’t guarantee a specific message order. Standard queues are the best fit for applications in which messages must be delivered quickly.

Anypoint MQ supports up to 120,000 in-flight messages per standard queue.

2) FIFO (first in, first out) queue

These queues ensure that your messages arrive in order. FIFO queues are the best fit for applications requiring strict message ordering and exactly-once delivery, but in which message delivery speed is of less importance. See FIFO Queues.

Anypoint MQ supports 10 in-flight messages per message group in a FIFO queue. Anypoint MQ doesn’t limit the number of message groups in a FIFO queue.

Question 4

1) What DataWeave 2.0 type can be used as input to a mapObject operation? 2) Whats output given

%dw 2.0
output application/json
—
{“a”:”b”,”c”:”d”} mapObject (value,key,index) -> { (index) : { (value):key} }

Answer 4

1) Object (not map or array or anything)
2) { “0”: { “b”: “a” }, “1”: { “d”: “c” } }
Obs! pay attention to the order of value, key, index
as it can be shuffled on the exam. Remember it as V.K.I , sounds almost like BMI.

Question 5

what reserved property can be defined and used in a mule application to allow an https listener be accessed by external clients after its deployed to cloudhub?

Answer 5

${https.port}

Question 6

when calling endpoint like this, how is dw looking query params up? e.g. http://localhost:8081/retrieveQueryParams?Name=John&EmpId=123

Answer 6

%dw 2.0
output application/json
—
{
“Name”:attributes.queryParams.Name,
“EmployeeId”:attributes.queryParams.EmpId
}

Question 7

when calling endpoint and using uri params, how are they looked up then?

Answer 7

[attributes.uriParams.name]

Question 8

how is mule 3 #[flowVars.varName] replaced in mule 4?

Answer 8

[vars.varName]

Question 9

how is mule 3 #[message.inboundProperties.’http.version’] replaced in mule 4?

Answer 9

…in a Transform message:

if (attributes.headers[‘keyname’] != null and attributes.headers[‘keyname’] != “”) attributes.headers[‘keyname’] as String else null

or directly use this in a log:

attributes.headers[‘keyname’]

Question 10

trait name for specifying client id in raml?

Answer 10

client-id-required
https://docs.mulesoft.com/api-manager/2.x/prepare-raml-task

Question 11

hur placerar man query parametrar, vad heter den och vilka attribut har de?

Answer 11

/books:
/{bookTitle}
get:
queryParameters:
author:
displayName: Author
type: string
description: An author’s full name
example: Mary Roach
required: false
publicationYear:
displayName: Pub Year
type: number
description: The year released for the first time in the US
example: 1984
required: false
put:
queryParameters:
access_token:
displayName:

Question 12

is this removing one array from another or removing elements of the array element?

%dw 2.0
output application/json
—
([0, 1] – [0, 2])

Answer 12

//Elements due to minus minus. Result is single element in the first array

[
1
]

Question 13

what comes first in a filter operation, index or value?

Answer 13

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

Question 14

how can you access header, and it doesnt look like attributes.uriParams.X or attributes.queryParams.X or similar?

Answer 14

attributes.header[‘user-agent’]

Question 15

what does #[payload.*name] and #[payload..name] have in common? and the difference?

Answer 15

common: both return Array with values of key:value pairs
difference: the .* is multi value selector while .. is Descendants selector

Question 16

What does this Descendants selector return?

%dw 2.0
output application/xml
ns html http://www.w3.org/TR/html4/
ns furniture https://www.w3schools.com/furniture
—
root: {
b: payload.root.furniture#table..name
}

given: TODO: fix pic

Answer 16

just like Single level Explicit Selector, or the Indexed Selector, the Descendants Selector returns the value of the key:value pair that matches the expression.

Question 17

What does this Multivalue selector return?

%dw 2.0
output application/json
—
payload.users.*user

and given input:

Answer 17

Multi value selector can either be applied over an :object or an :array.

[“Mariano”, “Martin”, “Leandro”]

Question 18

what does this produce
contains(“names”, “name”)
“nameing” contains “name”

Answer 18

true,
true

Question 19

mapObject, whats the output?
pay attention its not an array

%dw 2.0
output application/json
—
{“a”:”b” , “c”:”d”} mapObject (value,key,index) -> { (index) : { (value):key} }

Answer 19

{ “0”: { “b”: “a” }, “1”: { “d”: “c” } }

Question 20

what to do when backpressure error arises?

Answer 20

https://help.mulesoft.com/s/article/Dealing-with-MULE-FLOW-BACK-PRESSURE-error

Question 21

what does zip operator do in dataweave?

Answer 21

Merges elements from two arrays into an array of arrays.

%dw 2.0
output application/json
—
[0,1] zip [“a”,”b”]

result in

[[0,”a”], [1,”b”] ]

Question 22

What is the value of the stepVar variable after the processing of records in a Batch Job? P.s. read the chapter about batch jobs

Answer 22

null

Question 23

semantic versioning?

Answer 23

https://docs.mulesoft.com/exchange/to-change-raml-version

Major versions = first digit in 1.2.3

When introducing a change in the structure of the API that requires the user of the API to adapt the interface on the consumer side, such as a new required operation argument

Minor versions

When introducing a backward compatible change to the API that does not require an API user to change, such as a new optional element

Patch versions

When introducing a backward compatible bug fix or documentation update

Question 24

Scatter-Gather sends the event to each route concurrently and returns a collection of all results. What is the final output of the Scatter-Gather?

Answer 24

e.g. like this:

{
“0”: {
“inboundAttachmentNames”: [],
“exceptionPayload”: null,
“inboundPropertyNames”: [],
“outboundAttachmentNames”: [],
“payload”: “”,
“outboundPropertyNames”: [],
“attributes”: {
“headers”: {
“user-agent”: “PostmanRuntime/7.22.0”,
“accept”: “*/*”,
“cache-control”: “no-cache”,
“postman-token”: “47e20bb3-3726-4437-8b86-8ef55cd27d71”,
“host”: “localhost:8081”,
“accept-encoding”: “gzip, deflate, br”,
“connection”: “keep-alive”
},
“clientCertificate”: null,
“method”: “GET”
}
},
“1”: {
“inboundAttachmentNames”: [],
“exceptionPayload”: null,
“inboundPropertyNames”: [],
“outboundAttachmentNames”: [],
“payload”: “”,
“outboundPropertyNames”: [],
“attributes”: {
“headers”: {
“user-agent”: “PostmanRuntime/7.22.0”,
“accept”: “*/*”,
“cache-control”: “no-cache”,
“postman-token”: “47e20bb3-3726-4437-8b86-8ef55cd27d71”,
“host”: “localhost:8081”,
“accept-encoding”: “gzip, deflate, br”,
“connection”: “keep-alive”
},
“clientCertificate”: null,
“method”: “GET”
}
}
}

Question 25

how do you format currency String in dataweave and what parenthesis type do you use for formatting?

Answer 25

payload map {
‘price’ : $.price as String {format: “£#,###.00”}
}

Question 26

Provided this is json input:
[
{ “symbol”: “Krona” }
]

and below is transformation, what is the outcome exactly and why?

%dw 2.0
output application/json
—
payload map {
‘code’ : lower($.symbol)
}

Answer 26

[
{
“code”: “krona”
}
]

because

1) The map function transforms data
2) It iterates over the elements in an array
3) It applies a transformation to each element
4) Applies only to array input

and most importan!!! : It can only output an array

Question 27

Do we need to import functions that reside in dw::core?
e.g.

%dw 2.0
import dw::core::Strings
fun capitalizeKey(value:String) = Strings::capitalize(value) ++ “Key”
—
payload mapObject ((value, key) ->
{
(capitalizeKey(key as String)) : value
}
)

Answer 27

yes we do, otherwise we get

Unable to resolve reference of: Strings::capitalize.

7| fun capitalizeKey(value:String) = Strings::capitalize(value) ++ “Key”
^^^^^^^^^^^^^^^^^^^
Location:
main (line: 7, column:35)

Question 28

if i have a dataweave function in src/main/resources/modules/MyModule.dwl then how do i import in in my dataweave?

Answer 28

import modules::MyModule

See https://developer.mulesoft.com/learn/dataweave/ for details. P.s. it seems we just add another ::nextLevel if nextLevel was a catalogue under modules containing MyModules.dwl instead

Question 29

can you import variable and function from you dw script? can you alias those?

Answer 29

yes, given custom module:
%dw 2.0
fun myFunc(name:String) = name ++ “_”
var myVar = “Test”

i would import and alias and use it like this

%dw 2.0
import myFunc as appendDash, myVar as weaveName from modules::MyModule
var myVar = “Mapping”
output application/json
—
appendDash(“dataweave”) ++ weaveName ++ “_” ++ myVar

Question 30

when you see a validate element in the flow, like “validation:is-blank-string”, will it throw exception if is a not empty?

Answer 30

yes, here is curl followed by the result
curl -id “test” http://localhost:8081/sp

HTTP/1.1 500 Server Error
Content-Type: text/plain; charset=UTF-8
Content-Length: 29
Date: Wed, 17 Nov 2021 21:15:34 GMT
Connection: close

whatever validate message!!!

Question 31

name 3 things you use Api manager for except the usual:

• Create and deploy API proxies.
• Define SLA tiers and apply runtime policies

Answer 31

– Approve, reject, or revoke access to APIs by clients
– Promote managed APIs between environments
– Review API analytics

Question 32

what is attribute selector?

Answer 32

and to select it

payload.user.@name

See https://docs.mulesoft.com/dataweave/2.2/dataweave-selectors

Question 33

what does it mean to select EACH, i mean EACH descendant for this and whats the expression? how many childs will it be?

Weave

BAT

BDD

Answer 33

it should be 4 nodes and 3 single strins

%dw 2.0
output application/json
—
payload..

and output is

[
{
“user”: {
“name”: “Weave”,
“user”: {
“name”: “BAT”,
“user”: {
“name”: “BDD”
}
}
}
},
{
“name”: “Weave”,
“user”: {
“name”: “BAT”,
“user”: {
“name”: “BDD”
}
}
},
“Weave”,
{
“name”: “BAT”,
“user”: {
“name”: “BDD”
}
},
“BAT”,
{
“name”: “BDD”
},
“BDD”
]

Question 34

check out do syntax with — in the middle of delclaration, whats allowed in terms of scoping, imports etc

Answer 34

?

Question 35

whats another special thing about .. operator?

Answer 35

The DataWeave script uses .. to select the values of all FIRST, not any but FIRST, name elements from the input payload and output those values into a JSON array. E.g.
payload..name for

Weave

BAT
Munit

BDD

gives

[
“Weave”,
“BAT”,
“BDD”
]

Question 36

does single quotes work as good as doublequotes in dataweae? e.g.
payload.root.h#’$(payload.root.@ref)’
vs
payload.root.h#”$(payload.root.@ref)”

Answer 36

yes, they do

Question 37

what is this selector called and what does it produce?

Given

Mariano
Martin
Leandro
Admin
org_owner

and dataweave:

%dw 2.0
output application/xml
—
{
users: payload.users.&user
}

Answer 37

its called Key-Value Pair Selector (.&myKey)

Mariano
Martin
Leandro

Question 38

whats the difference between Custom Dataweave “Mapping File” and “Mapping Module”

Answer 38

Mapping file looks like normal mapping stored in a separate file. Given your mapping file look like:

%dw 2.0
import dw::core::Strings
fun capitalizeKey(value:String) = Strings::capitalize(value) ++ “Key”
—
payload mapObject ((value, key) ->
{
(capitalizeKey(key as String)) : value
}
)

then you can use it like these:

%dw 2.0
import modules::MyMapping
output application/json
—
MyMapping::main(payload: { “user” : “bar” })

See https://docs.mulesoft.com/dataweave/2.4/dataweave-create-module

Question 39

how can dw “mapping module” look like ?

Answer 39

e.g. :

%dw 2.0
fun myFunc(myInput: String) = myInput ++ “_”
var name = “MyData”
ns mynamespace http://acme.com/bar

see See https://docs.mulesoft.com/dataweave/2.4/dataweave-create-module

Question 40

what are the several ways to import mapping module?

Answer 40

1) Import the module, for example: import modules::MyModule. In this case, you must include the name of the module when you call the element (here, a function) in it, for example: 
MyModule::myFunc. 

2) Import all elements from the module, for example: import \* from modules::MyModule. In this case, you do not need to include the name of the module when you call the element. For example: 
myFunc("dataweave") ++ "name" works. 

3) Import specific elements from a module, for example: import myFunc from modules::MyModule. In this case, you do not need to include the name of the module when you call the element. For example: myFunc("dataweave") ++ "name" works. You can import multiple elements from the module like this, for example: 
import myFunc someOtherFunction from modules::MyModule (assuming both myFunc and someOtherFunction are defined in the module).

Question 41

when you want to have map operation as a node value like trains: ….something map operation here …
what are the parentheses you use?

Answer 41

When mapping array elements (JSON or JAVA) to XML, wrap the map operations in {(..)} e.g.
trains: {( alexMap map ((something, index) -> train : { ..

Question 42

whats important to remember about scope of foreach?

Answer 42

changes made to payload in for each loop are not available outside for each scope. delcaring/incrementing variable is fine though

Question 43

For each method of the RAML specification , what does the REST connect module provide?

Answer 43

For each method of the RAML specification , REST connect module provide an OPERATION, not a flow. Think how it looks in the palette! And dont forget The Exchange backend uses REST Connect to transparently convert a REST API specification to a Mule 3 and Mule 4 connector.

Question 44

A Scatter-Gather processes three separate HTTP requests. Each request returns a Mule event with a JSON payload. What is the final output of the Scatter-Gather?

Answer 44

An object containing Mule event objects, not payload, not messages, but event objects

Question 45

An SLA based policy has been enabled in API Manager. What is the next step to configure API proxy to enforce new SLA policy?

Answer 45

Add required headers to RAML specification and redeploy new API proxy

Question 46

By default , what happens to a file after it is read using an FTP connector Read operation

Answer 46

The file stays in the same folder unchanged

Question 47

What payload is returned by a Database SELECT operation that does not match any rows in database?

Answer 47

Empty array

Question 48

Is this a working declaration: ?

%dw 2.0
output application/json
fun createUserData(name, countryCode : String = “US”) = { “User name” : name, “Location”: countryCode}
—
[createUserData(“Cristian”, “AR”), createUserData(“Max The Mule”)]

Answer 48

yes

Question 49

Which one will be called?

%dw 2.0
output application/json

fun toUpper(a: String) = upper(a)
fun toUpper(a: Any) = null
—
toUpper(“hi!”)

Answer 49

the first one

Question 50

What is the default port used by Mule application debugger configuration in Anypoint Studio?

Answer 50

6666

Question 51

Does syntax with wildcard like /mypath/* work both in http listener and http listener configurations?

Answer 51

No, Please note wildcards wont work in HTTP Listener configurations. They will work only when you configure path in HTTP Listener

Question 52

what is the result of this?

%dw 2.0
output application/json
—
([0, 1] + [0, 2])

Answer 52

//second array injected inside like if its an element

[
0,
1,
[
0,
2
]
]

Question 53

Result 20231201: pass., 4-5 out of max 8 questions failed. questions i wondered:
1)batch steps does not modify payload right. what are those stats in the end then when printing payload. stepsvar in the end?
2) does calling another non-private flow follow same rules like calling private flow? when it comes to err handling, attribs, etc?