Create a message from a collection of collections in MULE ESB - collections

Question

I have a JSON like:
{
"EDITORS" : [{
"EDITOR" : "MCGRAM HILL",
"BOOKS" : [{
"NAME" : "DIFFERENTIAL CALCULUS",
"YEAR" : "1995",
"TIMES_READ" : "135"
}, {
"NAME" : "2012 THE END OF THE WORLD",
"YEAR" : "2012,",
"TIMES_READ" : "56"
}
]
}, {
"EDITOR" : "DEMIDOVICH",
"BOOKS" : [{
"NAME" : "SOME TITTLE",
"YEAR" : "1975,",
"TIMES_READ" : "154"
}, {
"NAME" : "THE LITTLE PRINCE",
"YEAR" : "1987,",
"TIMES_READ" : "57"
}
]
}, {
"EDITOR" : "ADRIAN LOPEZ ASC.",
"BOOKS" : [{
"NAME" : "SOMETHING",
"YEAR" : "2008,",
"TIMES_READ" : "10"
}
]
}
]
}
I need to transform it into an output like:
payload[0]= The editor MCGRAM HILL has:
The book DIFFERENTIAL CALCULUS published in 1995 has been readed 135 times.
The book 2012 THE END OF THE WORLD published in 2012 has been readed 56 times.
payload[1]= The editor DEMIDOVICH has:
The book SOME TITTLE published in 1975 has been readed 154 times.
The book THE LITTLE PRINCE published in 1987 has been readed 57 times.
payload[2]= The editor ADRIAN LOPEZ ASC. has:
The book SOMETHING published in 2008 has been readed 10 times.
So far I transform the JSON to an Java Object, then use a foreach scope with the collection #[payload.EDITORS]
Inside the foreach I create a variable Intro = "The editor #[payload.EDITOR] has:"
And after that I'm lost.
I have tried to set payload to #[payload.BOOKS] and then use another foreach but this only shows the last book, and have also try Collection Aggregator but don't know what to write in "Message info Mapping".
How can I accomplish the required output?
Any help could be greatly appreciated, thanks in advance.

Answer 1

Try following with dataweave
%dw 1.0
%output application/json
---
{(payload.EDITORS map ((data, index) -> {
payload : "The editor " ++ data.EDITOR ++ " has:\r\n" ++
{(data.BOOKS map {
pqr : "The book " ++ $.NAME ++ " published in " ++ $.YEAR ++ " has been readed " ++ $.'TIMES_READ' ++ " times."
})} pluck $ joinBy "\r\n"
}))} pluck $
Json Output for reference. You can transform to java to get desired output.
[
"The editor MCGRAM HILL has:\r\nThe book DIFFERENTIAL CALCULUS published in 1995 has been readed 135 times.\r\nThe book 2012 THE END OF THE WORLD published in 2012, has been readed 56 times.",
"The editor DEMIDOVICH has:\r\nThe book SOME TITTLE published in 1975, has been readed 154 times.\r\nThe book THE LITTLE PRINCE published in 1987, has been readed 57 times.",
"The editor ADRIAN LOPEZ ASC. has:\r\nThe book SOMETHING published in 2008, has been readed 10 times."
]
Hope this helps.

Answer 2

IMHO, you don't need to set payload inside the foreach scope.
I tried the following configuration and it produces a list of string which containing those message. I think you can modify the last message processor to display the expected output (e.g.: add another foreach or expression to extract the message from the final payload/ArrayList).
<json:json-to-object-transformer returnClass="java.util.Map" doc:name="JSON to Object"/>
<set-variable variableName="messageMapping" value="#[new java.util.ArrayList()]" doc:name="Variable"/>
<foreach collection="#[payload.EDITORS]" doc:name="For Each">
<set-variable variableName="messageEditor" value="The editor #[payload.EDITOR] has: " doc:name="Variable"/>
<foreach collection="#[payload.BOOKS]" doc:name="For Each">
<expression-transformer expression="#[flowVars.messageEditor += "\r\nThe book " + payload.NAME + " published in " + payload.YEAR + " has been readed " + payload.TIMES_READ + " times."]" doc:name="Expression"/>
</foreach>
<expression-transformer expression="#[flowVars.messageMapping.add(flowVars.messageEditor)]" doc:name="Expression"/>
</foreach>
<set-payload value="#[flowVars.messageMapping]" doc:name="Set Payload"/>
<logger message="#[payload]" level="INFO" doc:name="Logger"/>
If you prefer to use DataWeave, then you can use the following code:
%dw 1.0
%output application/java
---
payload.EDITORS map (
'The editor ' ++ $.EDITOR ++ ' has:\r\n' ++
($.BOOKS map (
'The book ' ++ $.NAME ++ ' published in ' ++ $.YEAR ++ ' has been readed ' ++ $.TIMES_READ ++ ' times.'
) joinBy '\r\n')
)

Answer 3

Dataweave doens't feel like the right approach, specially because the output is plain txt.
Personally I'd probably use json-to-object (see below) and parse template.
<json:json-to-object-transformer returnClass="java.util.Map" />