need clarification on this below key value pairs - mulesoft

Question

Description:
Input should be json object.
Sort the key, value pairs alphabetically on basis of key.
Generate the output as mentioned in the example below.
Example:
Input:
{
"name":"<<your_name>>",
"age":"<<your_age>>",
"city":"<<your_city>>",
"role":"<<your_role>>"
}
Output:
age=<<your_age>>&city=<<your_city>>&name=<<your_name>>&<<your_role>>
Note: Please send the input using postman and your code should work for any number of key, value pairs.

Answer 1

First let me say that if you intend to use the as the query parameters string of an HTTP request it is not a good idea. It would make a lot more sense to use the HTTP Requester to just send each attribute with the requester as a query parameter. It will automatically apply URL encoding and handle the parameters.
Example:
<set-variable value='#[{
name:"<<your_name>>",
age:"<<your_age>>",
city:"<<your_city>>",
role:"<<your_role>>"
}]' doc:name="Set Variable" variableName="person"/>
<http:request method="GET" config-ref="HTTP_Request_configuration" path="/backend" >
<http:query-params><![CDATA[#[vars.person]]]></http:query-params>
</http:request>
See how you just tell it to use the object to generate the query parameters. The output request will be:
GET /backend?name=%3C%3Cyour_name%3E%3E&age=%3C%3Cyour_age%3E%3E&city=%3C%3Cyour_city%3E%3E&role=%3C%3Cyour_role%3E%3E HTTP/1.1
If you absolutely feel that you have to build the query parameters string manually see below.
Example:
%dw 2.0
output application/json
import * from dw::core::URL
---
// it is not recommended to use this, use the HTTP Requester <http:query-params> instead
encodeURI(
payload pluck ((value, key, index) ->
{ key: key, value: value}
)
orderBy( $.key )
reduce ((val, acc = "") ->
acc ++ (if(sizeOf(acc) !=0) "&" else "") ++ val.key ++ "=" ++ val.value)
)