Dataweave passing varaible to url mulesoft

Question

I'm trying pass the queryParams dynamically to request depending from user what put in postman. Here is the transform message with variable name jql (this variable I would like then pass in url)

<ee:transform doc:name="Transform Message" >
            <ee:message>
            </ee:message>
            <ee:variables>
                <ee:set-variable variableName="queryParams" ><![CDATA[
{
    "demo" : attributes.queryParams['demo'] default "",
        "demo2": attributes.queryParams['demo2'] default "",
         "demo3" :attributes.queryParams['demo3'] default ""
}
                
]]></ee:set-variable>
    <ee:transform doc:name="Transform Message"  >
            <ee:message >
            </ee:message>
            <ee:variables >
                <ee:set-variable variableName="jql" ><![CDATA[
if(vars.queryParams.demo != null and vars.queryParams.demo2 == null and vars.queryParams.demo3 == null)
    "demo= " ++ vars.queryParams.demo 
else if(vars.queryParams.demo2 != null and vars.queryParams.demo3 == null and vars.queryParams.demo == null)
    "demo2 = " ++ vars.queryParams.demo2 
else if(vars.queryParams.demo != null and vars.queryParams.demo2 != null and vars.queryParams.demo3 == null )
"demo= " ++ vars.queryParams.demo ++ " and demo2 = " ++ vars.queryParams.demo2 

]]></ee:set-variable>
            </ee:variables>
        </ee:transform>
        <http:request method="GET" doc:name="Request"  config-ref="HTTP_Request_configuration" path="/demo/search">
            <http:query-params><![CDATA[#[output application/java
---
{
    "jql" : vars.jql
}]]]></http:query-params>
        </http:request>

And for example if user put only parameter demo I would like only this "demo = demo" etc.

In this case I got 400 like this:

Message               : HTTP GET on resource 'https://demo/search' failed: bad request (400).
Element               : searchForIssuesUsingJQL/processors/2 @ jira:jira.xml:160 (Request)
Element DSL           : <http:request method="GET"
 doc:name="Request"  config-ref="HTTP_Request_configuration" path="demo/search">
<http:query-params>#[output application/java
---
{
    "jql" : vars.jql
}]</http:query-params>
</http:request>
Error type            : HTTP:BAD_REQUEST

Answer 1

That's not a good way to implement it and it doesn't even cover all possible cases. Better make it dynamic. Let's convert vars.QueryParams into a list for easier manipulation and then reduce it into a single strings, adding " and " to separate elements when the accumulator is not empty:

vars.queryParams
    filterObject (sizeOf($) > 0)
    pluck ((value, key, index) -> {k: key, v:value})
    map ($.k ++ "=" ++ $.v)
    joinBy  " and "

With this method you don't even need to know if it contains a specific string.