Reading a YAML file in Mule 4

Question

I have defined following YAML properties file in Mule.

YAML properties File

table:
  "customers": 
    name: customerID
  "orders": 
    name: ordersDateMin,orderDateMax

I know that to get the name I should use "#[p('table.customers.name')].

What I want to know, is there any way to get the key by passing .name, something like table.key or table.$ . I mean if I pass customerID, I should get the key "customers". Similarly if I pass orderDateMin,orderDateMax it should return "orders".

Is it possible?

Thanks in advance

OK I think I understand what you are asking. There is no easy way to do a reverse lookup of a property value and get the field(s). What you can do is read the file using a DW expression like this: readUrl("classpath://properties.yaml","application/yaml") and then write code to search for the value and get the field(s). — George
I did amend the answer below to reflect my newfound understanding of your question :). Just look at the code below and see if is it what you need. — George
Why not just create another map, with the possible ".names" that map to their respective keys in the table map. — Zingers

George George · Accepted Answer · 2020-06-20T19:15:10

Try this:

%dw 2.0
output application/dw
var props = readUrl("classpath://properties.yaml","application/yaml")
var v = "customerID"

var leafsReversed = (o: Object, r: Object = {}) -> o match {
    case is Object -> r ++ (
        $ mapObject ( 
            (v,k,i) -> if (v["name"] is String) ({(v["name"]):k}) else leafsReversed(v,r)
        )
    )
    else -> r
}

---
[props,leafsReversed(props)]

This is a non-trivial problem with a non-trivial solution. leafsReversed is a recursive function that looks for <field>.name: <value> sequences and tests if the value is a string, if it is then it will create a key,value pair of <value>: <field>. Now you have a map and you can perform lookups.

My advise to you is find another way.

Your property file content is malformed, it does not work as presented above, I changed it to the following for my tests:

table:
  customers: 
    name: "customerID"
  orders: 
    name: "ordersDateMin,orderDateMax"

Here's the Mule Configuration file contents:

<?xml version="1.0" encoding="UTF-8"?>

    <mule xmlns:http="http://www.mulesoft.org/schema/mule/http" xmlns:ee="http://www.mulesoft.org/schema/mule/ee/core"
        xmlns="http://www.mulesoft.org/schema/mule/core"
        xmlns:doc="http://www.mulesoft.org/schema/mule/documentation" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.mulesoft.org/schema/mule/core http://www.mulesoft.org/schema/mule/core/current/mule.xsd
    http://www.mulesoft.org/schema/mule/ee/core http://www.mulesoft.org/schema/mule/ee/core/current/mule-ee.xsd
    http://www.mulesoft.org/schema/mule/http http://www.mulesoft.org/schema/mule/http/current/mule-http.xsd">
        <configuration-properties doc:name="Configuration properties" doc:id="4683e6d8-ad4d-453b-9f1c-19949241c336" file="properties.yaml" />
        <http:listener-config name="HTTP_Listener_config" doc:name="HTTP Listener config" doc:id="dd84777d-25b1-4e42-870b-8e7745689041" >
            <http:listener-connection host="0.0.0.0" port="8081" />
        </http:listener-config>
        <flow name="yaml-propsFlow1" doc:id="62367531-86df-4383-ac60-294a3ae58043" >
            <http:listener doc:name="Listener" doc:id="b1aae490-cfbb-49d9-8216-33e55607f1f2" config-ref="HTTP_Listener_config" path="/"/>
            <ee:transform doc:name="Transform Message" doc:id="63e74066-128f-464d-94f3-646872dfbb6f" >
                <ee:message >
                    <ee:set-payload ><![CDATA[%dw 2.0
    output application/json
    var props = readUrl("classpath://properties.yaml","application/yaml")
    var v = "customerID"
    
    var leafsReversed = (o: Object, r: Object = {}) -> o match {
        case is Object -> r ++ (
            $ mapObject ( 
                (v,k,i) -> if (v["name"] is String) ({(v["name"]):k}) else leafsReversed(v,r)
            )
        )
        else -> r
    }
    
    ---
    [props,leafsReversed(props)]]]></ee:set-payload>
                </ee:message>
            </ee:transform>
        </flow>
    </mule>

Reading a YAML file in Mule 4

1 Answers