Mule 3 retrieving the placeholder value dynamically

Question

I have a use-case that I need to retrieve the value from my properties file but that key should be derived dynamically from my query params.

How to handle this in MEL or Groovy? I am aware it is possible in DW.

Http request
https://localhost:9898/getStore?search=customer.weststore.name

And my placeholders are -

file.properties
customer.weststore.name=TESTING
customer.eaststore.name=IRERRER

So the way I need to access something like this

<set-variable variableName="westDetail" value="#[message.inboundProperites['customer.weststore.name']" doc:name="Variable"/>
<logger message="${westDetail}" level="INFO" /> --> Failed as no placeholder available

When I tried the above it's failing due to no placeholder as "westDetail" available whereas I need the fetch that particular key from the properties file.

This is something related to this article - https://help.mulesoft.com/s/question/0D52T00004mXTQUSA4/dynamically-read-property-values-from-a-properties-file-in-mule but the only solution provided with DW not MEL or Groovy.

How anyone advises, Is it possible?

Answer 1

I understand that the problem is that you want to query the properties by a key that is obtained at execution.

You are doing it incorrectly. ${} is for evaluating the value of a property, which is done at initialization time of the application. You missed that get the actual value in the set-variable.

#[] is for executing a MEL expression, which happens at execution time. flowVars.westDetail is a MEL expression that returns the value of flow variable westDetail. You can't use a MEL expression to evaluate the property placeholder ${}, because they are evaluated at different times.

A solution is to use a Spring bean to store the properties, instead of a configuration properties placeholder. Then you can assign it to a flow variable and access it like a map.

Example:

<spring:beans>
  <spring:bean id="myProperties" class="org.springframework.beans.factory.config.PropertiesFactoryBean">
    <spring:property name="location" value="classpath:items.properties"/>      
  </spring:bean>    
</spring:beans>

<flow name="myFlow">
    <http:listener config-ref="HTTP_Listener_Configuration" path="/" doc:name="HTTP"/>
    <set-variable value="#[app.registry.myProperties]" variableName="props"></set-variable>
    <logger message="a=#[flowVars.props['a']]" level="INFO"/>
</flow>

items.properties:

a=1
b=2
c=3

Output:

a=1