I have a question relating to the DataMapper component and extending the behaviour. I have a scenario where I'm converting one payload to another using the DataMapper. Some of the elements in my source request as strings (i.e. Male, Female) and these values need to be mapped to ID elements, known as enums in the target system. A DBLookup will suffice but because of the structure of enums (a.k.a lookup tables) in the target system I'd need to define multiple DBLookups for the values which need to be changed. So I'm looking to develop a more generic way of performing the mapping. I've two proposals, which I'm currently exploring
1) Use the invokeTransformer default function in to call a custom transformer. i.e.
output.gender = invokeTransformer("EnumTransformer",input.gender);
However, even though my transformer is defined in my flow
<custom-transformer name="EnumTransformer" class="com.abc.mule.EnumTransformer" />
Running a Preview in the DataMapper fails with the following error (in Studio Error Log)
Caused by: java.lang.IllegalArgumentException: Invalid transformer name 'EnumTransformer'
at com.mulesoft.datamapper.transform.function.InvokeTransformerFunction.call(InvokeTransformerFunction.java:35)
at org.mule.el.mvel.MVELFunctionAdaptor.call(MVELFunctionAdaptor.java:38)
at org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.getMethod(ReflectiveAccessorOptimizer.java:1011)
at org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.getMethod(ReflectiveAccessorOptimizer.java:987)
at org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.compileGetChain(ReflectiveAccessorOptimizer.java:377)
... 18 more
As the transformer is scoped to my flow and the datamapper is outside this scope do I assume it is now possible to invoke a custom transformer in a datamapper? Or do I require additional setup.
2) The alternative approach would be to use "global function". I've found he documentation in this area to be quiet weak. The functionality is referenced in the the cheat sheet and there is a [jira]( https://www.mulesoft.org/jira/browse/MULE-6438) to improve the documentation.
Again perhaps this functionality suffers from a scope issue. Questions on this approach is if anyone can provide a HOWTO on calling some JAVA code via MEL from a data mapper script? This blog suggests data mapper MEL can call JAVA but limits it's example to string functions. Is there any example of calling a custom JAVA class / static method?
In general I'm questioning if I am approaching this wrong? Should I use a Flow Ref and call a JAVA component?
Update
It is perfectly acceptable to use a custom transformer from the data mapper component. The issue I was encountering was a Mule Studio issue. Preview of a data mapping which contains a transformer does not work because the mule registry is not populated on the mule context as mule is not running.
In terms of the general approach now that I have realized the DB Lookup can accept multiple input parameters I can use this to address my mapping scenario.
Thanks
Rich
