Github user markap14 commented on the issue:
https://github.com/apache/nifi/pull/2777
@MikeThomsen @ijokarumawak Hey guys, I'm sorry to chime in a bit late here.
I don't think this is really the approach that we want to take here, though.
What our interface provides currently is a mechanism to pass in the
'coordinates', i.e., the location for finding the data that we want. The
approach here takes this concepts and muddies it by providing arbitrary
key/value pairs that don't make sense for the lookup.
I would propose an alternative approach, which would be to add a new method
to the interface that has a default implementation:
```
default Optional<T> lookup(Map<String, Object> coordinates, Map<String,
String> context) throws LookupFailureException {
return lookup(coordinates);
}
```
Where `context` is used for the FlowFile attributes (I'm referring to it as
`context` instead of `attributes` because there may well be a case where we
want to provide some other value that is not specifically a FlowFile
attribute). Here is why I am suggesting this:
- It provides a clean interface that properly separates the data's
coordinates from FlowFile attributes.
- It prevents any collisions between FlowFile attribute names and
coordinates.
- It maintains backward compatibility, and we know that it won't change the
behavior of existing services or processors/components using those services -
even those that may have been implemented by others outside of the Apache realm.
- If attributes are passed in by a Processor, those attributes will be
ignored anyway unless the Controller Service is specifically updated to make
use of those attributes, such as via Expression Language. In such a case, the
Controller Service can simply be updated at that time to make use of the new
method instead of the existing method.
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