Computed Properties in mapper

Is it possible to have a computed property or maybe multiple names/alias as part of the json mapper ?
Eg. Transformation
```
[{"id" : "someId"}, {"_id" : "sdfdf"}] => [{"id" : "someId"}, {"id" : "sdfdf"}]
```
Above I have 2 objects one with `id` and another with `_id` want to map both to `id` in the resulting object
Also the cases file fullname = firstName + secondName
