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From "Ryan Blue (JIRA)" <j...@apache.org>
Subject [jira] [Created] (AVRO-1469) Support interchangeable object models
Date Thu, 27 Feb 2014 19:29:20 GMT
Ryan Blue created AVRO-1469:
-------------------------------

             Summary: Support interchangeable object models
                 Key: AVRO-1469
                 URL: https://issues.apache.org/jira/browse/AVRO-1469
             Project: Avro
          Issue Type: New Feature
          Components: java
    Affects Versions: 1.7.6
            Reporter: Ryan Blue


The current way to use a different in-memory representation is to subclass one of the data
modules, like {{GenericData}}, and override the relevant methods. This approach has a couple
of drawbacks:
1. Because Reflect inherits from Generic, both must be subclassed and altered to preserve
the choice between generic records and POJOs. This may have nothing to do with the object
classes being changed (e.g., Map implementation).
2. Replacing the data class tends to also require replacing the DatumReader and DatumWriter
implementation.

>From discussion on a related Kite issue, Doug writes:
bq. It's hard to know up front what bundles of functionality folks will need. We might add
a separate interface that determines the representation of each type (records, maps, arrays,
enums, strings, bytes, fixed, unions, numbers, etc.), then have generic/specific/reflect implementations
for records, collection/array implementations for array, Utf8/String for string, tagged/untagged
unions, etc. Currently we have one big interface (GenericData) for all of these, with a hierarchy
of implementations that provide a few common combinations, but far fewer than are logically
possible.

The use case I'd like to focus on is interchanging both the POJO/record model and the other
objects independently. I think this follows from the distinction between Generic and Reflect
and is a good starting point.



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