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From "Keegan Witt (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (AVRO-1468) implement interface-based code-generation
Date Fri, 25 Jul 2014 23:32:39 GMT

    [ https://issues.apache.org/jira/browse/AVRO-1468?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14075130#comment-14075130
] 

Keegan Witt commented on AVRO-1468:
-----------------------------------

Would the ability to do polymorphic interface references like this be out of the scope of
this Jira?

{code}
{
  "type": "record",
  "name": "Cat", "namespace":"the.universe",
  "fields": [
    {"name":"name",
     "type":"string"},
    {"name":"collarSize",
     "type":"int"},
    {"name":"aloofness",
     "type":"int"},
  ]
}

{
  "type": "record",
  "name": "Dog", "namespace":"the.universe",
  "fields": [
    {"name":"name",
     "type":"string"},
    {"name":"collarSize",
     "type":"int"},
    {"name":"friendliness",
     "type":"int"},
  ]
}
{code}

{code}
public interface Pet {
  public String getName();
  public void setName(String name);
}

public class Cat implements Pet {
  // ...
}

public class Dog implements Pet {
  // ...
}

public class ExampleUsage {
  public static void main(String[] args) {
    List<Pet> pets = PetUtil.listPets();
    Map<String, Integer> petNames = new HashMap<>();
    for (Pet pet : pets) {
        petNames.put(pet.getname(), pet.getCollarSize());
    }
  }
}
{code}

> implement interface-based code-generation
> -----------------------------------------
>
>                 Key: AVRO-1468
>                 URL: https://issues.apache.org/jira/browse/AVRO-1468
>             Project: Avro
>          Issue Type: New Feature
>            Reporter: Doug Cutting
>
> The current specific compiler generates a concrete class per record.  Instead, we might
generate an interface per record that might be implemented in different ways.  Implementations
might include:
>  - A wrapper for a generic record.  This would permit the schema that is compiled against
to differ from that of the runtime instance.  A field that was added since code-generation
could be retained as records are filtered or sorted and re-written.
>  - A concrete record.  This would be similar to the existing specific.
>  - A wrapped POJO.  The generated class could wrap a POJO using reflection.  Aliases
could map between the schema used at compilation and that of the POJO, so field and class
names need not match exactly.  This would permit one to evolve from a POJO-based Avro application
to using generated code without breaking existing code.
> This approach was first described in http://s.apache.org/AvroFlex



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