DynamoDB Enhanced Client Polymorphic Types

We should support reading/writing base types using the DynamoDB Enhanced Client.

Potential syntax/example (not yet implemented):

@DynamoDbBean
@DynamoDbSubtypes({Employee.class, Customer.class})
public abstract class Person {
    @DynamoDBHashKey
    private long id;
    private String name;
}

@DynamoDbBean
private class Employee extends Person {
}

@DynamoDbBean
private class Customer extends Person {
}

DynamoDbEnhancedClient client = DynamoDbEnhancedClient.create();
DynamoDbTable<Person> people = client.table("people", TableSchema.fromBean(Person.class));

Employee bob = new Employee();
bob.setId(1);
bob.setName("Bob the Builder");

Customer lfh = new Customer();
lfh.setId(2);
lfh.setName("Low Flying Hawk");

people.putItem(bob);
people.putItem(lfh);

assertThat(people.getItem(Key.builder().partitionValue(1).build())).isInstanceOf(Employee.class);
assertThat(people.getItem(Key.builder().partitionValue(2).build())).isInstanceOf(Customer.class);

[bmaizels]

For anyone tracking this issue, I have created a PR with an implementation that I hope addresses the needs identified here. It will probably be at least a couple of weeks before this gets final approval and makes it into the release, so it would be extremely valuable if people could try it out and see if there are any rough edges or improvements I could make before it becomes difficult to change it after release. It’s a complex change, so lots of scope for not getting things quite right. Instructions on how to declare subtypes are in the new README.md file in the dynamodb-enhanced module under the section titled ‘Using subtypes…’. https://github.com/aws/aws-sdk-java-v2/pull/2861

[gakinson]

This would be super useful!