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https://issues.apache.org/jira/browse/AVRO-2621?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16973616#comment-16973616
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Cherry Development commented on AVRO-2621:
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I have this working. It was a very small and simple change. Before I attempt to
submit a patch I'd appreciate any sort of feedback about if this is the right
way to go about solving this issue.
> Practical CustomConversions with SpecificCompiler and Maven
> -----------------------------------------------------------
>
> Key: AVRO-2621
> URL: https://issues.apache.org/jira/browse/AVRO-2621
> Project: Apache Avro
> Issue Type: Improvement
> Components: java
> Reporter: Cherry Development
> Priority: Major
> Labels: maven
>
> So, as seen in AVRO-2498 we now have the ability in 1.9, at least using the
> Maven tools, to have generated classes with a field of type UUID. For some
> background, the secret sauce to get this working is:
> * Set the logicalType of the field to 'uuid' and type to 'string'
> * In the maven plugin configuration, add an item to <customConversions> with
> the value org.apache.avro.Conversions$UUIDConversion
> I attempted this with a custom type of my own (in this case, joda Money)
> first by implementing a CustomConversion<Money> class that created a new
> LogicalType called "money". This did not work, though, because although the
> maven mojo correctly added the CustomConversion to the SpecificCompiler, when
> the compiler parses the schema and sees the logicalType of type "money", it
> attempts to look up the LogicalType from LogicalTypes the LogicalType is not
> registered and it ignores it, which causes the field within the Schema to not
> have a logicalType. Without a logicalType, the compiler does not consider it
> a "UsedConversionClass" (see SpecificCompiler.getUsedConversionClass()) and
> they velocity template doesn't write the class with the custom field type.
> Trying to be clever, I attempted to work around this by putting a static
> initializer in my CustomConversion class which called
> LogicalTypes.register(). Unfortunately for me, the maven plugin doesn't load
> any of the classes specified in <customConversions> until AFTER it has parsed
> a schema.
> Obviously, putting a static initializer inside of a CustomConversion should
> not be part of a solution to this issue, but I propose a very simple solution:
> * Add a logicalTypes property to AbstractAvroMojo, with items of a new type,
> LocalTypeDefinition. That type will have a name and a logicalTypeFactory.
> * Upon startup of the mojo, iterate through each item and call
> LogicalTypes.register() on each, passing the indicated name and a new
> instance of the indicated logicalTypeFactory class.
> * At this point, the existing logic will treat the new custom type the same
> as "uuid" is treated and will generate SpecificRecord classes with fields of
> that type.
> I could implement this pretty trivially, if there's an appetite for it. This
> would seem to be 100% backwards compatible.
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