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https://issues.apache.org/jira/browse/AVRO-1582?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17761367#comment-17761367
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Michael Nielson commented on AVRO-1582:
---------------------------------------
The Jackson solution has a few major problems. A mixin to exclude
getSpecificData and getSchema helps quite a bit but then falls down as soon as
you don't provide json for fields with defaults, for instance in idl:
{code}
record Blah {
string id;
array<string> someBoringArray = [];
}
{code}
It would be nice to deserialize this from the json:
{code}
{ "id": "some-id" }
{code}
You can almost get the example below to work, Jackson will give you a Blah
instance, but as soon as you try and serialize that entity to Avro you will get
an exception stating that someBoringArray cannot be null.
{code}
Blah blah = new ObjectMapper().readValue(Blah.class, "{ \"id\": \"some-id\" }");
{code}
To solve for that I update my record.vm template to add the JsonDeserialize
annotation to my record classes:
{code}
@com.fasterxml.jackson.databind.annotation.JsonDeserialize(builder =
${this.mangleTypeIdentifier($schema.getName())}.Builder.class)
{code}
And then this annotation to my builders:
{code}
@com.fasterxml.jackson.databind.annotation.JsonPOJOBuilder(buildMethodName =
"build", withPrefix = "set")
{code}
Since I am mucking with the velocity template anyway I added
@java.beans.Transient to the getSchema and getSpecificData methods.
I am quite happy with this solution.
Would there be any interest in a PR with the change?
I don't see annotations as a part of the public API (but I'll search around for
a mixin style Jackson integration for builders, because that would be even
better).
> Json serialization of nullable fields and fields with default values
> improvement.
> ---------------------------------------------------------------------------------
>
> Key: AVRO-1582
> URL: https://issues.apache.org/jira/browse/AVRO-1582
> Project: Apache Avro
> Issue Type: Improvement
> Components: java
> Affects Versions: 1.8.0
> Reporter: Zoltan Farkas
> Priority: Major
> Attachments: AVRO-1582-PATCH
>
>
> Currently serializing a nullable field of type union like:
> "type" : ["null","some type"]
> when serialized as JSON results in:
> "field":{"some type":"value"}
> when it could be:
> "field":"value"
> Also fields that equal the the default value can be omitted from the
> serialized data. This is possible because the reader will have the writer's
> schema and can infer the field values. This reduces the size of the json
> messages.
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