Avro Decoder with support optional fields in JSON. Based on Celos fork.

Gradle

dependencies { implementation 'com.github.goodforgod:avro-json-optional-decoder:1.1.6' }

Maven

<dependency> <groupId>com.github.goodforgod</groupId> <artifactId>avro-json-optional-decoder</artifactId> <version>1.1.6</version> </dependency>

Library is Java 1.8 compatible.

Library is compatible with different Apache Avro versions. Please use compatible library version for your Apache Avro version.

For given AVRO Schema.

{ "type" : "record", "name" : "Person", "fields" : [ { "name" : "username", "type" : "string" }, { "name" : "name", "type" : [ "null", "string" ] } ] }

Such JSON will be treated correctly.

{"username":"user1","name":null}

However, such JSON (name field is missing).

{"username":"user1"}

Will fail with:

org.apache.avro.AvroTypeException: Expected field name not found: name 

JsonOptionalDecoder provided by library allow correct JSON validation in both cases, decoding JSON that doesn't specify optional values, provided they have defaults.

Check guides on how-to-use Avro Decoders.

Be aware JsonOptionalDecoder is not thread-safe.

For given AVRO Schema.

{ "name": "Test", "type": "record", "fields": [ { "name": "required", "type": "string" }, { "name": "inner", "type": [ "null", { "name": "inner", "type": "record", "fields": [ { "name": "req", "type": "string" } ] } ] } ] }

This input will be correct:

{"required":"u", "inner": {"req": "q"}}

As this input will be correct:

{"required":"u"}

If property default is not specified, then missing field will be treated as avro null value.

{ "name" : "name", "type" : [ "null", "string" ] }

You can specify default value as per AVRO specification.

Keep in mind you mind putting type corresponding to default value first, due to AVRO incorrect union type validation.

{ "name" : "name", "type" : [ "string", "null" ], "default": "bob" }

Change

Decoder decoder = DecoderFactory.get().jsonDecoder(SCHEMA, INPUT_STREAM_OR_STRING);

With

Decoder decoder = new JsonOptionalDecoder(SCHEMA, INPUT_STREAM_OR_STRING);

This project licensed under the MIT - see the LICENSE file for details.