Details
Blocker Description
As part of AVRO-753, we modified the Encoder API to be more like the current Decoder API. This issue tracks related changes to solidify the API of both Encoder and Decoder to be more stable and consistent. It is expected that the result will be long-lived and not require major changes in the future for the following reasons:
- Instantiation and configuration will be funneled through EncoderFactory and DecoderFactory. Individual implementation types and constructors are not exposed. With this abstraction we could, for example, put the features of BlockingBinaryEncoder into BufferedBinaryEncoder and not break any user code. We already have some of this distinction on the Decoder side, but not all BinaryDecoders are going through the factory.
- The core Encoder and Decoder abstract classes will not declare configuration methods or constructors. This makes them 'pure' low level Avro read/write API constructs. This separation of concerns means, for example, that not all encoder implementations need wrap an OutputStream because of init(OutputStream out).
- The core Encoder and Decoder API does not know or care about Schemas, resolution, or any other 'higher order' Avro concept. This is the pure separation of concern for writing/reading primitive Avro types to/from somewhere.
- Implementations have been heavily performance tuned on both sides, so changes to the API necessary for high performance will not be likely.
The Factories will adhere to the following general principles:
- configuration options that do not affect the semantics of a type can be set through the factory. i.e. buffer sizes.
- configuration that affects the semantics or changes the output or supported input will have separate factory methods. For example, choosing between an implementation that requires calling flush() and one that does not, requires choosing a different factory method to instantiate. This is important because it generally means that client code explicitly requests the behavioral type, and that helps prevent bugs caused by accidentally configuring a factory to return an object that is incompatible with the use case.