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An SBT plugin for automatically calling Avro code generation and a thin scala wrapper for reading and writing Avro files

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# Scavro

Scavro is an [SBT](http://www.scala-sbt.org/) plugin for automatically calling
Avro code generation and a thin scala wrapper for reading and writing
[Avro](http://avro.apache.org/) files.

The two components can work fully independently, so one can use the SBT plugin
to automate Avro's Java code generation and use the default
`SpecificDatumWriter` API supplied by Avro.

## Scavro Plugin

The Scavro Plugin is an SBT plugin that automates calling Avro's code
generation.  To use, you must import the scavro library into your project's SBT
settings by adding the following line to your `plugins.sbt` file:

```scala
addSbtPlugin("org.oedura" % "scavro-plugin" % "1.0.3")
```

Note that, whatever version of Scala you use in your
project, SBT runs on 2.10.

Avro schema and protocol files can then be added to
your `Build.scala` or `build.sbt` file.

```scala
avroSchemaFiles := Seq(file("SchemaFile.avsc"))
avroProtocolFiles := Seq(file("ProtocolFile.avpr"))
avroIDLFiles := Seq(file("AvroIdlFile.avdl"))
```

Running `sbt compile` will then call the avro-tools compiler and generate java
files into the directory specified by the `avroCodeOutputDirectory` SBT key.

Typically, although by no means necessarily, one would write a scala case class
wrapper around the java class(es) generated in order to use the scala reader and
writer described below.

A complete demonstration project is available as a reference.

# cd demo
    # sbt run
    [info] Running org.oedura.scavrodemo.ReadWriteDemo
    {"name": "Plywood table top", "price": 13.95, "quantity": 1}
    {"name": "2x4 raw lumber", "price": 2.95, "quantity": 2}
    {"name": "Wood Screws -- 3in No. 10", "price": 0.065, "quantity": 30}
    {"name": "Wood varnish (can)", "price": 3.95, "quantity": 1}
    -------------------------
    The order total comes to $25.75
    [success] Total time: 1 s, completed Sep 2, 2015 12:32:41 PM

## Scavro Reader and Writer

Scavro also provides a lightweight scala wrapper for Avro's read and write
functionality through the `AvroReader` and `AvroWriter` classes.  They can be
used to serialize or deserialize a `Seq` of objects that implements the
`AvroSerializeable` trait.  Additionally, there must be an implicit instance of
`AvroMetadata` to map the scala class to the code generated java class.  This
requirement can be met by using `LineItem` from the demo project as a
boilerplate template.

```scala
case class LineItem(name: String, price: Double, quantity: Int)
    extends AvroSerializeable {
  // Additional boilerplate omited
}

object LineItem {
  implicit def reader = new AvroReader[LineItem] { override type J = ... }
  implicit val metadata: AvroMetadata[LineItem, JLineItem] =
    new AvroMetadata[LineItem, JLineItem] { ... }
  }
}

dataToWrite: Seq[LineItem] = ...

// Write an avro file
val writer = AvroWriter[LineItem](filename)
writer.write(dataToWrite)

// Read an avro file
val reader: AvroReader[LineItem] = AvroReader[LineItem]
val dataRead: Seq[LineItem] = reader.read(filename)
```

To utilize the Scavro runtime classes add the following to your `build.sbt` or
`Build.scala` file.  This dependency is independent of the `addSbtPlugin`
command described in the _Scavro Plugin_ section.  Use that if you want the
compile time code generation functionality, use this if you want the runtime
functionality, and use both if you want both.

```scala
libraryDependencies ++= Seq(
  "org.oedura" %% "scavro" % "1.0.3"
)
```

The manual url specification is required because the runtime library and SBT
plugin are distributed in a single package.  This may change in version 1.0.

## Contributing

Contributions are welcome.  Submit pull requests to the master branch for core
improvements and bug fixes.  If you feel more ambitious, check out the
`code_generation` feature branch.

The demo project is considered an integration test and must run correctly before
pull requests will be accepted.  Run `stb test` in both the project root
directory *and also in the demo directory*.

## Authors

* Brian London <https://twitter.com/brianmlondon>

Thanks for assistance:

* Thierry Bertin-Mahieux <https://github.com/tbertinmahieux>
* Dhiren Bhatia <https://twitter.com/dhirenb>
* Mengxi Lu <https://twitter.com/mengxilu>

*... and the Oyster engineering team.*

## License

Licensed under the Apache 2.0 license.
http://www.apache.org/licenses/LICENSE-2.0

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