avro4s

Avro4s is a scheme/class generation and serializing/deserializing library for Avro written in Scala. The objective is to allow seamless use with Scala without the need to to write boilerplate conversions yourself, and without the runtime overhead of reflection. Hence, this is a macro based library and generates code for use with avro at compile time.

The features of the library are:

Schema generation from classes at compile time
Class generation from schemas at build time
Boilerplate free serialization of classes to avro
Boilerplate free deserialization of avro to classes

Changelog

0.94.0 - Added support for writing/reading Either and Option in serializer/deserializer. Fixed bug with array serialization.
0.93.0 - Added support for either and options in schema generator. Added support for aliases via scala annotation.
0.92.0 - Added support for unions (and unions of nulls to Options) and enums to class generator.

Serializing

Avro4s allows us to easily serialize Scala case classes into an avro stream.

Lets first create some instances to serializer:

case class Artist(name: String, yearOfBirth: Int, yearOfDeath: Int, birthplace: String, methods: Seq[String])
val michelangelo = Artist("michelangelo", 1475, 1564, "Caprese", Seq("sculpture", "fresco"))
val raphael = Artist("raphael", 1483, 1520, "Florence", Seq("painter", "architect"))

Then we can create an AvroOutputStream which we write to, and close, just like you would any regular output stream. Note that when we create the output stream we must specify the type it will accept. We first include the import AvroImplicits._ line as the macros that generate the writers and schemas are located there.

import AvroImplicits._ // contains the macros that do the magic
import java.nio.file.Paths
import com.sksamuel.avro4s.AvroOutputStream 

val path = Paths.get("artists.avro")
val out = AvroOutputStream[Artist](path)
out.write(painters)
out.close()

Deserializing

With avro4s we can easily deserialize a file back into Scala case classes. Given the artists.avro file we generated in the previous section on serialization, we will read this back in using the AvroInputStream class. We first include the import AvroImplicits._ line as the macros that generate the readers and schemas are located there.

import AvroImplicits._ // contains the macros that do the magic

val path = Paths.get("artists.avro")
val in = AvroInputStream[Artist](path)
val painters = in.iterator.toSet
println(painters) // 
in.close()

Schemas

To generate a schema for a given case class, we need to import a schema implicit and that's all.

implicit val s = AvroImplicits.schemaFor[Artist]
println(s.schema)

would output

{  
   "type":"record",
   "name":"Artist",
   "namespace":"com.sksamuel.avro4s",
   "fields":[  
      {  
         "name":"name",
         "type":"string"
      },
      {  
         "name":"yearOfBirth",
         "type":"int"
      },
      {  
         "name":"yearOfDeath",
         "type":"int"
      },
      {  
         "name":"birthplace",
         "type":"string"
      },
      {  
         "name":"styles",
         "type":{  
            "type":"array",
            "items":"string"
         }
      }
   ]
}

Type Mappings

Scala Type	Avro Type
Boolean	boolean
Array[Byte]	bytes
String	string or fixed
Int	int
Long	long
BigDecimal	decimal
Double	double
Float	float
sealed trait T	enum
scala.collection.Array[T]	array
scala.collection.List[T]	array
scala.collection.Seq[T]	array
scala.collection.Iterable[T]	array
scala.collection.Set[T]	array
scala.collection.Map[String, T]	map
scala.collection.Option[T]	union:null,T
scala.collection.Either[L, R]	union:L,R
T	record

Todo

Features to be added before 1.0 release

Annotation for Avro properties
Annotation for aliases
Error handling during deserialization

Using avro4s in your project

Gradle: compile 'com.sksamuel.avro4s:avro4s-core_2.11:0.93.0'

SBT: libraryDependencies += "com.sksamuel.avro4s" %% "avro4s-core" % "0.93.0"

Maven:

<dependency>
    <groupId>com.sksamuel.avro4s</groupId>
    <artifactId>avro4s-core_2.11</artifactId>
    <version>0.93.0</version>
</dependency>

The above is just an example and is not always up to date. Check the latest released version on maven central

Building and Testing

This project is built with SBT. So to build

sbt compile

And to test

sbt test

Contributions

Contributions to avro4s are always welcome. Good ways to contribute include:

Raising bugs and feature requests
Fixing bugs and enhancing the DSL
Improving the performance of avro4s
Adding to the documentation

License

The MIT License (MIT)

Copyright (c) 2015 Stephen Samuel

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

garyfrost/avro4s