Scalamo - Scala API for DynamoDB

The Java API for DynamoDB is verbose and cumbersome, and while it's fully usable from Scala, there is a need for a cleaner and more elegant way to interact with DynamoDB when one is working in Scala.

This library is in its early stages, with an initial focus on automatic typesafe mapping between Scala case classes and DynamoDB Item objects. It uses Shapeless to achieve this rather than runtime reflection, so the compiler will catch any case classes that are not mappable.

Due to the unstructured nature of DynamoDB rows, any particular mapping could potentially fail at runtime, so the Validated class from Cats is used to provide a result that is either a Valid instance of the requested case class or an Invalid result with all errors collected in a NonEmptyList.

All the standard types supported by the Item class are supported in Scalamo. Mappers for Java 8 ZonedDateTime and Instant values are also provided. ZonedDateTime values are stored as strings in ISO-8601 format and Instant values are stored as Longs.

Example

import cats.data.Validated.{Invalid, Valid}
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder
import com.amazonaws.services.dynamodbv2.document.DynamoDB
import java.time.Instant
import scalamo.{Table, Validated}

case class User(userId: String, name: String, lastLogin: Instant)

object Example extends App {
  val dynamoDB = new DynamoDB(AmazonDynamoDBClientBuilder.defaultClient())
  val table = Table[User](dynamoDB, "users")

  val users = Seq(
    User("mark-o", "Mark Corrigan", Instant.now()),
    User("jez", "Jeremy Usborne", Instant.now()),
    User("superhans", "Super Hans", Instant.now())
  )

  // batch write users
  table.put(users)

  // retrieve one user
  val maybeUser: Option[Validated[User]] = table.get("userId", "mark-o")
  maybeUser match {
    case Some(Valid(user)) =>
      table.put(user.copy(lastLogin = Instant.now()))
      println("Updated user")
    case Some(Invalid(errors)) =>
      println(s"Errors parsing user item: $errors")
    case None =>
      println("Not found")
  }

  // batch get users
  val maybeUsers: Validated[Seq[User]] = table.get("userId", Seq("jez", "superhans", "sophie"))
  for {
    users <- maybeUsers
    user <- users
  } println(user)
}

Note that scalamo.Validated is defined as:

type Validated[A] = cats.data.ValidatedNel[Throwable, A]

jlandahl/scalamo

Scalamo - Scala API for DynamoDB

Example