JarCasting
web3scala
web3scala allows seamless integration with Ethereum blockchain, using Scala programming language.
Lightweight, efficient, using Scala idioms, it spares you the trouble of writing own low-level code controlling the work of Ethereum nodes.
Features
- Complete implementation of JSON-RPC Ethereum client API over HTTP
- Support for Whisper v5 (work in-progress)
Getting started
SBT
libraryDependencies += "org.web3scala" % "core" % "0.1.0"
Ethereum client
$ geth --rpcapi personal,db,eth,net,web3,shh --shh --rpc --testnet
Sending requests
val service = new Service
// synchronous call (returns Either[Error, Response])
service.web3ClientVersion match {
case Left(e) => println("Error: " + e.error)
case Right(s) => println("Client Version: " + s.result)
}
// asynchronous call (returns a future wrapped in AsyncResponse)
val future = service.asyncWeb3ClientVersion.future
val response = future().as[GenericResponse]
response.result match {
case Some(s) => println(s)
case None => println(response.error)
}
Stacking futures
Assuming you have three Ethereum wallets:
val rq1 = ("0x1f2e3994505ea24642d94d00a4bcf0159ed1a617", BlockName("latest"))
val rq2 = ("0xf9C510e90bCb47cc49549e57b80814aE3A8bb683", BlockName("pending"))
val rq3 = ("0x902c4fD71e196E86e7C82126Ff88ADa63a590d22", BlockNumber(1559297))
and want to choose one with most Ether in it:
val result = highestBalance(rq1, rq2, rq3)
println("Highest Balance: " + result())
Here's how to achieve that with web3scala:
def highestBalance(requestParams: (String, Block)*) = {
// execute async requests
val responses =
for (requestParam <- requestParams)
yield requestParam._1 -> service.asyncEthGetBalance(requestParam._1, requestParam._2)
// parse responses
val futures =
for (response <- responses)
yield for (json <- response._2.future)
yield response._1 -> Utils.hex2long((json \ "result").extract[String])
// select max balance and return corresponding address
for (future <- Future.sequence(futures))
yield future.maxBy(_._2)._1
}
Result:
$ Highest Balance: 0x1f2e3994505ea24642d94d00a4bcf0159ed1a617
The code is non-blocking on I/O at any point, and http requests execution fully parallelized. You'll find a working sample in the examples directory.
Dependencies
The library has following runtime dependencies:
- Dispatch Reboot for asynchronous HTTP interaction
- Json4s-Jackson for JSON parsing/generation
- jackson-module-scala to support Scala-specific datatypes
