Scala-Web-REPL

Scala-Web-REPL uses a web terminal as the interactive console. Especially, it can be used as a inspector for applications, or even as a hot code modification mechanism.

It uses a scala interpreter to execute codes internally. If NO connected clients, this internal interpreter will be closed after 60 seconds(configurable).

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The Http Server

After searching a small http server for several days, I planned to write one for Scala-Web-REPL, which is named s-server. You can see it on https://github.com/woshilaiceshide/s-server .

At the very beginning, s-server is intended for a dedicated server for this project, which helps saving resource and simplifing development. But now it's a general nio socket server and a general http server, and will evolve independently.

How to Build It?

build s-server, which provides 'HTTP', from https://github.com/woshilaiceshide/s-server . Maybe you can just 'publishLocal' for test.

build Scala-Web-REPL

• git clone https://github.com/woshilaiceshide/scala-web-repl.git
• cd ./scala-web-repl
• sbt package

How to Use It?

After started, browse http://${host}:${port}/asset/wrepl.html

Code Example

package woshilaiceshide.wrepl

case class Cat(color: String, age: Int) {
  def mewl = s"mewling at ${System.currentTimeMillis()}"
}

object DefaultBootstrap extends App {

  val whiteCat = Cat("white", 3)
  val blackCat = Cat("black", 10)

  def who_is_older(a: Cat, b: Cat) = {
    if (a.age > b.age) Some(a)
    else if (a.age < b.age) Some(b)
    else None
  }

  import scala.tools.nsc.interpreter.NamedParam
  import scala.tools.nsc.interpreter.NamedParamClass

  //val config = com.typesafe.config.ConfigFactory.parseFileAnySyntax(new java.io.File("conf/application.conf"))
  val config = com.typesafe.config.ConfigFactory.load()
  val max_lines_kept_in_output_cache = config.getInt("max_lines_kept_in_output_cache")
  val repl_max_idle_time_in_seconds = config.getInt("repl_max_idle_time_in_seconds")

  val server = new Server(
    "0.0.0.0",
    8181,
    Seq(NamedParam("whiteCat", whiteCat),
      NamedParam("blackCat", blackCat),
      NamedParamClass("who_is_older", "(woshilaiceshide.wrepl.Cat, woshilaiceshide.wrepl.Cat) => Option[woshilaiceshide.wrepl.Cat]", who_is_older _)),
    max_lines_kept_in_output_cache = max_lines_kept_in_output_cache,
    repl_max_idle_time_in_seconds = repl_max_idle_time_in_seconds)

  server.start()
}

TODO

• I'll write some utilities to help introspection for applications based on akka, spray and play. Any interested guy is appreciated.

• How to authenticate clients?

• How to forbid 'System.exit(-1)', or do more sophisticated restrictions?

• Will some jvm options make Scala-Web-REPL sad?

Enjoy It

Any feedback is expected.