Archive for the ‘Scala’ Category
Gradle, Lift, and Google App Engine January 21, 2012 | 08:34 pm

I’m getting back into the game a little bit, and I decided to take a look at Lift for web development. After an initially promising experience, I became totally unhappy with Eclipse (it began forgetting I had Google App Engine libraries on the classpath after every clean). So I moved back to the command line. The recommendation to use Simple Build Tool or Maven for Lift put me off: SBT is pretty weak for a build tool, and Maven is…well…Maven, off to download the Internet. So I went back to Gradle.

For the record, I’m using Objectify for my Google App Engine development, because JPA gets you into that whole ugly ORM conceptual space without need: there’s no “R” in GAE, so you might as well deal with it in a more natural way.

So, given that situation, I came up with this build.gradle script. (Forgive the ugly organization, but this is actually the relevant points extracted from a multi-project build.)

buildscript {
   repositories {
      add(new org.apache.ivy.plugins.resolver.URLResolver()) {
          name = 'GitHub'
          addArtifactPattern '[organisation]/[module]/[module]-[revision].[ext]'
  dependencies {
    classpath "bmuschko:gradle-gae-plugin:$gaePluginVersion"
apply plugin:'java'
// Buildscript dependencies and repositories
repositories {
  mavenRepo name:'scala-releases', url:''
  mavenRepo name:'objectify-appengine-releases', url:''
  mavenRepo name:'sonatype-releases', url:''
  mavenRepo name:'sonatype-snapshots', url:''
  add(new org.apache.ivy.plugins.resolver.URLResolver()) {
      name = 'GitHub'
      addArtifactPattern '[organisation]/[module]/[module]-[revision].[ext]'
// Universal dependencies
dependencies {
  compile "org.encog:encog-core:$encogVersion",
  testCompile "junit:junit:4.5"
// Now the Scala stuff
apply plugin: 'scala'
dependencies {
  scalaTools "org.scala-lang:scala-compiler:$scalaVersion",
   compile "org.scala-lang:scala-library:$scalaVersion"
  testCompile "org.scala-tools.testing:specs:1.6.1",
apply plugin:'war'
dependencies {
  compile "net.liftweb:lift-webkit_$scalaVersion:$liftVersion",
  testCompile 'org.mortbay.jetty:jetty-util:6.1.22',
  providedCompile 'javax.servlet:servlet-api:2.5'
apply plugin: 'gae'
dependencies {
    compile "com.googlecode.objectify:objectify:$objectifyVersion"
    gaeSdk "$gaeVersion"
gae {
  downloadSdk = true
  disableUpdateCheck = true // Error with HTTPS
  appcfg {
    email = '[email protected]'
    logs {
      append = true
      severity = 1
      ouputFile = file('build/logs.txt')

I stash versions in the file, which looks like this (it’s a lot more details than you actually need):

scalaVersion = 2.9.1
liftVersion = 2.4-RC1
gaePluginVersion = 0.5.2
objectifyVersion = 4.0a2
guavaVersion = 11.0.1
commonsLang3Version = 3.1
commonsLangVersion = 2.6
commonsIoVersion = 2.1
commonsCollectionsVersion = 3.2.1
encogVersion = 3.1.0-SNAPSHOT
androidPluginVersion = 1.1.0
slf4jVersion = 1.6.4
gaeVersion = 1.6.1

If you start Lift up at this point (using gradle gaeRun), there are errors about Lift not having permission to mess with the thread pool.

Now, here’s the amazing magic trick which I found documented nowhere but discovered while digging through the Lift source code. It’s an astounding and miraculous trick which is necessary in order to get Lift to work on Google App Engine.

In the file ./src/main/resources/props/default.props, make sure to have this set:


That’s it. You do that, Google App Engine works. You don’t do that, it won’t. Magic!

Scala Scripting Challenge: What’s Equivalent to this Groovy? May 20, 2009 | 05:48 pm

Inspired by Scala being in the Scripting Language Bowl, I wanted to take a look at Scala as a scripting language.

I’ve got this little Groovy code snippet:

( =~ /b((p{Lu}p{Ll}+)+)b/).each {
  println "I found: ${it[0]}"

When run, it looks like this:

$ echo "
" | groovy ./CapitalInput.groovy 
I found: Foo
I found: Baz
I found: Fischer
I found: Weller

What’s a nice Scala equivalent? Here’s the best I could come up with:

val text = Source.fromInputStream("")
"""b((p{Lu}p{Ll}+)+)b""".r.findAllIn(text).foreach { found:String =>
    println("I found: " +  found)

That’s actually not too bad, but does anyone have anything better? Any obvious mistakes I’m making?