at Scala Conference in Japan 2013

1. Scala Frustrations
in Real Development
Naoki Takezoe
@takezoen
NTT-DATA INTELLILINK

2. Abstract
• Scala is pretty good for real development.
• However Scala has also some bad points.
• Please note for these points when you introduce
Scala into real development.

3. Scala 300 Recipes from Shoeisha
• Includes 300 Practical Scala
Recipes.
• from Basic Scala topics to
frameworks and tools.
Covers Play2, Akka, sbt, scaladoc, ScalaIDE,
ScalaTest, Specs2, Scalatra, ScalaQuery,
Anorm, Casbah, spray, scala-io, scala-time,
sjson, util-eval, scalaxb, Dispatch and more.

4. Why we are using Scala?
• Decrease costs of system development.
• We felt the limit of Java several years ago.
• Scala might be a breakthrough?

5. About Our Project
• Porting Java based web application to Scala.
• Over 170 HTMLs and 40,000 lines.
• 5 members on 6 months.
Before After
 Seasar2  Play2 (Customized)
 Apache Click  ScalaQuery (Cuztomized)
 S2JDBC  PostgreSQL
 PostgreSQL + Tsearch  Apache Solr
 Raw JavaScript  jQuery + jQuery UI

6. Benefits of Scala
• Decrease amount of source code
▫ 40%-50% OFF
▫ Better abstraction techniques
• Decrease bugs
▫ More type safe
▫ Immutable data types
• Java Interoperability
▫ Many Java based Frameworks and Libraries are
available
▫ Easy to port existing Java software

7. Benefits of Scala
• Decrease amount of source code
▫ 40%-50% OFF
▫ Better abstraction techniques
Flexibility and Safety
• Decrease bugs
▫ More type safe
▫ Immutable data types
• Java Interoperability
▫ Many Java based Frameworks and Libraries are
available
▫ Easy to port existing Java software

9. Long compilation time
• Compilation is so much heavy.
• Painful for large application development.

10. Solution
Buy high spec machines
Asynchronous and automated build

11. ScalaIDE is heavy
• We meet a sandglass frequently.

12. Solution
1. Turn off the incremental builder
2. Turn off the code completion
3. Try other IDE or text editor

13. sbt is NOT Simple Build Tool
• When we get a trouble, difficult to find a reason.
• Rapid version up causes compatibility problem
of sbt plugins.

14. Solution
We really need SBT in Action!

16. Long compilation time
• Many code generation and template compilation.
• Development mode is slow also.

17. Solution
Buy high spec machines
Divide large project
play2-fastassets decreases request

18. Inflexible Validation
• Client-side validation is not provided.
• Error Message can’t be contained field name.

19. Solution
Original client-side validation framework
based on Play2’s form definition
Original helper to display error messages

20. Anorm is too simple
• We have to write all SQL.
• Magic does not already exist.
• SQL is not type safe.
• No support for dynamic SQL.

21. Solution
Use other ORMs such as ScalaQuery.
We used a combination of scalaquery-magic
scalagen and mirage-scala.

22. Function22 Problem in form definition
• a.k.a. Tuple22 Problem
• Form can not have over 18 properties.
val userForm = Form(
mapping(
"firstName“ -> text,
"lastName“ -> text,
"mailAddress“ -> email,
"password“ -> text,
... Max 18 properties
"tel“ -> text,
"mobile“ -> text,
"company“ -> text,
"department“ -> text
)(UserInfo.apply)(UserInfo.unapply)
)

23. Solution
Nested definition, BUT it’s not expectable.
val userForm = Form(
mapping(
"firstName" -> text,
"lastName" -> text,
"mailAddress" -> email,
"password" -> text,
"companyInfo" -> mapping(
"company" -> text,
"department" -> text
)(CompanyInfo.apply)(CompanyInfo.unapply)
)(UserInfo.apply)(UserInfo.unapply)
)

24. No Servlet and HttpSession
• Hard to port existing Java based web apps.
• We want to run Play2 on the servlet container by
un-technical reasons.

25. Solution
play2-war-plugin packs Play2 apps to war.
play2-httpsession provides HttpSession
by using with play2-war-plugin.

27. solr-scala-client
https://github.com/takezoe/solr-scala-client
• Simple wrapper of SolrJ for Scala.
• Query converter using parser combinator.
import jp.sf.amateras.solr.scala._
val client = new SolrClient("http://localhost:8983/solr")
val result = client.query("name: ?name?")
.getResultAsMap(Map("name" -> "ThinkPad & X201s"))
// => name:("ThinkPad" AND "X201s")
result.documents.foreach { doc: Map[String, Any] =>
...
}

28. scalagen
https://github.com/takezoe/scalagen
• Code Generator from RDBMS.
• Supports Anorm and ScalaQuery in the current version.
• Easy to add support for other ORMs.
• Work as CLI and sbt plugin.
seq(jp.sf.amateras.scalagen.ScalagenPlugin.scalagenSettings: _*)
scalagenConfiguration := jp.sf.amateras.scalagen.Settings(
// for ScalaQuery
generator = new jp.sf.amateras.scalagen.ScalaQueryGenerator(),
// for Anorm
//generator = new jp.sf.amateras.scalagen.ScalaQueryGenerator(),
driver = "org.hsqldb.jdbcDriver",
url = "jdbc:hsqldb:hsql://localhost/",
username = "sa",
password = ""
)

29. scalaquery-magic
https://github.com/shimamoto/scalaquery-magic
• Extends ScalaQuery.
• Make a Magic (like old Anorm’s Magic) by code
generation using scalagen.
val userInfoDao = new UserInfoDao()
// SELECT by ID
val userInfo = userInfoDao.selectById(1)
// INSERT
userInfoDao.insert(UserInfo(DEFAULT[Int], 'userName', 'password'))
// UPDATE
userInfoDao.update(userInfo.copy(userName = 'newName'))
// DELETE by ID
userInfoDao.deleteById(1)

30. mirage-scala
https://github.com/takezoe/mirage-scala
• SQL Centric ORM similar to Anorm.
• Executable SQL template called 2waySQL.
SLEECT USER_ID, USER_NAME, PASSWORD
FROM USER_INFO
/*BEGIN*/
WHERE
/*IF userId != null*/
USER_ID = /*userId*/1
/*END*/
/*IF userId != null*/
USER_NAME = /*userName*/ 'takezoe'
/*END*/
/*END*/

31. play2-httpsession
https://github.com/takezoe/play2-httpsession
• Provide HttpSession for Play2 applications.
• Work with play2-war-plugin.
import jp.sf.amateras.play2.httpsession.HttpSessionSupport._
def index = Action { implicit request =>
// retrieve the object from HttpSession
val value: Option[String] = HttpSession[String]("key")
Ok(value).withHttpSession {
// store objects into HttpSession
"key" -> "value"
}
}

32. play2-fastassets
https://github.com/takezoe/play2-fastassets
• Decrease amount of request to external CSS,
JavaScript and images by browser cache.
@(title: String)(content: Html)
@import jp.sf.amateras.play2.fastassets.FastAssets
<!DOCTYPE html>
<html>
<head>
<title>@title</title>
<link rel="stylesheet" media="screen" href="@FastAssets.at("stylesheets/main.css")">
<link rel="shortcut icon" type="image/png" href="@FastAssets.at("images/favicon.png")">
<script src="@FastAssets.at("javascripts/jquery-1.7.1.min.js")" type="text/javascript"></script>
</head>
<body>
@content
</body>
</html>

34. Scala is practical
• You are evangelists of Scala.
• Please introduce Scala in your work.
• But so carefully, especially in the large project.

35. Scala is now glowing up!
• This way along which Java passed.
• Time will solve these problems.
• We can contribute Scala glowing.