Tuesday, January 9, 2007

Scala Baby-Steps

I'm starting to learn Scala. It's a statically- and strongly-typed functional language that compiles to Java byte code and integrates well with Java.

One of the things I'm struggling with is the language's strong static typing. Scala is nice in that it tries very hard to infer types. That means the programmer doesn't spend much time typing "wasteful" type declarations. If Scala didn't have that, I would have run away screaming already.

I've figured out how to connect to a MySQL database. There are a few database access methods that are being developed in Scala. The one that ships with the language is called "dbc". It comes with a PostgreSQL connection interface but no MySQL version. Here's my MySQL version along with some simple code that performs a select. (I'd move the connection information into a properties file if I were to really use this code.)

import scala.dbc._
import scala.dbc.Syntax._
import scala.dbc.syntax.Statement._
import java.net.URI

object MysqlVendor extends Vendor {
  val uri = new URI("jdbc:mysql://localhost:3306/my_database_name")
  val user = "my_database_user"
  val pass = "my_database_password"
  
  val retainedConnections = 5
  val nativeDriverClass = Class.forName("com.mysql.jdbc.Driver")
  val urlProtocolString = "jdbc:mysql:"
}

object BulkUploadRunner extends Application {
  val db = new Database(MysqlVendor)

  val rows = db.executeStatement {
    select fields ("email_id" of characterVarying(32)) from ("bulk_uploads")
  }
  for (val r <- rows;
       val f <- r.fields) {
    Console.println(f.content.nativeValue) // or .sqlValue
  }

  db.close
}
Link

4 comments:

Anonymous said...
This comment has been removed by a blog administrator.
renghenthecow said...

how do we an insert???

I do not find any tutorial on that

Jim Menard said...

I don't know. I did some research for 1/2 hour and came up with some code that almost compiled, but not quite. It uses the Insert and InsertData classes.

I also looked at the liftweb code. It builds the SQL insert statment, then uses the database connection and a prepared statement.

Sorry I can't be of more help. Perhaps you should ask on the Scala mailing list.

Harshad said...

@renghen

check out http://hrj.wikidot.com/scaladbc