Scala/Lift Database Connections

Question

I am working on a new web application using Scala with Lift. I want to make it reusable so others might install it on their own servers for their own needs. I come out of a PHP background where it is common practice to create an install form asking for database connection details. This information is stored in a configuration file and used by the rest of the PHP application for connecting to the database. It is extremely convenient for the user because everything is contained within the directory storing the PHP files. They are free to define everything else. My Java/Scala background has all been enterprise work where an application was only intended to run on the database we setup for it. It was not meant to be installed on others' web servers or with different databases.

So my question is how is this typically done for the Java/Scala world? If there are open source applications implementing the mainstream solution, feel free to point me to those too.

thoredge thoredge · Accepted Answer · 2011-02-17T08:34:07

I use this to set up the database:

val vendor =
  new StandardDBVendor(
    Props.get("db.driver") openOr "org.h2.Driver",
    Props.get("db.url") openOr "jdbc:h2:mem:db;AUTO_SERVER=TRUE",
    Props.get("db.user"), 
    Props.get("db.password"))
LiftRules.unloadHooks.append(vendor.closeAllConnections_! _)
DB.defineConnectionManager(DefaultConnectionIdentifier, vendor)

The 'Props' referred to will then be (by default) in the file default.props in the props directory in resources.

Updated: This is what I do on servers in production. With 'Props.whereToLook' you provide a function that retrieves an input stream of the configuration. This can be a file as in the example below or you could for example fetch it over network socket.

You will probably let the application to fail with an error dialog.

val localFile = () => {
  val file = new File("/opt/jb/myapp/etc/myapp.props")
  if (file.exists) Full(new FileInputStream(file)) else Empty
}
Props.whereToLook = () => (("local", localFile) :: Nil)

Scala/Lift Database Connections

2 Answers