Wrapper catching exceptions accured on db.run call - scala

Question

In our project we always injecting dbConfigProvider: DatabaseConfigProvider in our bean objects and then doing database operations with db.run(some query), it returns Future. How can I write a logging wrapper for db.run which will print all sql exceptions.
Example:
class SomeBeanImpl #Inject()(dbConfigProvider: DatabaseConfigProvider) {
private val logger = Logger(getClass)
def someDBQuery() = {
db.run(some wrong sql query) // exception raised in future, I need to print it with logger
}
}
Note:
If I add .onFailure on each db.run call it will mess up my code very badly. That's why I need write this wrapper for all of db.run calls.
If I wrap db.run in some function with different signature, I must change it in many places, which is not the best option. How can I do it implicitly?

Answer 1

You don't need to explicitly create a new wrapper class, you can use the Pimp My Library pattern to create an implicit method which wraps the invocation of db.run and attaches a onFailure to the Future:
object MyExtensions {
class DbExtensions(db: Db) {
def runAndLog(query: String): Future[String] = {
val result = db.run(query)
result.onFailure {
case e => Logger.getLogger("x").error(s"Exception: $e")
}
result
}
}
implicit def dbExtention(db: Db): DbExtensions = new DbExtensions(db)
}
class Db {
def run(query: String): Future[String] = Future.successful("Hello")
}
object App extends Application {
import MyExtensions._
val db = new Db
db.runAndLog("hello")
}
For Scala 2.10 and above, this can be shortened significantly using Implicit Classes:
implicit class DbExtensions(val db: Db) {
def runAndLog(query: String): Future[String] = {
val result = db.run(query)
result.onFailure {
case e => Logger.getLogger("x").error(s"Exception: $e")
}
result
}
}
class Db {
def run(query: String): Future[String] = Future.successful("Hello")
}
object App extends Application {
val db = new Db
db.runAndLog("hello")
}
You can further make DbExtensions extend AnyVal for a performance optimization:
implicit class DbExtensions(val db: Db) extends AnyVal

Answer 2

Make a new class:
case class DBWrapper(db: DatabaseComponent) {
def run(query: String) = db.run(query).onFailure { case e => logger.error(e) }
}
And replace your db wherever you initialize it with DBWrapper(db).
You can make the conversions back and forth implicit too, although I would not recommend it in this case.