Slick: factory method SlickSession.forDbAndProfile

docs/src/main/paradox/slick.md

@@ -84,6 +84,13 @@ SQL Server
 
 Of course these are just examples. Please visit the @extref[Slick documentation for `DatabaseConfig.fromConfig`](slick:api/index.html#slick.jdbc.JdbcBackend$DatabaseFactoryDef@forConfig(String,Config,Driver,ClassLoader%29:Database) for the full list of things to configure.
 
+You also have the option to create a SlickSession from Slick Database and Profile objects.
+
+Scala
+:  @@snip [snip](/slick/src/test/scala/docs/scaladsl/SlickSpec.scala) { #init-session-from-db-and-profile }
+
+This can be useful if you need to share you configurations with code using Slick directly, or in cases where you first get the database information at runtime, as the Slicks Database class offer factory methods for that. This method is only available in the scaladsl, as Slick has no Java API and as such no easy way of creating a Database instance from Java.
+
 ## Closing a Database Session
 
 Slick requires you to eventually close your database session to free up connection pool resources. You would usually do this when terminating the `ActorSystem`, by registering a termination handler like this:

slick/src/main/mima-filters/1.1.x.backwards.excludes

@@ -0,0 +1,3 @@
+# New classes introduced for adding an extra factory method for SlickSession in #1509
+ProblemFilters.exclude[MissingClassProblem]("akka.stream.alpakka.slick.javadsl.SlickSession$SlickSessionImpl")
+ProblemFilters.exclude[DirectMissingMethodProblem]("akka.stream.alpakka.slick.scaladsl.package.SlickSession")

slick/src/main/scala/akka/stream/alpakka/slick/javadsl/package.scala

@@ -8,7 +8,6 @@ import slick.basic.DatabaseConfig
 import slick.jdbc.JdbcBackend
 import slick.jdbc.JdbcProfile
 import slick.jdbc.PositionedResult
-
 import com.typesafe.config.Config
 import com.typesafe.config.ConfigFactory
 
@@ -28,27 +27,32 @@ sealed abstract class SlickSession {
   def close(): Unit = db.close()
 }
 
-/**
- * Java API: Methods for "opening" Slick databases for use.
- *
- * <b>NOTE</b>: databases created through these methods will need to be
- * closed after creation to avoid leaking database resources like active
- * connection pools, etc.
- */
-object SlickSession {
-  private final class SlickSessionImpl(val slick: DatabaseConfig[JdbcProfile]) extends SlickSession {
+private[slick] abstract class SlickSessionFactory {
+  protected final class SlickSessionConfigBackedImpl(val slick: DatabaseConfig[JdbcProfile]) extends SlickSession {
     val db: JdbcBackend#Database = slick.db
     val profile: JdbcProfile = slick.profile
   }
+  protected final class SlickSessionDbAndProfileBackedImpl(val db: JdbcBackend#Database, val profile: JdbcProfile)
+      extends SlickSession
 
   def forConfig(path: String): SlickSession = forConfig(path, ConfigFactory.load())
   def forConfig(config: Config): SlickSession = forConfig("", config)
   def forConfig(path: String, config: Config): SlickSession = forConfig(
     DatabaseConfig.forConfig[JdbcProfile](path, config)
   )
-  def forConfig(databaseConfig: DatabaseConfig[JdbcProfile]): SlickSession = new SlickSessionImpl(databaseConfig)
+  def forConfig(databaseConfig: DatabaseConfig[JdbcProfile]): SlickSession =
+    new SlickSessionConfigBackedImpl(databaseConfig)
 }
 
+/**
+ * Java API: Methods for "opening" Slick databases for use.
+ *
+ * <b>NOTE</b>: databases created through these methods will need to be
+ * closed after creation to avoid leaking database resources like active
+ * connection pools, etc.
+ */
+object SlickSession extends SlickSessionFactory
+
 /**
  * Java API: A class representing a slick resultset row, which is used
  *          in SlickSource to map result set rows back to Java objects.

slick/src/main/scala/akka/stream/alpakka/slick/scaladsl/package.scala

@@ -4,6 +4,8 @@
 
 package akka.stream.alpakka.slick
 
+import slick.jdbc.{JdbcBackend, JdbcProfile}
+
 package object scaladsl {
 
   /**
@@ -21,5 +23,8 @@ package object scaladsl {
    * closed after creation to avoid leaking database resources like active
    * connection pools, etc.
    */
-  val SlickSession = javadsl.SlickSession
+  object SlickSession extends javadsl.SlickSessionFactory {
+    def forDbAndProfile(db: JdbcBackend#Database, profile: JdbcProfile): SlickSession =
+      new SlickSessionDbAndProfileBackedImpl(db, profile)
+  }
 }

slick/src/test/scala/docs/scaladsl/SlickSpec.scala

@@ -30,7 +30,7 @@ class SlickSpec extends WordSpec with ScalaFutures with BeforeAndAfterEach with
   //#init-mat
 
   //#init-session
-  implicit val session = SlickSession.forConfig("slick-h2")
+  implicit val session: SlickSession = SlickSession.forConfig("slick-h2")
   //#init-session
 
   import session.profile.api._
@@ -77,6 +77,26 @@ class SlickSpec extends WordSpec with ScalaFutures with BeforeAndAfterEach with
     TestKit.shutdownActorSystem(system)
   }
 
+  "SlickSession.forDbAndProfile" must {
+    "create a slick session able to talk to the db" in {
+      //#init-session-from-db-and-profile
+      val db = Database.forConfig("slick-h2.db")
+      val profile = slick.jdbc.H2Profile
+      val slickSessionCreatedForDbAndProfile: SlickSession = SlickSession.forDbAndProfile(db, profile)
+      //#init-session-from-db-and-profile
+      try {
+        val q = sql"select true".as[Boolean]
+        val result = Slick
+          .source(q)(slickSessionCreatedForDbAndProfile)
+          .runWith(Sink.head)
+          .futureValue
+        assert(result === true)
+      } finally {
+        slickSessionCreatedForDbAndProfile.close()
+      }
+    }
+  }
+
   "Slick.source(...)" must {
     def tupleToUser(columns: (Int, String)): User = User(columns._1, columns._2)