Question

我是scala / play / slick newbie所以如果我提出愚蠢的问题，请不要生气。

这就是问题。
我有几个光滑的表定义，这里有一个：

import javax.inject.Inject

import play.api.db.slick.{DatabaseConfigProvider, HasDatabaseConfigProvider}
import play.api.libs.concurrent.Execution.Implicits.defaultContext
import play.db.NamedDatabase
import slick.driver.JdbcProfile

import scala.concurrent.Future

case class User(id: Int, login: String, password: String) extends Identifiable

class UserDAO @Inject()(@NamedDatabase protected val dbConfigProvider: DatabaseConfigProvider) extends HasDatabaseConfigProvider[JdbcProfile] {
  import driver.api._

  private val users = TableQuery[UsersTable]

  def all(): Future[Seq[User]] = db.run(users.result)
  def insert(dog: User): Future[Unit] = db.run(users += dog).map { _ => () }
  def delete(id: Int): Future[Int] = db.run(users.filter(_.id === id).delete)


  private class UsersTable(tag: Tag) extends Table[User](tag, "USER") {
    def id = column[Int]("id", O.PrimaryKey, O.AutoInc)
    def email = column[String]("email")
    def password = column[String]("password")
    def * = (id, email, password) <> (User.tupled, User.unapply)
  }
}

想象一下，我有更多的表格有def id = column[Int]("id", O.PrimaryKey, O.AutoInc)来消除这个我需要写的东西：

trait Identifiable {
  this: Table[_] =>
  def id = column[String]("id", O.PrimaryKey)
}

但是如何以数据库无关的方式导入Table？此外，还有更多增强空间：提供对可识别表的访问的所有DAO对象都可以从包含all，insert，find和delete方法的公共抽象类继承。像（无法编译）的东西：

abstract class BaseDAO[E <: Identifiable] extends DAO[E] with HasDatabaseConfigProvider[JdbcProfile] {
  import driver.api._
  private val entities = TableQuery[BaseTable]

  def all(): Future[Seq[E]] = db.run(entities.result)
  def insert(entity: E): Future[Unit] = db.run(entities += entity).map { _ => () }
  def delete(entity: E): Future[Int] = db.run(entities.filter(_.id === entity.id).delete)
  def find(id: Int): Future[E] = db.run(entities.filter(_.id === entities.id))

  trait BaseTable { this: Table[_] =>
    def id = column[String]("id", O.PrimaryKey, O.AutoInc)
  }
}

有人可以指出我的错误吗？感谢。

Answer 1

数据库无关且代码具有高度可重用性

我正在使用Slick和Playframework，这就是我实现数据库不可知和通用存储库的方式。

请注意，此作品的灵感来自Active Slick

我希望在我的case class上定义这样的基本crud操作。我应该可以count，update，delete和create。我想只编写一次curd代码并永远重复使用它。

以下是演示此内容的片段。

case class Dog(name: String, id: Option[Long] = None)
Dog("some_dog").save()
Dog("some_dog").insert()
Dog("some_dog", Some(1)).delete()

CrudActions.scala

import slick.backend.DatabaseConfig
import slick.driver.JdbcProfile

import scala.concurrent.ExecutionContext


trait CrudActions {
  val dbConfig: DatabaseConfig[JdbcProfile]
  import dbConfig.driver.api._

  type Model

  def count: DBIO[Int]

  def save(model: Model)(implicit ec: ExecutionContext): DBIO[Model]

  def update(model: Model)(implicit ec: ExecutionContext): DBIO[Model]

  def delete(model: Model)(implicit ec: ExecutionContext): DBIO[Int]

  def fetchAll(fetchSize: Int = 100)(implicit ec: ExecutionContext): StreamingDBIO[Seq[Model], Model]
}

现在让我们的Entity进入图片。请注意，Entity只是我们的案例类

Entity是我们进行crud操作的case class。为了找到我们的实体，我们也可以使用Id。 Id对于在数据库中查找和操作实体或记录非常重要。此外Id实体的唯一标识

EntityActionsLike.scala

import slick.backend.DatabaseConfig
import slick.driver.JdbcProfile

import scala.concurrent.ExecutionContext

trait EntityActionsLike extends CrudActions {
  val dbConfig: DatabaseConfig[JdbcProfile]
  import dbConfig.driver.api._

  type Entity

  type Id

  type Model = Entity

  def insert(entity: Entity)(implicit ec: ExecutionContext): DBIO[Id]

  def deleteById(id: Id)(implicit ec: ExecutionContext): DBIO[Int]

  def findById(id: Id)(implicit ec: ExecutionContext): DBIO[Entity]

  def findOptionById(id: Id)(implicit ec: ExecutionContext): DBIO[Option[Entity]]
}

import slick.ast.BaseTypedType import slick.backend.DatabaseConfig import slick.driver.JdbcProfile

导入scala.concurrent.ExecutionContext

现在让我们实现这些方法。要进行操作，我们需要Table和TableQuery。假设我们有table和tableQuery。关于特征的好处是我们可以声明一个契约并将实现细节留给子类或子类

EntityActions.scala

trait EntityActions extends EntityActionsLike {
  val dbConfig: DatabaseConfig[JdbcProfile]
  import dbConfig.driver.api._

  type EntityTable <: Table[Entity]

  def tableQuery: TableQuery[EntityTable]

  def $id(table: EntityTable): Rep[Id]

  def modelIdContract: ModelIdContract[Entity,Id]

  override def count: DBIO[Int] = tableQuery.size.result

  override def insert(entity: Entity)(implicit ec: ExecutionContext): DBIO[Id] = {
    tableQuery.returning(tableQuery.map($id(_))) += entity
  }

  override def deleteById(id: Id)(implicit ec: ExecutionContext): DBIO[Int] = {
    filterById(id).delete
  }

  override def findById(id: Id)(implicit ec: ExecutionContext): DBIO[Entity] = {
    filterById(id).result.head
  }

  override def findOptionById(id: Id)(implicit ec: ExecutionContext): DBIO[Option[Entity]] = {
    filterById(id).result.headOption
  }

  override def save(model: Entity)(implicit ec: ExecutionContext): DBIO[Entity] = {
    insert(model).flatMap { id =>
      filterById(id).result.head
    }.transactionally
  }

  override def update(model: Entity)(implicit ec: ExecutionContext): DBIO[Entity] = {
    filterById(modelIdContract.get(model)).update(model).map { _ => model }.transactionally
  }

  override def delete(model: Entity)(implicit ec: ExecutionContext): DBIO[Int] = {
    filterById(modelIdContract.get(model)).delete
  }

  override def fetchAll(fetchSize: Int)(implicit ec: ExecutionContext): StreamingDBIO[Seq[Entity], Entity] = {
    tableQuery.result.transactionally.withStatementParameters(fetchSize = fetchSize)
  }

  def filterById(id: Id) = tableQuery.filter($id(_) === id)

  def baseTypedType: BaseTypedType[Id]

  protected implicit lazy val btt: BaseTypedType[Id] = baseTypedType

}

ActiveRecord.scala

import slick.dbio.DBIO

import scala.concurrent.ExecutionContext


abstract class ActiveRecord[R <: CrudActions](val repo: R) {
  def model: repo.Model
  def save()(implicit ec: ExecutionContext): DBIO[repo.Model] = repo.save(model)
  def update()(implicit ec: ExecutionContext): DBIO[repo.Model] = repo.update(model)
  def delete()(implicit ec: ExecutionContext): DBIO[Int] = repo.delete(model)
}

ModelContract.scala

case class ModelIdContract[A, B](get: A => B, set: (A, B) => A)

如何使用

Sample.scala

import com.google.inject.{Inject, Singleton}
import play.api.db.slick.DatabaseConfigProvider
import slick.ast.BaseTypedType
import slick.backend.DatabaseConfig
import slick.driver.JdbcProfile
import slick.{ActiveRecord, EntityActions, ModelIdContract}

case class Dog(name: String, id: Option[Long] = None)

@Singleton
class DogActiveRecord @Inject() (databaseConfigProvider: DatabaseConfigProvider) extends EntityActions {

  override val dbConfig: DatabaseConfig[JdbcProfile] = databaseConfigProvider.get[JdbcProfile]

  import dbConfig.driver.api._

  override def tableQuery = TableQuery(new Dogs(_))

  override def $id(table: Dogs): Rep[Id] = table.id

  override def modelIdContract: ModelIdContract[Dog, Id] = ModelIdContract(dog => dog.id.get, (dog, id) => dog.copy(id = Some(id)))

  override def baseTypedType: BaseTypedType[Id] = implicitly[BaseTypedType[Id]]

  override type Entity = Dog
  override type Id = Long
  override type EntityTable = Dogs

  class Dogs(tag: Tag) extends Table[Dog](tag, "DogsTable") {
    def name = column[String]("name")
    def id = column[Long]("id", O.PrimaryKey)
    def * = (name, id.?) <> (Dog.tupled, Dog.unapply)
  }

  implicit class ActiveRecordImplicit(val model: Entity) extends ActiveRecord(this)

  import scala.concurrent.ExecutionContext.Implicits.global

  val result = Dog("some_dog").save()

  val res2 = Dog("some_other_dog", Some(1)).delete()

  val res3 = Dog("some_crazy_dog", Some(1)).update()
}

现在我们可以像{

}一样直接对Dog进行操作

Dog("some_dog").save()

这隐含了我们的魔力

implicit class ActiveRecordImplicit(val model: Entity) extends ActiveRecord(this)

您还可以在EntityActions中添加scheme创建和删除逻辑

tableQuery.schema.create
table.schema.drop

Scala / Slick：使用继承和mixins来减少样板

1 个答案: