play framework anorm orm 化构想

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play 框架引入了一个简单的数据库访问层:anorm。

使用anorm做模型层,代码大致如下:

 

case class Dog(id: Pk[Long], name: String, age: String)

object Dog {
  val simple = get[Pk[Long]]("dog.id") ~ str("name") ~ int("age") map {
    case id ~ name ~ age => Dog(id, name, age)
  }

  def findById(id: Long) = DB.withConnection {
    implicit connection =>
      SQL("select * from dog where id = {id}").on('id -> id).as(Dog.simple.singleOpt)
  }

  def create(dog: Dog) = DB.withConnection {
    implicit connection =>
      val idOpt: Option[Long] = SQL(
        """
          insert into dog (name, age)
          values ({name}, {age})
        """
      ).on(
        'name -> dog.name,
        'age -> dog.age
      ).executeInsert()
      val result = dog.copy(id = Id(idOpt.get))
      result
  }

  def update(id: Long, dog: Dog) = DB.withConnection {
    implicit connection =>
      SQL(
        """
        update dog set name = {name}, age = {age} where id = {id}
        """
      ).on(
        'id -> id,
        'name -> dog.name,
        'age -> dog.age
      ).executeUpdate()
  }

}

 

 

    明显比JPA繁杂,那么,有没有办法封装下anorm,使它更象orm,提供更好的维护性,更快的开发速度?

    在scala 2.10中,引入的试验性功能:macro, reflection,或许就是问题的答案(现在只是一个构想,会抽空实现验证下),还是代码为先:

 

trait Modal[T] {
  val simple = macro ModalMacroImpl.simple[T]
  def findById(id: Long): Option[T] = macro ModalMacroImpl.find
  def create(o: T) = macro ModalMacroImpl.create
  def update(id: Long, o: T) = macro ModalMacroImpl.update
  def list = macro ModalMacroImpl.list
}

object Dog extends Modal[Dog] {
  def findByName(name: String): Option[T] = macro ModalMacroImpl.find
}

 

 

通过Modal及提供的macro,简化了model的定义。

ModalMacroImpl可以通过reflaction实现,并且macro是编译时增强的,不会对性能造成影响。

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