Immutable Domain Model with JPA

Immutable domain model in Scala

// Sketch of an immutable domain model in Scala

// We used this scheme together with this JPA module: 
//    http://github.com/jboner/skalman/blob/d1e03a85be3964b9012f9e79dd726b0546342b2b/core/src/main/scala/JPA.scala
// ...and this GenericRepository: 
//    http://github.com/jboner/skalman/blob/d1e03a85be3964b9012f9e79dd726b0546342b2b/core/src/main/scala/GenericRepository.scala

abstract class Entity[T](val id: Int)

object User {
  private val identityMap = new ConcurrentHashMap[Int, User]
  def apply(id: Int) = identityMap.get(id)
  def update(user: User) = identityMap.put(user.id, user)
  
  // add generic repository stuff
}
  
class User(id: Int, val username: String, val password: String) extends Entity(id) {
  User.update(this)
  def withUsername(username: String): User = new User(id, username, password)
  def withPassword(password: String): User = new User(id, username, password)
}

val updatedUser = User(34).withUsername("bill").withPassword("secret")