Using standard java object persistence mechanism. / published by https://github.com/dacr/code-examples-manager #73d73891-599c-4bc2-bc15-4be8f2ca19c7/465a0e765705b39a861908dcbdf7f8f52ecb5675

object-persistence.sc

// summary : Using standard java object persistence mechanism.
// keywords : scala, java, persistence, scalatest
// publish : gist
// authors : David Crosson
// license : Apache NON-AI License Version 2.0 (https://raw.githubusercontent.com/non-ai-licenses/non-ai-licenses/main/NON-AI-APACHE2)
// id : 73d73891-599c-4bc2-bc15-4be8f2ca19c7
// created-on : 2020-05-31T19:54:52Z
// managed-by : https://github.com/dacr/code-examples-manager
// run-with : scala-cli $file

// ---------------------
//> using scala  "3.3.0"
//> using dep "org.scalatest::scalatest:3.2.16"
//> using objectWrapper
// ---------------------
import org.scalatest._, flatspec._, matchers._

import java.io._
import java.util.Date
import java.time.Instant


case class A(message:String)
case class B(a:A, report:String)

case class T1(
  t1:List[String],
  date:Date,
  instant:Instant,
  a1:Vector[A]
)

case class T2(
  t1:Array[String]
)

class ObjectPersistenceTest extends AnyFlatSpec with should.Matchers {
  override def suiteName="ObjectPersistence"

  def save(filename:String, that:Any):Unit = {
    val output = new ObjectOutputStream(new FileOutputStream(filename))
    output.writeObject(that)
    output.close()
  }
  def restore[THAT](filename:String):THAT = {
    val input = new ObjectInputStream(new FileInputStream(filename))
    input.readObject().asInstanceOf[THAT]
  }

  // --------------------------------------------------------------------------------
  "java persistence" should "be able to save and load scala case classes" in {
    val filename = "object-persistence.tmp"

    val b = new B(new A("This is A."), "This is B.")
    save(filename, b)
    restore[B](filename) should be(b)
  }

  // --------------------------------------------------------------------------------
  it should "even save and load more complex data structures" in {
    val filename = "object-persistence.tmp"
    val t = T1(
      List("1", "2", "3"),
      new Date(),
      Instant.now(),
      Vector(A("a1"),A("a2"))
    )
    save(filename, t)
    restore[T1](filename) should be(t)
  }

  // --------------------------------------------------------------------------------
  it should "work with array but take care of deep equalities within scalatest and arrays... :(" in {
    val filename = "object-persistence.tmp"

    val arr1 = Array("1", "2", "3")
    save(filename, arr1)
    restore[Array[String]](filename) shouldBe arr1

    val arr2 = T2(Array("1", "2", "3"))
    save(filename, arr2)
    //restore[T2](filename) shouldBe arr2 // fail

    val arr3 = T2(Array("1", "2", "3"))
    save(filename, arr3)
    restore[T2](filename).t1 shouldEqual arr3.t1

  }
}

org.scalatest.tools.Runner.main(Array("-oDF", "-s", classOf[ObjectPersistenceTest].getName))