Serialization / Deserialization

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Scala

有一篇比较各种库性能的文章：
Scala Serialization

pickling

参考：

• https://github.com/scala/pickling
• On Pickles & Spores: Improving Support for Distributed Programming in Scala

pickling是最方便的序列化库，可以直接支持大部分的Scala数据类型。

基本用例

import scala.pickling.Defaults._
import scala.pickling.binary._
val d = new DateTime()
val pckl = d.pickle
val bytes = pckl.value  // 序列化成字节
println(s"bytes length = ${bytes.length}")
val obj = BinaryPickle(bytes).unpickle[DateTime]
println(s"obj = $obj") //  从字节数组反序列化回来

Customized Picker/Unpicker

先看个最基本的case class的pickler/unpickler

import scala.pickling.tags.FastTypeTag
import scala.pickling.binary._
import scala.pickling.Defaults._
import scala.pickling._
case class Foo(val x: String, y: Int, z: String)
object CustomerPicklerUnpicklers {
  implicit object FooPickler extends AbstractPicklerUnpickler[Foo] {
    //  不需要写 stringPickler,写了的话会报错, 以为已经存在PrimitivePicklers.stringPickler
    val stringUnpickler = implicitly[Unpickler[String]]   // 但是不存在stringUnpickler
    val intUnpickler    = implicitly[Unpickler[Int]]
    override val tag = FastTypeTag[Foo]
    override def pickle(foo: Foo, builder: PBuilder): Unit = {
      println(s"Pickling Foo ...")
      builder.beginEntry(foo, tag)
      builder.putField("x",  b => stringPickler.pickle(foo.x , b))
      builder.putField("y",  b => intPickler.pickle(foo.y    , b))
      builder.putField("z",  b => stringPickler.pickle(foo.z , b))
      builder.endEntry()
    }
    override def unpickle(tag: String, reader: PReader): Foo = {
      println("Unpickling Foo ...")
      val x = stringUnpickler.unpickleEntry(reader.readField("x")).asInstanceOf[String]
      val y = intUnpickler.unpickleEntry(reader.readField("y")).asInstanceOf[Int]
      val z = stringUnpickler.unpickleEntry(reader.readField("z")).asInstanceOf[String]
      Foo(x, y, z)
    }
  }
}
object  TestFoo {
  import CustomerPicklerUnpicklers._
  def main(args: Array[String]): Unit = {
    val foo  = Foo("Hello", 100, null) // 支持null
    val pckl = foo.pickle
    val bytes = pckl.value
    println(s"length = ${bytes.length}")
    val obj = BinaryPickle(bytes).unpickle[Foo]
    println(obj)
  }
}

输出为

Pickling Foo ...
length = 79
Unpickling Foo ...
Foo(Hello,100,null)