build.sbt

scalaVersion := "2.10.4"

libraryDependencies += "com.esotericsoftware.kryo" % "kryo" % sys.env.getOrElse("KRYO_VERSION", "2.21")

KryoTest.scala

import com.esotericsoftware.kryo.Kryo
import com.esotericsoftware.kryo.serializers.JavaSerializer
import com.esotericsoftware.kryo.io.{Input, Output}

class JavaSerializable extends Serializable

object KryoTest {

  def main(args: Array[String]): Unit = {
    val kryo = new Kryo()
    kryo.register(classOf[JavaSerializable], new JavaSerializer())
    var output = new Output(100, 100)

    val objectToWrite = new JavaSerializable

    kryo.writeClassAndObject(output, objectToWrite)
    val firstWriteBytes = output.toBytes
    println("First size is " + firstWriteBytes.length)
    kryo.readClassAndObject(new Input(firstWriteBytes))
    println("Successfully deserialized first copy")

    //output = new Output(100, 100)
    output.clear()
    kryo.reset()

    kryo.writeClassAndObject(output, objectToWrite)
    val secondWriteBytes = output.toBytes
    println("Second size is " + secondWriteBytes.length)
    kryo.readClassAndObject(new Input(secondWriteBytes))
    println("Successfully deserialized second copy")
  }

}

When I run this in sbt:

> run
[info] Compiling 1 Scala source to /Users/joshrosen/Documents/kryo-output-bug/target/scala-2.10/classes...
[info] Running KryoTest
First size is 39
Successfully deserialized first copy
Second size is 36
[error] (run-main-5) com.esotericsoftware.kryo.KryoException: Error during Java deserialization.
com.esotericsoftware.kryo.KryoException: Error during Java deserialization.
    at com.esotericsoftware.kryo.serializers.JavaSerializer.read(JavaSerializer.java:42)
    at com.esotericsoftware.kryo.Kryo.readClassAndObject(Kryo.java:729)
    at KryoTest$.main(KryoTest.scala:29)
    at KryoTest.main(KryoTest.scala)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
Caused by: java.io.StreamCorruptedException: invalid stream header: 79737200
    at java.io.ObjectInputStream.readStreamHeader(ObjectInputStream.java:804)
    at java.io.ObjectInputStream.<init>(ObjectInputStream.java:299)
    at com.esotericsoftware.kryo.serializers.JavaSerializer.read(JavaSerializer.java:40)
    at com.esotericsoftware.kryo.Kryo.readClassAndObject(Kryo.java:729)
    at KryoTest$.main(KryoTest.scala:29)
    at KryoTest.main(KryoTest.scala)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)

The second deserialization crashes.