forgo uid and eager ser

core/src/main/scala/org/apache/spark/util/Lazy.scala

@@ -16,8 +16,6 @@
  */
 package org.apache.spark.util
 
-import java.io.ObjectOutputStream
-
 /**
  * Construct to lazily initialize a variable.
  * This may be helpful for avoiding deadlocks in certain scenarios. For example,
@@ -27,17 +25,11 @@ import java.io.ObjectOutputStream
  *      the parent object.
  *   c) If thread 1 waits for thread 2 to join, a deadlock occurs.
  */
-@SerialVersionUID(7964587975756091988L)
 private[spark] class Lazy[T](initializer: => T) extends Serializable {
 
   private[this] lazy val value: T = initializer
 
   def apply(): T = {
     value
   }
-
-  private def writeObject(stream: ObjectOutputStream): Unit = {
-    this.value // ensure value is initialized
-    stream.defaultWriteObject()
-  }
 }

core/src/test/scala/org/apache/spark/util/LazySuite.scala

@@ -16,29 +16,11 @@
  */
 package org.apache.spark.util
 
-import java.io.{ByteArrayInputStream, ByteArrayOutputStream, NotSerializableException, ObjectInputStream, ObjectOutputStream}
-import java.util.Base64
+import java.io.{ByteArrayOutputStream, NotSerializableException, ObjectOutputStream}
 
 import org.apache.spark.SparkFunSuite
 
-@SerialVersionUID(2108928072825530631L)
-case class LazyUsage() extends Serializable {
-  private val lazyString = new Lazy(LazyFunction.GetString())
-  def getLazyString(): String = lazyString()
-}
-
-object LazyFunction {
-  def GetString(): String = "hello world"
-}
-
 class LazySuite extends SparkFunSuite {
-  // This is generated with an old version (lamda is serialized):
-  // 1, comment out the 'writeObject' method in Lazy.scala;
-  // 2, print the serialized base64 string of a LazyUsage instance.
-  // scalastyle:off
-  private val base64WithLambda = "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"
-  // scalastyle:on
-
   test("Lazy val works") {
     var test: Option[Object] = None
 
@@ -57,81 +39,22 @@ class LazySuite extends SparkFunSuite {
     assert(lazyval() == test && test.isDefined)
   }
 
-  test("Lazy val serialization fails if the dereferenced object is not serializable") {
+  test("Lazy val is serializable") {
     val lazyval = new Lazy({
       new Object()
     })
 
-    // Ensure we are not serializable after the dereference (type "Object" is not serializable)
-    intercept[NotSerializableException] {
-      val oos = new ObjectOutputStream(new ByteArrayOutputStream())
-      oos.writeObject(lazyval)
-    }
-  }
-
-  test("Lazy val serializes the value, even if dereference was never called") {
-    var times = 100
-    val lazyval = new Lazy({
-      val result = "0" * times
-      times = 0
-      result
-    })
+    // Ensure we are serializable before the dereference
+    val oos = new ObjectOutputStream(new ByteArrayOutputStream())
+    oos.writeObject(lazyval)
 
-    // Ensure we serialized the value even if it was never dereferenced
-    val base64str = serializeToBase64(lazyval)
-    assert(base64str.contains("MDAw" * 32)) // MDAw is the base64 encoding of "000"
-  }
+    @SuppressWarnings(Array("never used"))
+    val dereferenced = lazyval()
 
-  test("Lazy val serializes the value, if dereference was called") {
-    var times = 100
-    val lazyval = new Lazy({
-      val result = "0" * times
-      times = 0
-      result
-    })
-    val zeros = lazyval()
-    assert(zeros.length == 100)
-    // Ensure we serialized the same value
-    val base64str = serializeToBase64(lazyval)
-    assert(base64str.contains("MDAw" * 32)) // MDAw is the base64 encoding of "000"
-  }
-
-  test("Lazy val can be deserialized from lambda") {
-    val lazyObj = deserializeFromBase64[LazyUsage](base64WithLambda)
-    assert(lazyObj.getLazyString() === "hello world")
-  }
-
-  test("Lazy value round trip serialization works correctly") {
-    val lazyval = LazyUsage()
-    val serialized = serializeToBase64(lazyval)
-    val obj = deserializeFromBase64[LazyUsage](serialized)
-    assert(obj.getLazyString() === lazyval.getLazyString())
-  }
-
-  test("serialVersionUID was serialized and deserialized correctly") {
-    val lazyval = new Lazy("")
-    val serialized = serializeToBase64(lazyval)
-    val obj = deserializeFromBase64[Lazy[String]](serialized)
-    val field = obj.getClass.getDeclaredField("serialVersionUID")
-    field.setAccessible(true)
-    assert(field.getLong(obj) == 7964587975756091988L)
-  }
-
-  def serializeToBase64[T](o: T): String = {
-    val baos = new ByteArrayOutputStream
-    val oos = new ObjectOutputStream(baos)
-    try {
-      oos.writeObject(o)
-      Base64.getEncoder.encodeToString(baos.toByteArray)
-    } finally {
-      oos.close()
+    // Ensure we are not serializable after the dereference (type "Object" is not serializable)
+    intercept[NotSerializableException] {
+      val oos2 = new ObjectOutputStream(new ByteArrayOutputStream())
+      oos2.writeObject(lazyval)
     }
   }
-
-  def deserializeFromBase64[T](base64Str: String): T = {
-    val bytes = Base64.getDecoder.decode(base64Str)
-    val bais = new ByteArrayInputStream(bytes)
-    val ois = new ObjectInputStream(bais)
-    ois.readObject().asInstanceOf[T]
-  }
 }