fix serialization

features/src/main/scala/org/apache/spark/ml/SparkDefaultParamsReadWrite.scala

@@ -85,8 +85,31 @@ case object SparkDefaultParamsReadWrite {
  * @param expectedClassName If non empty, this is checked against the loaded metadata.
  * @throws IllegalArgumentException if expectedClassName is specified and does not match metadata
  */
- def parseMetadata(metadataStr: String, expectedClassName: String = ""): Metadata =
- DefaultParamsReader.parseMetadata(metadataStr)
+ def parseMetadata(metadataStr: String, expectedClassName: String = ""): Metadata = {
+ val metadata = parse(metadataStr)
+
+ implicit val format = DefaultFormats
+ val className = (metadata \ "class").extract[String]
+ val uid = (metadata \ "uid").extract[String]
+ val timestamp = (metadata \ "timestamp").extract[Long]
+ val sparkVersion = (metadata \ "sparkVersion").extract[String]
+ val params = metadata \ "paramMap"
+ val defaultParams = metadata \ "defaultParamMap"
+ if (expectedClassName.nonEmpty) {
+ require(className == expectedClassName, s"Error loading metadata: Expected class name" +
+ s" $expectedClassName but found class name $className")
+ }
+ // ******************************************************************************************
+ /**
+ * Backward compatible fix for models trained with older versions of Spark (prior to 2.4.x).
+ * The change introduced in https://github.com/apache/spark/pull/20633 added serialization of
+ * default params, older models won't have them and fail to load.
+ */
+ val defaultParamsFix = if (defaultParams == JNothing) JObject() else defaultParams
+ // ******************************************************************************************
+
+ new Metadata(className, uid, timestamp, sparkVersion, params, defaultParamsFix, metadata, metadataStr)
+ }
 
  /**
  * Extract Params from metadata, and set them in the instance.