[SPARK-22950][SQL] Handle ChildFirstURLClassLoader's parent

## What changes were proposed in this pull request?

ChildFirstClassLoader's parent is set to null, so we can't get jars from its parent. This will cause ClassNotFoundException during HiveClient initialization with builtin hive jars, where we may should use spark context loader instead.

## How was this patch tested?

add new ut
cc cloud-fan gatorsmile

Author: Kent Yao <[email protected]>

Closes #20145 from yaooqinn/SPARK-22950.

Author: yaooqinn

sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveUtils.scala

@@ -47,7 +47,7 @@ import org.apache.spark.sql.internal.SQLConf
 import org.apache.spark.sql.internal.SQLConf._
 import org.apache.spark.sql.internal.StaticSQLConf.{CATALOG_IMPLEMENTATION, WAREHOUSE_PATH}
 import org.apache.spark.sql.types._
-import org.apache.spark.util.Utils
+import org.apache.spark.util.{ChildFirstURLClassLoader, Utils}
 
 
 private[spark] object HiveUtils extends Logging {
@@ -312,6 +312,8 @@ private[spark] object HiveUtils extends Logging {
       // starting from the given classLoader.
       def allJars(classLoader: ClassLoader): Array[URL] = classLoader match {
         case null => Array.empty[URL]
+        case childFirst: ChildFirstURLClassLoader =>
+          childFirst.getURLs() ++ allJars(Utils.getSparkClassLoader)
         case urlClassLoader: URLClassLoader =>
           urlClassLoader.getURLs ++ allJars(urlClassLoader.getParent)
         case other => allJars(other.getParent)

sql/hive/src/test/scala/org/apache/spark/sql/hive/HiveUtilsSuite.scala

@@ -17,11 +17,16 @@
 
 package org.apache.spark.sql.hive
 
+import java.net.URL
+
 import org.apache.hadoop.hive.conf.HiveConf.ConfVars
 
+import org.apache.spark.SparkConf
+import org.apache.spark.deploy.SparkHadoopUtil
 import org.apache.spark.sql.QueryTest
 import org.apache.spark.sql.hive.test.TestHiveSingleton
 import org.apache.spark.sql.test.SQLTestUtils
+import org.apache.spark.util.{ChildFirstURLClassLoader, MutableURLClassLoader}
 
 class HiveUtilsSuite extends QueryTest with SQLTestUtils with TestHiveSingleton {
 
@@ -42,4 +47,19 @@ class HiveUtilsSuite extends QueryTest with SQLTestUtils with TestHiveSingleton
       assert(hiveConf("foo") === "bar")
     }
   }
+
+  test("ChildFirstURLClassLoader's parent is null, get spark classloader instead") {
+    val conf = new SparkConf
+    val contextClassLoader = Thread.currentThread().getContextClassLoader
+    val loader = new ChildFirstURLClassLoader(Array(), contextClassLoader)
+    try {
+      Thread.currentThread().setContextClassLoader(loader)
+      HiveUtils.newClientForMetadata(
+        conf,
+        SparkHadoopUtil.newConfiguration(conf),
+        HiveUtils.newTemporaryConfiguration(useInMemoryDerby = true))
+    } finally {
+      Thread.currentThread().setContextClassLoader(contextClassLoader)
+    }
+  }
 }