Revert "Disable caching for JarURLConnection to avoid sharing JarFile with other users when loading resource from URL in Configuration class. Contributed by Zhihai Xu"

This reverts commit e690a32e57bc14b0cca0e2d39da513841d81b4fc.

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -782,10 +782,6 @@ Release 2.8.0 - UNRELEASED
     HADOOP-12413. AccessControlList should avoid calling getGroupNames in
     isUserInList with empty groups. (Zhihai Xu via cnauroth)
 
-    HADOOP-12404. Disable caching for JarURLConnection to avoid sharing
-    JarFile with other users when loading resource from URL in Configuration
-    class. (zxu)
-
   OPTIMIZATIONS
 
     HADOOP-11785. Reduce the number of listStatus operation in distcp

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/conf/Configuration.java

@@ -34,9 +34,7 @@ import java.io.Reader;
 import java.io.Writer;
 import java.lang.ref.WeakReference;
 import java.net.InetSocketAddress;
-import java.net.JarURLConnection;
 import java.net.URL;
-import java.net.URLConnection;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
@@ -2533,14 +2531,7 @@ public class Configuration implements Iterable<Map.Entry<String,String>>,
     if (url == null) {
       return null;
     }
-
-    URLConnection connection = url.openConnection();
-    if (connection instanceof JarURLConnection) {
-      // Disable caching for JarURLConnection to avoid sharing JarFile
-      // with other users.
-      connection.setUseCaches(false);
-    }
-    return parse(builder, connection.getInputStream(), url.toString());
+    return parse(builder, url.openStream(), url.toString());
   }
 
   private Document parse(DocumentBuilder builder, InputStream is,