HDFS-5908. Change AclFeature to capture list of ACL entries in an ImmutableList. Contributed by Chris Nauroth.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1572142 13f79535-47bb-0310-9956-ffa450edef68

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -336,6 +336,9 @@ Trunk (Unreleased)
     checks are disabled, user is superuser or user is member of supergroup.
     (cnauroth)
 
+    HDFS-5908. Change AclFeature to capture list of ACL entries in an
+    ImmutableList. (cnauroth)
+
 Release 2.5.0 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/AclFeature.java

@@ -18,26 +18,26 @@
 
 package org.apache.hadoop.hdfs.server.namenode;
 
-import java.util.Collections;
-import java.util.List;
-
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.fs.permission.AclEntry;
 
+import com.google.common.collect.ImmutableList;
+
 /**
  * Feature that represents the ACLs of the inode.
  */
 @InterfaceAudience.Private
 public class AclFeature implements INode.Feature {
-  public static final List<AclEntry> EMPTY_ENTRY_LIST = Collections.emptyList();
+  public static final ImmutableList<AclEntry> EMPTY_ENTRY_LIST =
+    ImmutableList.of();
 
-  private final List<AclEntry> entries;
+  private final ImmutableList<AclEntry> entries;
 
-  public AclFeature(List<AclEntry> entries) {
+  public AclFeature(ImmutableList<AclEntry> entries) {
     this.entries = entries;
   }
 
-  public List<AclEntry> getEntries() {
+  public ImmutableList<AclEntry> getEntries() {
     return entries;
   }
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/AclStorage.java

@@ -328,7 +328,7 @@ final class AclStorage {
 
     // Add all default entries to the feature.
     featureEntries.addAll(defaultEntries);
-    return new AclFeature(Collections.unmodifiableList(featureEntries));
+    return new AclFeature(ImmutableList.copyOf(featureEntries));
   }
 
   /**

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/FSAclBaseTest.java

@@ -48,6 +48,7 @@ import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
 
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Lists;
 
 /**
@@ -1272,6 +1273,12 @@ public abstract class FSAclBaseTest {
     AclFeature aclFeature = inode.getAclFeature();
     if (expectAclFeature) {
       assertNotNull(aclFeature);
+      // Intentionally capturing a reference to the entries, not using nested
+      // calls.  This way, we get compile-time enforcement that the entries are
+      // stored in an ImmutableList.
+      ImmutableList<AclEntry> entries = aclFeature.getEntries();
+      assertNotNull(entries);
+      assertFalse(entries.isEmpty());
     } else {
       assertNull(aclFeature);
     }