HDFS-8686. WebHdfsFileSystem#getXAttr(Path p, final String name) doesn't work if namespace is in capitals (Contributed by kanaka kumar avvaru)

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/web/JsonUtilClient.java

@@ -413,6 +413,20 @@ class JsonUtilClient {
     return null;
   }
 
+  /** Expecting only single XAttr in the map. return its value */
+  static byte[] getXAttr(final Map<?, ?> json) throws IOException {
+    if (json == null) {
+      return null;
+    }
+
+    Map<String, byte[]> xAttrs = toXAttrs(json);
+    if (xAttrs != null && !xAttrs.values().isEmpty()) {
+      return xAttrs.values().iterator().next();
+    }
+
+    return null;
+  }
+
   static Map<String, byte[]> toXAttrs(final Map<?, ?> json)
       throws IOException {
     if (json == null) {

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/web/WebHdfsFileSystem.java

@@ -963,7 +963,7 @@ public class WebHdfsFileSystem extends FileSystem
         new XAttrEncodingParam(XAttrCodec.HEX)) {
       @Override
       byte[] decodeResponse(Map<?, ?> json) throws IOException {
-        return JsonUtilClient.getXAttr(json, name);
+        return JsonUtilClient.getXAttr(json);
       }
     }.run();
   }

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

@@ -1005,6 +1005,9 @@ Release 2.8.0 - UNRELEASED
     HDFS-8577. Avoid retrying to recover lease on a file which does not exist
     (J.Andreina via vinayakumarb)
 
+    HDFS-8686. WebHdfsFileSystem#getXAttr(Path p, final String name) doesn't
+    work if namespace is in capitals (kanaka kumar avvaru via vinayakumarb)
+
 Release 2.7.2 - UNRELEASED
 
   INCOMPATIBLE CHANGES

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

@@ -395,7 +395,10 @@ public class FSXAttrBaseTest {
     FileSystem.mkdirs(fs, path, FsPermission.createImmutable((short)0750));
     fs.setXAttr(path, name1, value1, EnumSet.of(XAttrSetFlag.CREATE));
     fs.setXAttr(path, name2, value2, EnumSet.of(XAttrSetFlag.CREATE));
-    
+
+    final byte[] theValue = fs.getXAttr(path, "USER.a2");
+    Assert.assertArrayEquals(value2, theValue);
+
     /* An XAttr that was requested does not exist. */
     try {
       final byte[] value = fs.getXAttr(path, name3);

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/tools/offlineImageViewer/TestOfflineImageViewerForXAttr.java

@@ -231,6 +231,9 @@ public class TestOfflineImageViewerForXAttr {
           "user.attr1"));
       assertEquals("value1", value);
 
+      value = new String(webhdfs.getXAttr(new Path("/dir1"), "USER.attr1"));
+      assertEquals("value1", value);
+
       Map<String, byte[]> contentMap = webhdfs.getXAttrs(new Path("/dir1"),
           names);