HADOOP-17870 Make Http Filesystem allow non-absolute uri based paths.

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/http/AbstractHttpFileSystem.java

@@ -60,7 +60,8 @@ public URI getUri() {
 
   @Override
   public FSDataInputStream open(Path path, int bufferSize) throws IOException {
-    URLConnection conn = path.toUri().toURL().openConnection();
+    URI pathUri = makeQualified(path).toUri();
+    URLConnection conn = pathUri.toURL().openConnection();
     InputStream in = conn.getInputStream();
     return new FSDataInputStream(new HttpDataInputStream(in));
   }

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/http/TestHttpFileSystem.java

@@ -33,6 +33,7 @@
 import java.net.URISyntaxException;
 import java.net.URL;
 import java.nio.charset.StandardCharsets;
+import java.util.stream.IntStream;
 
 import static org.junit.Assert.assertEquals;
 
@@ -48,20 +49,26 @@ public void testHttpFileSystem() throws IOException, URISyntaxException,
     final String data = "foo";
 
     try (MockWebServer server = new MockWebServer()) {
-      server.enqueue(new MockResponse().setBody(data));
+      IntStream.rangeClosed(1, 3).forEach(i -> server.enqueue(new MockResponse().setBody(data)));
       server.start();
       URI uri = URI.create(String.format("http://%s:%d", server.getHostName(),
           server.getPort()));
       FileSystem fs = FileSystem.get(uri, conf);
-      try (InputStream is = fs.open(
-          new Path(new URL(uri.toURL(), "/foo").toURI()),
-          4096)) {
-        byte[] buf = new byte[data.length()];
-        IOUtils.readFully(is, buf, 0, buf.length);
-        assertEquals(data, new String(buf, StandardCharsets.UTF_8));
-      }
+      assertSameData(fs, new Path(new URL(uri.toURL(), "/foo").toURI()), data);
+      assertSameData(fs, new Path("/foo"), data);
+      assertSameData(fs, new Path("foo"), data);
       RecordedRequest req = server.takeRequest();
       assertEquals("/foo", req.getPath());
     }
   }
+
+  private void assertSameData(FileSystem fs, Path path, String data) throws IOException {
+    try (InputStream is = fs.open(
+            path,
+            4096)) {
+      byte[] buf = new byte[data.length()];
+      IOUtils.readFully(is, buf, 0, buf.length);
+      assertEquals(data, new String(buf, StandardCharsets.UTF_8));
+    }
+  }
 }