8353662: Add test for non-local file URL fallback to FTP

Reviewed-by: dfuchs

Author: Eirik Bjørsnøs

test/jdk/sun/net/www/protocol/file/NonLocalFtpFallback.java

@@ -0,0 +1,145 @@
+/*
+ * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+import com.sun.net.httpserver.HttpExchange;
+import com.sun.net.httpserver.HttpHandler;
+import com.sun.net.httpserver.HttpServer;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.net.*;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.HashSet;
+import java.util.Random;
+import java.util.Set;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+/**
+ * @test
+ * @bug 8353662
+ * @summary Verify long-standing behavior of resolving non-local file URLs using FTP.
+ * @run junit NonLocalFtpFallback
+ */
+
+public class NonLocalFtpFallback {
+
+    // Port 21 may not be available, use an HTTP proxy with an ephemeral port
+    private HttpServer proxyServer;
+
+    // The file requested in this test
+    private Path file;
+
+    // FTP URIs requested by the proxy client
+    private Set<URI> uris = new HashSet<>();
+
+    /**
+     * Set up the HTTP proxy used for serving FTP in this test
+     *
+     * @throws IOException if an unexpected IO error occurs
+     */
+    @BeforeEach
+    public void setup() throws IOException {
+        // Create a file with some random data
+        byte[] data = new byte[512];
+        new Random().nextBytes(data);
+        file = Files.write(Path.of("ftp-file.txt"), data);
+
+        // Set up an HTTP proxy server
+        proxyServer = HttpServer.create();
+        // Bind to the loopback address with an ephemeral port
+        InetAddress loopbackAddress = InetAddress.getLoopbackAddress();
+        proxyServer.bind(new InetSocketAddress(loopbackAddress, 0), 0);
+        // Handler for the FTP proxy request
+        proxyServer.createContext("/", new HttpHandler() {
+            @Override
+            public void handle(HttpExchange exchange) throws IOException {
+                // Record the URI requested
+                uris.add(exchange.getRequestURI());
+                // Send the data
+                exchange.sendResponseHeaders(200, Files.size(file));
+                try (OutputStream out = exchange.getResponseBody()) {
+                    Files.copy(file, out);
+                }
+                // Complete the exchange
+                exchange.close();
+            }
+        });
+        // Start the proxy server
+        proxyServer.start();
+    }
+
+    /**
+     * Shut down proxy server and clean up files created
+     *
+     * @throws IOException if an unexpected IO error occurs
+     */
+    @AfterEach
+    public void destroy() throws IOException {
+        proxyServer.stop(2);
+        Files.delete(file);
+    }
+
+    /**
+     * Verifies the long-standing and unspecified FTP fallback feature where the file
+     * URL scheme handler attempts an FTP connection for non-local files.
+     *
+     * The non-local file URL used here is of the form file://127.0.0.1/path. Since the
+     * host component here is not equal to "localhost", this is considered a non-local
+     * URL.
+     *
+     * @throws Exception
+     */
+    @Test
+    public void verifyNonLocalFtpFallback() throws Exception {
+        URL localURL = file.toUri().toURL();
+        // We can use a fake host name here, no actual FTP request will be made
+        String hostname = "remotehost";
+        URL nonLocalURL = new URL("file", hostname, localURL.getFile());
+
+        // Open the non-local file: URL connection using a proxy
+        Proxy proxy = new Proxy(Proxy.Type.HTTP,
+                new InetSocketAddress(proxyServer.getAddress().getAddress(),
+                        proxyServer.getAddress().getPort()));
+        URLConnection con = nonLocalURL.openConnection(proxy);
+
+        // Assert that the expected file content is retrieved
+        try (InputStream in = con.getInputStream()) {
+            byte[] retrived = in.readAllBytes();
+            assertArrayEquals(Files.readAllBytes(file), retrived);
+        }
+
+        // Assert that the expected FTP URI was requested in the HTTP proxy
+        assertEquals(1, uris.size());
+        URL ftpURL = new URL("ftp", hostname, localURL.getFile());
+        assertEquals(ftpURL.toURI(), uris.iterator().next());
+    }
+}