--- a/src/java.base/share/classes/java/net/ProxySelector.java	Mon Aug 26 11:46:54 2019 +0100
+++ b/src/java.base/share/classes/java/net/ProxySelector.java	Mon Aug 26 12:25:49 2019 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2019, 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
@@ -143,7 +143,9 @@
      *          contain one element of type
      *          {@link java.net.Proxy Proxy}
      *          that represents a direct connection.
-     * @throws IllegalArgumentException if the argument is null
+     * @throws IllegalArgumentException if the argument is null or if
+     *         the protocol or host cannot be determined from the provided
+     *         {@code uri}
      */
     public abstract List<Proxy> select(URI uri);
 

--- a/src/java.base/share/classes/sun/net/www/protocol/ftp/FtpURLConnection.java	Mon Aug 26 11:46:54 2019 +0100
+++ b/src/java.base/share/classes/sun/net/www/protocol/ftp/FtpURLConnection.java	Mon Aug 26 12:25:49 2019 +0100
@@ -44,6 +44,7 @@
 import java.net.URI;
 import java.net.Proxy;
 import java.net.ProxySelector;
+import java.util.List;
 import java.util.StringTokenizer;
 import java.util.Iterator;
 import java.security.Permission;
@@ -242,7 +243,13 @@
                     });
             if (sel != null) {
                 URI uri = sun.net.www.ParseUtil.toURI(url);
-                Iterator<Proxy> it = sel.select(uri).iterator();
+                final List<Proxy> proxies;
+                try {
+                    proxies = sel.select(uri);
+                } catch (IllegalArgumentException iae) {
+                    throw new IOException("Failed to select a proxy", iae);
+                }
+                final Iterator<Proxy> it = proxies.iterator();
                 while (it.hasNext()) {
                     p = it.next();
                     if (p == null || p == Proxy.NO_PROXY ||

--- a/src/java.base/share/classes/sun/net/www/protocol/http/HttpURLConnection.java	Mon Aug 26 11:46:54 2019 +0100
+++ b/src/java.base/share/classes/sun/net/www/protocol/http/HttpURLConnection.java	Mon Aug 26 12:25:49 2019 +0100
@@ -1178,7 +1178,13 @@
                     if (logger.isLoggable(PlatformLogger.Level.FINEST)) {
                         logger.finest("ProxySelector Request for " + uri);
                     }
-                    Iterator<Proxy> it = sel.select(uri).iterator();
+                    final List<Proxy> proxies;
+                    try {
+                        proxies = sel.select(uri);
+                    } catch (IllegalArgumentException iae) {
+                        throw new IOException("Failed to select a proxy", iae);
+                    }
+                    final Iterator<Proxy> it = proxies.iterator();
                     Proxy p;
                     while (it.hasNext()) {
                         p = it.next();

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/jdk/java/net/HttpURLConnection/HttpURLProxySelectionTest.java	Mon Aug 26 12:25:49 2019 +0100
@@ -0,0 +1,156 @@
+/*
+ * Copyright (c) 2019, 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.testng.Assert;
+import org.testng.annotations.AfterTest;
+import org.testng.annotations.BeforeTest;
+import org.testng.annotations.Test;
+import sun.net.spi.DefaultProxySelector;
+
+import java.io.IOException;
+import java.net.HttpURLConnection;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.Proxy;
+import java.net.ProxySelector;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.net.URL;
+import java.util.List;
+
+/**
+ * @test
+ * @bug 6563286 6797318 8177648
+ * @summary Tests that sun.net.www.protocol.http.HttpURLConnection when dealing with
+ * sun.net.spi.DefaultProxySelector#select() handles any IllegalArgumentException
+ * correctly
+ * @run testng HttpURLProxySelectionTest
+ * @modules java.base/sun.net.spi:+open
+ */
+public class HttpURLProxySelectionTest {
+
+    private static final String WEB_APP_CONTEXT = "/httpurlproxytest";
+
+    private HttpServer server;
+    private SimpleHandler handler;
+    private ProxySelector previousDefault;
+    private CustomProxySelector ourProxySelector = new CustomProxySelector();
+
+    @BeforeTest
+    public void beforeTest() throws Exception {
+        previousDefault = ProxySelector.getDefault();
+        ProxySelector.setDefault(ourProxySelector);
+        handler = new SimpleHandler();
+        server = createServer(handler);
+    }
+
+    @AfterTest
+    public void afterTest() {
+        try {
+            if (server != null) {
+                final int delaySeconds = 0;
+                server.stop(delaySeconds);
+            }
+        } finally {
+            ProxySelector.setDefault(previousDefault);
+        }
+    }
+
+    /**
+     * - Test initiates a HTTP request to server
+     * - Server receives request and sends a 301 redirect to an URI which doesn't have a "host"
+     * - Redirect is expected to fail with IOException (caused by IllegalArgumentException from DefaultProxySelector)
+     *
+     * @throws Exception
+     */
+    @Test
+    public void test() throws Exception {
+        final String targetURL = "http://" + server.getAddress().getHostName() + ":"
+                + server.getAddress().getPort() + WEB_APP_CONTEXT;
+        System.out.println("Sending request to " + targetURL);
+        final HttpURLConnection conn = (HttpURLConnection) new URL(targetURL).openConnection();
+        try {
+            conn.getResponseCode();
+            Assert.fail("Request to " + targetURL + " was expected to fail during redirect");
+        } catch (IOException ioe) {
+            // expected because of the redirect to an invalid URL, for which a proxy can't be selected
+
+            // make sure the it was indeed a redirect
+            Assert.assertTrue(handler.redirectSent, "Server was expected to send a redirect, but didn't");
+            Assert.assertTrue(ourProxySelector.selectorUsedForRedirect, "Proxy selector wasn't used for redirect");
+
+            // make sure the IOException was caused by an IllegalArgumentException
+            Assert.assertTrue(ioe.getCause() instanceof IllegalArgumentException, "Unexpected cause in the IOException");
+        }
+    }
+
+
+    private static HttpServer createServer(final HttpHandler handler) throws IOException {
+        final InetSocketAddress serverAddr = new InetSocketAddress(InetAddress.getLoopbackAddress(), 0);
+        final int backlog = -1;
+        final HttpServer server = HttpServer.create(serverAddr, backlog);
+        // setup the handler
+        server.createContext(WEB_APP_CONTEXT, handler);
+        // start the server
+        server.start();
+        System.out.println("Server started on " + server.getAddress());
+        return server;
+    }
+
+    private static class SimpleHandler implements HttpHandler {
+        private boolean redirectSent = false;
+
+        @Override
+        public void handle(final HttpExchange httpExchange) throws IOException {
+            final String redirectURL;
+            try {
+                redirectURL = new URI("http", "/irrelevant", null).toString();
+            } catch (URISyntaxException e) {
+                throw new IOException(e);
+            }
+            httpExchange.getResponseHeaders().add("Location", redirectURL);
+            final URI requestURI = httpExchange.getRequestURI();
+            System.out.println("Handling " + httpExchange.getRequestMethod() + " request "
+                    + requestURI + " responding with redirect to " + redirectURL);
+            httpExchange.sendResponseHeaders(301, -1);
+            this.redirectSent = true;
+        }
+
+    }
+
+    private static class CustomProxySelector extends DefaultProxySelector {
+
+        private boolean selectorUsedForRedirect = false;
+
+        @Override
+        public List<Proxy> select(final URI uri) {
+            if (uri.toString().contains("/irrelevant")) {
+                this.selectorUsedForRedirect = true;
+            }
+            return super.select(uri);
+        }
+    }
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/jdk/sun/net/spi/DefaultProxySelectorTest.java	Mon Aug 26 12:25:49 2019 +0100
@@ -0,0 +1,90 @@
+/*
+ * Copyright (c) 2019, 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 org.testng.Assert;
+import org.testng.annotations.Test;
+import sun.net.spi.DefaultProxySelector;
+
+import java.net.ProxySelector;
+import java.net.URI;
+
+/**
+ * @test
+ * @bug 6563286 6797318 8177648
+ * @summary Tests sun.net.spi.DefaultProxySelector#select(URI)
+ * @run testng DefaultProxySelectorTest
+ * @modules java.base/sun.net.spi:+open
+ */
+public class DefaultProxySelectorTest {
+
+    /**
+     * Tests that {@link DefaultProxySelector#select(URI)} throws
+     * {@link IllegalArgumentException} when passed {@code null}
+     */
+    @Test
+    public void testIllegalArgForNull() {
+        final ProxySelector selector = new DefaultProxySelector();
+        try {
+            selector.select(null);
+            Assert.fail("select() was expected to fail for null URI");
+        } catch (IllegalArgumentException iae) {
+            // expected
+        }
+    }
+
+    /**
+     * Tests that {@link DefaultProxySelector} throws a {@link IllegalArgumentException}
+     * for URIs that don't have host information
+     *
+     * @throws Exception
+     */
+    @Test
+    public void testIllegalArgForNoHost() throws Exception {
+        final ProxySelector selector = new DefaultProxySelector();
+        assertFailsWithIAE(selector, new URI("http", "/test", null));
+        assertFailsWithIAE(selector, new URI("https", "/test2", null));
+        assertFailsWithIAE(selector, new URI("ftp", "/test3", null));
+    }
+
+
+    /**
+     * Tests that {@link DefaultProxySelector} throws a {@link IllegalArgumentException}
+     * for URIs that don't have protocol/scheme information
+     *
+     * @throws Exception
+     */
+    @Test
+    public void testIllegalArgForNoScheme() throws Exception {
+        final ProxySelector selector = new DefaultProxySelector();
+        assertFailsWithIAE(selector, new URI(null, "/test", null));
+    }
+
+    private static void assertFailsWithIAE(final ProxySelector selector, final URI uri) {
+        try {
+            selector.select(uri);
+            Assert.fail("select() was expected to fail for URI " + uri);
+        } catch (IllegalArgumentException iae) {
+            // expected
+        }
+    }
+}