8238231: Custom DatagramSocketImpl's create method not called when with protected constructor

Allow the socket to be lazily created if not created by the constructor.

Reviewed-by: alanb

src/java.base/share/classes/java/net/DatagramSocket.java

@@ -118,7 +118,8 @@ public class DatagramSocket implements java.io.Closeable {
      */
     private boolean bound = false;
     private boolean closed = false;
-    private Object closeLock = new Object();
+    private volatile boolean created;
+    private final Object closeLock = new Object();
 
     /*
      * The implementation of this DatagramSocket.
@@ -292,6 +293,9 @@ public class DatagramSocket implements java.io.Closeable {
         // create a datagram socket.
         boolean multicast = (this instanceof MulticastSocket);
         this.impl = createImpl(multicast);
+        // creates the udp socket
+        impl.create();
+        created = true;
         this.oldImpl = checkOldImpl(impl);
         if (bindaddr != null) {
             try {
@@ -392,20 +396,27 @@ public class DatagramSocket implements java.io.Closeable {
         } else {
             impl = DefaultDatagramSocketImplFactory.createDatagramSocketImpl(multicast);
         }
-        // creates a udp socket
-        impl.create();
         return impl;
     }
 
     /**
-     * Return the {@code DatagramSocketImpl} attached to this socket.
+     * Return the {@code DatagramSocketImpl} attached to this socket,
+     * creating the socket if not already created.
      *
      * @return  the {@code DatagramSocketImpl} attached to that
      *          DatagramSocket
-     * @throws SocketException never thrown
+     * @throws SocketException if creating the socket fails
      * @since 1.4
      */
-    DatagramSocketImpl getImpl() throws SocketException {
+    final DatagramSocketImpl getImpl() throws SocketException {
+        if (!created) {
+            synchronized (this) {
+                if (!created)  {
+                    impl.create();
+                    created = true;
+                }
+            }
+        }
         return impl;
     }
 

test/jdk/java/net/DatagramSocket/SetReceiveBufferSize.java

@@ -30,19 +30,17 @@ import java.net.*;
 
 public class SetReceiveBufferSize {
 
-  public static void main(String args[]) throws Exception {
-    boolean error = true;
-     DatagramSocket soc = null;
+    public static void main(String args[]) throws Exception {
+        boolean error = true;
 
-     try {
-       soc = new DatagramSocket();
-       soc.setReceiveBufferSize(0);
-     } catch(IllegalArgumentException e) {
-       error = false;
-     }
+        try (DatagramSocket soc = new DatagramSocket()) {
+            soc.setReceiveBufferSize(0);
+        } catch (IllegalArgumentException e) {
+            error = false;
+        }
 
-     if (error) {
-       throw new RuntimeException("Test with 0 buffer size failed!");
-     }
-  }
+        if (error) {
+            throw new RuntimeException("Test with 0 buffer size failed!");
+        }
+    }
 }

test/jdk/java/net/DatagramSocketImpl/TestCreate.java

@@ -0,0 +1,120 @@
+/*
+ * Copyright (c) 2020, 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.
+ */
+
+/*
+ * @test
+ * @bug 8238231
+ * @summary test that DatagramSocket calls java.net.DatagramSocketImpl::create
+ * @run testng/othervm TestCreate
+ */
+
+import org.testng.annotations.Test;
+
+import java.io.IOException;
+import java.net.DatagramPacket;
+import java.net.DatagramSocket;
+import java.net.DatagramSocketImpl;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.MulticastSocket;
+import java.net.NetworkInterface;
+import java.net.SocketAddress;
+import java.net.SocketOption;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.atomic.AtomicBoolean;
+import static org.testng.Assert.assertTrue;
+
+public class TestCreate {
+
+    @Test
+    public void datagramSocketImpl() throws IOException {
+        CustomDatagramSocketImpl dsi = new CustomDatagramSocketImpl();
+        CustomDatagramSocket ds = new CustomDatagramSocket(dsi);
+        ds.bind(new InetSocketAddress(0));
+        assertTrue(dsi.created.get(), "new CustomDatagramSocket(dsi)");
+
+        CustomDatagramSocketImpl dsi2 = new CustomDatagramSocketImpl();
+        CustomDatagramSocketImpl dsi3 = new CustomDatagramSocketImpl();
+        Iterator<CustomDatagramSocketImpl> iterator = List.of(dsi2, dsi3).iterator();
+        DatagramSocket.setDatagramSocketImplFactory(() -> iterator.next());
+
+        DatagramSocket ds2 = new DatagramSocket();
+        assertTrue(dsi2.created.get(), "new DatagramSocket()");
+
+        MulticastSocket ds3 = new MulticastSocket();
+        assertTrue(dsi3.created.get(), "new MulticastSocket()");
+    }
+
+    static class CustomDatagramSocket extends DatagramSocket {
+        CustomDatagramSocket(DatagramSocketImpl impl) {
+            super(impl);
+        }
+    }
+
+    // A DatagramSocketImpl that delegates the three new-style socket option
+    // methods to the default java.net.DatagramSocketImpl implementation.
+    static class CustomDatagramSocketImpl extends DatagramSocketImpl {
+
+        final AtomicBoolean created = new AtomicBoolean(false);
+
+        @Override
+        public <T> void setOption(SocketOption<T> name, T value) throws IOException {
+            super.setOption(name, value);
+        }
+
+        @Override
+        public Set<SocketOption<?>> supportedOptions() {
+            return super.supportedOptions();
+        }
+
+        @Override
+        public <T> T getOption(SocketOption<T> name) throws IOException {
+            return super.getOption(name);
+        }
+
+        // --
+        @Override protected void create() {
+            if (created.compareAndExchange(false, true)) {
+                throw new AssertionError("create called twice");
+            }
+        }
+        @Override protected void bind(int lport, InetAddress laddr) { }
+        @Override protected void send(DatagramPacket p) { }
+        @Override protected int peek(InetAddress i) { return 0; }
+        @Override protected int peekData(DatagramPacket p) { return 0; }
+        @Override protected void receive(DatagramPacket p) { }
+        @Override protected void setTTL(byte ttl) { }
+        @Override protected byte getTTL() { return 0; }
+        @Override protected void setTimeToLive(int ttl) { }
+        @Override protected int getTimeToLive() { return 0; }
+        @Override protected void join(InetAddress inetaddr) { }
+        @Override protected void leave(InetAddress inetaddr)  { }
+        @Override protected void joinGroup(SocketAddress mcastaddr, NetworkInterface netIf) { }
+        @Override protected void leaveGroup(SocketAddress mcastaddr, NetworkInterface netIf) { }
+        @Override protected void close() { }
+        @Override public void setOption(int optID, Object value) { }
+        @Override public Object getOption(int optID) { return null; }
+    }
+}