8216988: ServerSocket.implAccept should include warnings about Socket type/state
Reviewed-by: alanb
--- a/src/java.base/share/classes/java/net/ServerSocket.java Fri Jun 07 11:47:49 2019 +0100
+++ b/src/java.base/share/classes/java/net/ServerSocket.java Fri Jun 07 11:51:27 2019 +0100
@@ -472,6 +472,12 @@
* as its arguments to ensure the operation is allowed.
* This could result in a SecurityException.
*
+ * @implNote
+ * An instance of this class using a system-default {@code SocketImpl}
+ * accepts sockets with a {@code SocketImpl} of the same type, regardless
+ * of the {@linkplain Socket#setSocketImplFactory(SocketImplFactory)
+ * client socket implementation factory}, if one has been set.
+ *
* @exception IOException if an I/O error occurs when waiting for a
* connection.
* @exception SecurityException if a security manager exists and its
@@ -501,15 +507,33 @@
/**
* Subclasses of ServerSocket use this method to override accept()
* to return their own subclass of socket. So a FooServerSocket
- * will typically hand this method an <i>empty</i> FooSocket. On
- * return from implAccept the FooSocket will be connected to a client.
+ * will typically hand this method a newly created, unbound, FooSocket.
+ * On return from implAccept the FooSocket will be connected to a client.
+ *
+ * <p> The behavior of this method is unspecified when invoked with a
+ * socket that is not newly created and unbound. Any socket options set
+ * on the given socket prior to invoking this method may or may not be
+ * preserved when the connection is accepted. It may not be possible to
+ * accept a connection when this socket has a {@code SocketImpl} of one
+ * type and the given socket has a {@code SocketImpl} of a completely
+ * different type.
+ *
+ * @implNote
+ * An instance of this class using a system-default {@code SocketImpl}
+ * can accept a connection with a Socket using a {@code SocketImpl} of
+ * the same type: {@code IOException} is thrown if the Socket is using
+ * a custom {@code SocketImpl}. An instance of this class using a
+ * custom {@code SocketImpl} cannot accept a connection with a Socket
+ * using a system-default {@code SocketImpl}.
*
* @param s the Socket
* @throws java.nio.channels.IllegalBlockingModeException
* if this socket has an associated channel,
* and the channel is in non-blocking mode
* @throws IOException if an I/O error occurs when waiting
- * for a connection.
+ * for a connection, or if it is not possible for this socket
+ * to accept a connection with the given socket
+ *
* @since 1.1
* @revised 1.4
* @spec JSR-51