Summary

This CSR proposes to deprecate the API points for statically configuring a system-wide factory for the socket types in the java.net package.

Specifically, the following methods:

• static void ServerSocket.setSocketFactory​(SocketImplFactory fac)
• static void Socket.setSocketImplFactory​(SocketImplFactory fac)
• static void DatagramSocket.setDatagramSocketImplFactory​(DatagramSocketImplFactory fac)

Problem

In early JDK releases, these methods provided a way to replace the system wide implementation of Socket, ServerSocket, and DatagramSocket. However, they have been mostly obsolete since Java 1.4.

Solution

If required, a Socket, or ServerSocket, can be created to use a custom implementation by extending their corresponding class and using the protected constructor Socket(SocketImpl), or ServerSocket(SocketImpl), that takes a SocketImpl implementation as a parameter. The constructor DatagramSocket(DatagramSocketImpl) can also be used in similar way for the creation of a DatagramSocket with a custom implementation.

Alternatively, SocketChannel, ServerSocketChannel, or DatagramChannel can be used.

Specification

java/net/Socket.java

    /**
     * Sets the client socket implementation factory for the
     * application. The factory can be specified only once.
     * <p>
     * When an application creates a new client socket, the socket
     * implementation factory's {@code createSocketImpl} method is
     * called to create the actual socket implementation.
     * <p>
     * Passing {@code null} to the method is a no-op unless the factory
     * was already set.
     * <p>If there is a security manager, this method first calls
     * the security manager's {@code checkSetFactory} method
     * to ensure the operation is allowed.
     * This could result in a SecurityException.
     *
     * @param      fac   the desired factory.
     * @throws     IOException  if an I/O error occurs when setting the
     *               socket factory.
     * @throws     SocketException  if the factory is already defined.
     * @throws     SecurityException  if a security manager exists and its
     *             {@code checkSetFactory} method doesn't allow the operation.
     * @see        java.net.SocketImplFactory#createSocketImpl()
     * @see        SecurityManager#checkSetFactory
 +   * @deprecated Use a {@link javax.net.SocketFactory} and subclass {@code Socket}
 +   *    directly.
 +   *    <br> This method provided a way in early JDK releases to replace the
 +   *    system wide implementation of {@code Socket}. It has been mostly
 +   *    obsolete since Java 1.4. If required, a {@code Socket} can be
 +   *    created to use a custom implementation by extending {@code Socket}
 +   *    and using the {@linkplain #Socket(SocketImpl) protected
 +   *    constructor} that takes an {@linkplain SocketImpl implementation}
 +   *    as a parameter.
     */
 +  @Deprecated(since = "17")
    public static synchronized void setSocketImplFactory(SocketImplFactory fac)

java/net/ServerSocket.java

    /**
     * Sets the server socket implementation factory for the
     * application. The factory can be specified only once.
     * <p>
     * When an application creates a new server socket, the socket
     * implementation factory's {@code createSocketImpl} method is
     * called to create the actual socket implementation.
     * <p>
     * Passing {@code null} to the method is a no-op unless the factory
     * was already set.
     * <p>
     * If there is a security manager, this method first calls
     * the security manager's {@code checkSetFactory} method
     * to ensure the operation is allowed.
     * This could result in a SecurityException.
     *
     * @param      fac   the desired factory.
     * @throws     IOException  if an I/O error occurs when setting the
     *               socket factory.
     * @throws     SocketException  if the factory has already been defined.
     * @throws     SecurityException  if a security manager exists and its
     *             {@code checkSetFactory} method doesn't allow the operation.
     * @see        java.net.SocketImplFactory#createSocketImpl()
     * @see        SecurityManager#checkSetFactory
 +   * @deprecated Use a {@link javax.net.ServerSocketFactory} and subclass {@code ServerSocket}
 +   *    directly.
 +   *    <br> This method provided a way in early JDK releases to replace the
 +   *    system wide implementation of {@code ServerSocket}. It has been mostly
 +   *    obsolete since Java 1.4. If required, a {@code ServerSocket} can be
 +   *    created to use a custom implementation by extending {@code ServerSocket}
 +   *    and using the {@linkplain #ServerSocket(SocketImpl) protected
 +   *    constructor} that takes an {@linkplain SocketImpl implementation}
 +   *    as a parameter.
     */
 +  @Deprecated(since = "17")
    public static synchronized void setSocketFactory(SocketImplFactory fac) throws IOException {

java/net/DatagramSocket.java

    /**
     * Sets the datagram socket implementation factory for the
     * application. The factory can be specified only once.
     * <p>
     * When an application creates a new datagram socket, the socket
     * implementation factory's {@code createDatagramSocketImpl} method is
     * called to create the actual datagram socket implementation.
     * <p>
     * Passing {@code null} to the method is a no-op unless the factory
     * was already set.
     *
     * <p>If there is a security manager, this method first calls
     * the security manager's {@code checkSetFactory} method
     * to ensure the operation is allowed.
     * This could result in a SecurityException.
     *
     * @param      fac   the desired factory.
     * @throws     IOException  if an I/O error occurs when setting the
     *              datagram socket factory.
     * @throws     SocketException  if the factory is already defined.
     * @throws     SecurityException  if a security manager exists and its
     *             {@code checkSetFactory} method doesn't allow the operation.
     * @see       java.net.DatagramSocketImplFactory#createDatagramSocketImpl()
     * @see       SecurityManager#checkSetFactory
     * @since 1.3
     *
 +   * @deprecated Use {@link DatagramChannel}, or subclass {@code DatagramSocket}
 +   *    directly.
 +   *    <br> This method provided a way in early JDK releases to replace the
 +   *    system wide implementation of {@code DatagramSocket}. It has been mostly
 +   *    obsolete since Java 1.4. If required, a {@code DatagramSocket} can be
 +   *    created to use a custom implementation by extending {@code DatagramSocket}
 +   *    and using the {@linkplain #DatagramSocket(DatagramSocketImpl) protected
 +   *    constructor} that takes an {@linkplain DatagramSocketImpl implementation}
 +   *    as a parameter.
     */
 +  @Deprecated(since = "17")
    public static synchronized void setDatagramSocketImplFactory(DatagramSocketImplFactory fac) throws IOException