| This interface is used as a heap to control the allocation of sockets.
An instance of this interface can be passed to methods that allocate
sockets. In this way, the actual, underlying type of socket allocated
can be replaced (for instance, with an SSL socket or an firewall-tunnelling
socket), without the user of the socket having to explicitly be aware of
the underlying implementation.
In some ways, this class is a replacement for the
SocketImplFactory class. This class addresses the following
issues.
-
A
SocketImplFactory may be installed only once for the entire
process, so different policies cannot be used concurrently and/or
consectively. For instance, imagine a situation where the user wants one
part of the program talking via SSL to some port on machine A and via
standard sockets to some port on machine B. It is not possible to
install separate SocketImplFactory objects to allow both.
-
The standard
Socket class presumes a highly-connected network
with the ability to resolve hostnames to IP addresses. The standard
Socket class always converts the hostname to an IP address
before calling SocketImplFactory. If the hostname does not
have an IP address, then the SocketImplFactory never gets a
chance to intercept the host name and perform alternate routing based on
the name. For instance, imagine that the user has implemented a
firewall-tunnelling socket; the raw hostname must be passed to the
firewall machine, which allows the socket to be established once some
out-of-band credentials are supplied. But we could never get this far
because the standard Socket class would have already rejected
the request since the IP address of the target machine was unknown.
author:
Colin Stevens (colin.stevens@sun.com)
version:
1.8, 00/03/10 |