Java Reference
In-Depth Information
The GCF hierarchy is a tightly woven collection of interfaces with a sprinkling of classes:
•
The
Connector
class
: Responsible for operating as a factory of
Connection
objects.
•
The
Connection
interface
: Represents a generic connection between two entities.
The
Connection
interface defines the
close
method, which is responsible for closing
a connection.
•
The
DatagramConnection
interface
: Defines the actions you can take on a datagram-
oriented connection such as UDP.
•
The
StreamConnection
interface
: Defines the actions you can take on a stream-
oriented connection such as TCP.
StreamConnection
instances are bidirectional,
consisting of an
InputConnection
(from which you read data) and an
OutputConnection
(to which you write data).
•
The
StreamConnectionNotifier
interface
: Defines the actions you can take when
listening for a new
StreamConnection
.
•
The
ContentConnection
interface
: Supports the passing of content encoded through
a well-known codec.
•
The
Datagram
interface
: Defines an abstract interface for a single datagram.
Datagram
s are bidirectional, implementing this functionality by extending the
DataInput
and
DataOutput
interfaces.
•
The
IOException
class
: Signals generic communications errors such as network fail-
ures, and the
ConnectionNotFoundException
, which is thrown by
Connector
class
methods when you attempt to create a connection that the platform cannot
resolve. (This
IOException
class isn't formally part of the GCF.)
When you use the GCF, you follow these steps:
1.
Create a URL describing the kind of socket you'd like to open and detailing the
address and name of the resource to which you want to connect.
2.
Invoke the
Connector.open
class method, passing the URL you constructed to
receive an instance of a specific
Connection
subclass.
3.
Use the concrete
Connection
subclass methods for the kind of connection
Connector.open
returned to you to work with the connection.
The pseudocode in Listing 12-1 demonstrates this pattern, opening an HTTP con-
nection to the server
www.nowhere.com
and obtaining an
InputStream
from which to read.
