Chat CRC Cards

Here is an intial set of CRC cards for the Chat system.

Client

Class

ChatApplet

Responsibility

1. To handle the text typed by a single client (person) and send it to the server.

Collaborators

A text field for entry

A button to send the text field

An action listener (Sender) to handle the button.

2. To capture the text returned by the server and display it to the client.

Collaborators

A text area for display

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Class

Sender

Responsibility

1. To send the text field to the server when the user hits the button or the enter key

Collaborators

The text field

The Button

The server.

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Server

Class

ChatServer

Responsibility

1. Sets up the ServerSocket and listens for connects

2. Creates and starts the Echoer

Collaborators

Echoer

3. Creates a Buffer.

Collaborators

Buffer

4. Creates ChatHandlers as needed.

Collaborators

ChatHandler

5. Maintains an array or list of connected clients.

 

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Class

ChatHandler

Responsibility

1. Accepts input from the client and puts it into the buffer

Collaborators

Buffer

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Class

Buffer

Responsibility

1. Synchronizes (linearizes) puts from various ChatHandlers. Implements a one element queue.

Collaborators

Echoer

ChatHandler

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Class

Echoer

Responsibility

1. Runs in a thread that polls the buffer for strings. When one appears it sends it to all clients.

Collaborators

The ChatServer (its client list).

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Last Updated: September 14, 2001