Virtual Cafe

This project implements Client-Server Architecture in Java that simulates Cafe operation and is designed to handle multiple client concurrently .

Java Version

JDK 21 is used in this project, so make sure your Java version is up to date if to prevent any error while compiling .

To Check your Java and Java Compiler Version :

javac --version

java --version 

Download latest JDK on Oracle Official Website .

Gson

Note that Gson 2.10.1 is used in this project, so make sure you see a file named "gson-2.10.1.jar" in the root folder befor you run the program .

Download latest Gson on Maven Repository .

Customer Role

Below shows what a customer is able to do from Client Terminal in this program .

Order Drinks
>> order 1 tea
>> order 1 coffee
>> order 1 tea and 2 coffees

Check Order Status
>> order status

Exit Cafe
>> exit

How to Run

Compile Barista.java and Customer.java on terminal .

Windows:
javac -cp .;gson-2.10.1.jar Barista.java
javac Customer.java

Linux: 
javac -cp .:gson-2.10.1.jar Barista.java
javac Customer.java

Everything will be explained based on Windows environment, remember to change ' ; ' to ' : ' in terminal if you are using Linux.

1 . Run the Barista.java (server) and Customer.java (client).

java -cp .;gson-2.10.1.jar Barista
java Customer

2. You will see server is waiting for connection, and a list of Customer Roles displayed in client. Now type your name and request for Order Status in Client Terminal.

>> order status

You should see a message "Oops, no new order found for Your Name"

3. Now repeat the first step and start Customer.java four (4) times in Seperated Terminals. Then, simply enter any name you like in each Client Terminal.

e.g.
>> Liaw Yi Kai

4. Now lets Order Drinks in each Client Terminal, you can type "order status" anytime in any Client Terminal to check their Order Status. Also, observe the Server Terminal and see the Cafe Status, you should be able to see every single change in the Cafe.

1st Client
>> order 10 tea and 10 coffee

2nd Client
>> order 2 teas and 2 coffees

3rd Client
>> order 3 tea

4th Client
>> order 4 coffee

5. Now, before 1st Client's order is delivered, let him exit the Cafe. Either type "exit" or press "CTRL+C". Feel free to play around with it and see the difference later.

>> exit

or 

CTRL + C

6. Now, observe the Server Terminal and you should be able to see message as below. The server checks if 1st Client's orders can be transferred to other 3 customers in the Cafe.

Checking if "1st Client" orders can be transferred..

Removed "1st Client" orders in waiting area Tea(*) Coffee(*)

Finishing "1st Client" orders in brewing area..

7. Then, you should also be able to see message (as below) in Server Terminal regarding order transferred.

(*)Tea (*)Coffee transferred from 1st Client to 2nd Client.

8. You should also see message (as below) in Server Terminal if 1st Client's order in Tray is not fully transferred to other customer. [TRY IT LATER]

(*)Tea removed from 1st Client Tray.

or 

(*)Coffee removed from 1st Client Tray.

9. Don't forget about the Client Terminal too. Other client's orders might be delivered in any seconds! And you should be able to see similar notification (as below) on their terminal screen.

*** NOTIFICATION ***
Dear "2nd Client" your order is delivered (2 teas and 2 coffees)

10. Now, let every client exit and shut down the Server Terminal by "CTRL+C". And you should be able to see a file "serverLog.json" appeared in your root folder. You should see info similar to below in the file.

{
  "2023-11-28 23:44:52:236290800": {
    "clientInCafe": 1,
    "clientWaitingOrder": 0,
    "ordersWaiting": "Tea(0) and Coffee(0)",
    "ordersBrewing": "Tea(0) and Coffee(0)",
    "ordersInTray": "Tea(0) and Coffee(0)",
    "serverMsg": "1st Client entered the Cafe."
  },
  "2023-11-28 23:44:57:845313100": {
    "clientInCafe": 2,
    "clientWaitingOrder": 0,
    "ordersWaiting": "Tea(0) and Coffee(0)",
    "ordersBrewing": "Tea(0) and Coffee(0)",
    "ordersInTray": "Tea(0) and Coffee(0)",
    "serverMsg": "2nd Client entered the Cafe."
  },
  .
  .

~ END ~

Key Highlights (recap)

• Establishes Connection between Client and Server.
• Server handles Multiple Clients Concurrently.
• Server Displays every single Change in the Cafe.
• Client can Place Orders.
• Client can Check Order Status anytime.
• Client can Exit Cafe anytime.
• Client is Automatically Notified when Order is Delivered.
• When client left before order is delivered, server will check and try to Transfer his Orders to Other Clients in the Cafe.
• Server generates Server Log File that records every single change in the Cafe before shutting down.
• Intercepts and handles SIGTERM Signals.

Conclusion

Feel free to play around with the program, obsereve the messages displayed on Client Terminal and Server Terminal on different scenarios. But do note that error checking is not fully implemented in this program, so please at least try to follow the Customer Role, especially when placing orders.

Author

Liaw Yi Kai
University Of Essex
yl23705@essex.ac.uk

Updated November, 2023.