jcertdevtest

A java exercise based on the Sun/Oracle Certified Java Developer assignment. Although I have not yet taken the assignment myself, and that there are many variations of the requirements details, the general requirements and similar examples are available in various exam guide books, online discussion forums etc.

The assignment touches on aspects of IO, networking, concurrency, and designing layered architecture. Swing GUI, and non-coding tasks such as user guide, design discussion etc, are also part of the requirement, but not attempted in this exercise.

Requirements

A room booking system using a custom file datastore.

• GUI client which can:
  1. show all records
  2. search by name/location
  3. book a record with a given customer id (input by user)
• Server to use a provided binary format file datastore
• Server to implement a mandatory interface for CRUD on the file
  • NB: client does NOT make use of all methods in this interface (e.g. client does not need to create/delete/unbook record), but the interface methods must still all be implemented according to the interface descriptions.
• The system can start from a single entry point (same jar file) in 3 different modes (by command line arg):
  1. GUI client (communicate with server over network). Can start multiple.
  2. Server (communicte with clients over network)
  3. Stand-alone (client and server in the same process and NOT going over network. i.e. client calls server logic directly by normal method calls)
• Use either Java RMI or Socket with serialized object for networking.
• Configs are passed in using some GUI on startup (no command arg, config file)

My Changes To Requirements

• Implement an extra mode to run as webapp
  1. instead of Java Swing GUI client, access as a webpage
  2. instead of network server, implement as webapp on Tomcat
• For the network client mode, do not bother with Java Swing, implement a simple CLI client instead.
• Use socket instead of RMI for the network modes. It is quite obvious from exam guides and forum dicussions that RMI should be more appropriate for the given requirements, which also mention it is better to be simple then doing anything complicated for a junior developer to maintain. But socket is more interesting as an exercise.
• For simplicity, takes config from command arg java properties.

Screenshots

Build / Installation

1. Unpack files, go to project root dir.
2. The db file is "db-1x1.db". Take note of its file path which is needed for startup and config.
3. For webapp mode, db file path is set in web.xml. Either first build the .war and then deploy as exploded and modify the xml, or go directly to: /jcertdevtest-webapp/src/main/webapp/WEB-INF/web.xml and change the context param filePath value, before build.
4. From root dir, do mvn clean package
5. For webapp mode, copy created jcertdevtest-webapp.war file to Tomcat webapp dir
6. For other modes, the jar is created in /jcertdevtest-app/target/jcertdevtest-app-1.0-SNAPSHOT.jar

Run

Webapp mode (browser):

http://localhost:{port}/jcertdevtest-webapp/

Network mode server:

java -DfilePath={file path to db file} -Dport={port} jcertdevtest-app-1.0-SNAPSHOT.jar server

Network mode client:

java -Dhost=localhost -Dport={port} jcertdevtest-app-1.0-SNAPSHOT.jar client

Standalone:

java -DfilePath={file path to db file} jcertdevtest-app-1.0-SNAPSHOT.jar standalone

Design

The implemented system has the following modes/layers

1. Webapp mode
   Browser --> HttpServer -> Business -> Database

2. Network mode
   UI --> NetworkClient -> NetworkServer -> Business -> Database

3. Standalone
   UI -> Business -> Database

Main classes:

Common:

• TestApp startup entry point for the network/standalone modes
• CLIClient interactive command line client
• DB mandatory interface
• Data implementation of the mandatory interface
• BookingService interface for the required client functionalities book/search
• BookingServiceImpl implementation with the business logic

Network:

• RemoteBookingServiceClient implementation of BookingService for use on client to call server over network for the actual business implementation
• NetworkClient used by above to help provide a normal blocking method call interface
• NetworkServer Listens for network client connection
• RemoteBookingServiceServerSessionHandler Server side handling per session events talking to the actual BookingService
• NetworkSession used in common on both client and server side to handle a single accepted socket connection, and IO in a non-blocking way (by threads, not NIO).

Web:

• MainServlet handles search and display of the main page
• BookingServlet handles book request from main page