Appendix A
iBank Application specification
The sample application we defined is called 'iBank' and simulates a basic online banking service with the following functionality:
- log on to the online banking service
- view/edit personal details and branch details
- summary view of accounts showing cleared balances
- facility to drill down by account to view individual transaction history
- money transfer service, allowing online transfer of funds between accounts
- compound interest earnings projection over a number of years for a given principal and annual yield rate.
The application is designed after the MVC (Model-View-Controller) model where:
- EJBs are used to define the business and data model components of the application
- Java Server Pages handle the presentation logic and represent the View.
- Servlets play the role of Controllers and handle application logic, taking charge of calling the business logic components and accessing business data via EJBs (the Model), and dispatching processed data for display to Java Server Pages (the View).
For packaging and deployment of application components, standard J2EE methods are used, and include definition of deployment descriptors, and packaging of application components within archive files:
- a WAR archive file for the Web application including HTML pages, images, Servlets, JSPs and custom tag libraries, and ancillary server-side Java classes.
- EJB-JAR archive files for the packaging of one or more EJBs, including deployment descriptor, bean class and interfaces, stub and skeleton classes, and other helper classes as required.
- an EAR archive file for the packaging of the enterprise application module that includes the Web application module and the EJB modules used by the application.
The use of standard J2EE packaging methods will be useful in pointing out any differences between Sun™ ONE Application Server 6.0/6.5 and Sun ONE Application Server 7, and any issues arising thereof.
Tools used for the development of the application
Sun ONE Studio Enterprise Edition for Java, Release 4.0
As Sun ONE Application Server 7 supports both the EJB 1.0 and EJB 1.1 standard, the other EJBs in the iBank application (2 session EJBs and the BMP entity bean) were developed with Sun ONE Studio for Java, and then packaged and deployed in Sun ONE Application Server 7 using the supplied Application Assembly Tool. This approach enabled us to test usage of a third-party IDE for developing 1.1 EJBs in Sun ONE Application Server 7. Moreover, the approach also gave us the chance to experiment with migrating 1.1 EJBs developed for Sun ONE Application Server 6.5 to Sun ONE Application Server 7.
The Sun ONE Studio for Java development environment was also used to migrate EJB components in the iBank application to Sun ONE Application Server (code adapted from EJB 1.0 standard to EJB 1.1, O/R mapping for CMP entity beans, configuration of deployment properties and packaging of the application's different modules).
Oracle 8i 8.1.6
The database was developed with Oracle 8i (version 8.1.6) and the JDBC driver used to access the database was the thin Oracle driver (type 4).
Database schema
- The iBank database schema is derived from the following business rules:
- The iBank company has local Branches in major cities
- A Branch manages all customers within its regional area.
- A Customer has one or more accounts held at their regional branch.
- A customer Account is uniquely identified by the branch code and account no., and also holds the no. of the customer to which it belongs. The current cleared balance available is also stored with the account.
- Accounts are of a particular Account Type that is used to distinguish between several kinds of accounts (checking account, savings account, etc.)
- Each Account Type stores a number of particulars that apply to all accounts of this type (regardless of branch or customer) such as interest rate and allowed overdraft limit.
- Every time a customer receives or pays money into/from one of their accounts, the transaction is recorded in a global transaction log, the Transaction History.
- The Transaction History stores details about individual transactions, such as the relevant branch code and account no., the date the transaction was posted (recorded), a code identifying the type of transaction and a complementary description of the particular transaction, and the amount for the transaction.
- Transaction types allow different types of transactions to be distinguished, such as cash deposit, credit card payment, fund transfer between accounts, and so on.
These business rules are illustrated in the entity-relationship diagram below:
Figure A-1 Database Schema
The database model translates as the series of table definitions below, where primary key columns are printed in bold type, while foreign key columns are shown in italics.
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BRANCH
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BRANCH_CODE
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CHAR(4)
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NOT NULL
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4-digit code identifying the branch
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BRANCH_NAME
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VARCHAR(40)
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NOT NULL
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Name of the branch
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BRANCH_ADDRESS1
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VARCHAR(60)
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NOT NULL
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Branch postal address, street address, 1st line
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BRANCH_ADDRESS2
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VARCHAR(60)
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Branch postal address, street address, 2nd line
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BRANCH_CITY
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VARCHAR(30)
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NOT NULL
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Branch postal address, City
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BRANCH_ZIP
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VARCHAR(10)
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NOT NULL
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Branch postal address, Zip code
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BRANCH_STATE
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CHAR(2)
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NOT NULL
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Branch postal address, State abbreviation
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CUSTOMER
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CUST_NO
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INT
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NOT NULL
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iBank customer number (global)
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BRANCH_CODE
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CHAR(4)
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NOT NULL
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References this customer's branch
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CUST_USERNAME
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VARCHAR(16)
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NOT NULL
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Customer's login username
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CUST_PASSWORD
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VARCHAR(10)
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NOT NULL
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Customer's login password
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CUST_EMAIL
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VARCHAR(40)
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Customer's e-mail address
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CUST_TITLE
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VARCHAR(3)
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NOT NULL
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Customer's courtesy title
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CUST_GIVENNAMES
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VARCHAR(40)
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NOT NULL
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Customer's given names
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CUST_SURNAME
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VARCHAR(40)
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NOT NULL
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Customer's family name
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CUST_ADDRESS1
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VARCHAR(60)
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NOT NULL
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Customer postal address, street address, 1st line
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CUST_ADDRESS2
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VARCHAR(60)
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Customer postal address, street address, 2nd line
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CUST_CITY
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VARCHAR(30)
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NOT NULL
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Customer postal address, City
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CUST_ZIP
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VARCHAR(10)
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NOT NULL
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Customer postal address, Zip code
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CUST_STATE
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CHAR(2)
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NOT NULL
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Customer postal address, State abbreviation
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ACCOUNT_TYPE
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ACCTYPE_ID
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CHAR(3)
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NOT NULL
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3-letter account type code
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ACCTYPE_DESC
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VARCHAR(30)
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NOT NULL
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Account type description
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ACCTYPE_INTERESTRATE
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DECIMAL(4,2)
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DEFAULT 0.0
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Annual interest rate
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ACCOUNT
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BRANCH_CODE
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CHAR(4)
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NOT NULL
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branch code (primary-key part 1)
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ACC_NO
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CHAR(8)
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NOT NULL
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account no. (primary-key part 2)
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CUST_NO
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INT
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NOT NULL
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Customer to whom accounts belongs
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ACCTYPE_ID
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CHAR(3)
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NOT NULL
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Account type, references ACCOUNT_TYPE
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ACC_BALANCE
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DECIMAL(10,2)
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DEFAULT 0.0
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Cleared balance available
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TRANSACTION_TYPE
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TRANSTYPE_ID
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CHAR(4)
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NOT NULL
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A 4-letter transaction type code
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TRANSTYPE_DESC
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VARCHAR(40)
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NOT NULL
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Human-readable description of code
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TRANSACTION_HISTORY
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TRANS_ID
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LONGINT
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NOT NULL
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Global transaction serial no
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BRANCH_CODE
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CHAR(4)
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NOT NULL
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key referencing ACCOUNT part 1
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ACC_NO
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CHAR(8)
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NOT NULL
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key referencing ACCOUNT part 2
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TRANSTYPE_ID
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CHAR(4)
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NOT NULL
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References TRANSACTION_TYPE
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TRANS_POSTDATE
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TIMESTAMP
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NOT NULL
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Date & time transaction was posted
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TRANS_DESC
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VARCHAR(40)
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Additional details for the transaction
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TRANS_AMOUNT
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DECIMAL(10,2)
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NOT NULL
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Money amount for this transaction
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Application navigation and logic
High-level view of application navigation
Detailed application logic
Application Components
Each table in the database schema is encapsulated as an entity bean:
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Entity Bean
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Database Table
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Account
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ACCOUNT table
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AccountType
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ACCOUNT_TYPE table
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Branch
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BRANCH table
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Customer
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CUSTOMER table
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Transaction
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TRANSACTION_HISTORY table
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TransactionType
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TRANSACTION_TYPE table
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All entity beans use container-managed persistence (CMP), except Customer, which uses bean-managed persistence (BMP).
Currently, the application only makes use of the Account, AccountType, Branch, and Customer beans.
Business components of the application are encapsulated by session beans-
The BankTeller bean is a stateful session bean that encapsulates all interaction between the customer and the system. BankTeller is notably in charge of:
- authenticating a customer through the authCheck() method
- giving the list of accounts for the customer through the getAccountSummary() method
- transferring funds between accounts on behalf of the customer through the transferFunds() method.
The InterestCalculator bean is a stateless session bean that encapsulates financial calculations. It is responsible for providing the compound interest projection calculations, through the projectEarnings() method.
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Component name
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Purpose
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LoginServlet
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Authenticates the user with the BankTeller session bean (authCheck() method), creates the HTTP session and saves information pertaining to the user in the session.Upon successful authentication, forwards request to the main menu page (UserMenu.jsp)
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CustomerProfileServlet
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Retrieves customer and branch details from the Customer and Branch entity beans and forwards request to the view/edit details page (CustomerProfile.jsp)
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UpdateCustomerDetailsServlet
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Attempts to effect customer details changes amended in CustomerProfile.jsp by updating the Customer entity bean after checking validity of changes.Redirects to UpdatedDetails.jsp if success, or to DetailsUpdateFailed.jsp in case of incorrect input.
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ShowAccountSummaryServlet
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Retrieves the list of customer accounts from the BankTeller session bean (getAccountSummary() method) and forwards request to AccountSummary.jsp for display
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TransferFundsServlet
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Retrieves the list of customer accounts from the BankTeller session bean (getAccountSummary() method) and forwards request to TransferFunds.jsp allowing the user to set up the transfer operation.
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CheckTransferServlet
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Checks the validity of source and destination accounts selected by the user for transfer and the amount entered. Calls the transferFunds() method of the BankTeller session bean to perform the transfer operation. Redirects the user to CheckTransferFailed.jsp in case of input error or processing error, or to TransferSuccess.jsp if the operation was successfully carried out
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ProjectEarningsServlet
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Retrieves the interest calculation parameters defined by the user in InterestCalc.jsp and calls the projectEarnings() method of the InterestCalculator stateless session bean to perform the calculation, and forwards results to the ShowProjectionResults.jsp page for display. In case of invalid input, redirects to BadIntCalcInput.jsp
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Component name
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Purpose
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index.jsp
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Index page to the application that also serves as the login page.
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LoginError.jsp
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Login error page displayed in case of invalid user credentials supplied. Prints an indication as to why login was unsuccessful.
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Header.jsp
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Page header that is dynamically included in every HTML page of the application
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CheckSession.jsp
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This page is statically included in every page in the application and serves to verify whether the user is logged in (i.e. has a valid HTTP session). If no valid session is active, the user is redirected to the NotLoggedIn.jsp page
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NotLoggedIn.jsp
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Page that the user gets redirected to when they try to access an application page without having gone through the login process first.
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UserMenu.jsp
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Main application menu page that the user gets redirected to after successfully logging in. This page provides links to all available actions.
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CustomerProfile.jsp
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Page displaying editable customer details and static branch details. This page allows the customer to amend their correspondence address
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UpdatedDetails.jsp
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Page where the user gets redirected to after successfully updating their details.
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DetailsUpdateFailed.jsp
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Page where the user gets redirected if an input error prevents their details to be updated.
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AccountSummaryPage.jsp
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This page displays the list of accounts belonging to the customer in tabular form listing the account no, account type and current balance. Clicking on an account no. in the table causes the application to present a detailed transaction history for the selected account
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ShowTransactionHistory.jsp
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This page prints the detailed transaction history for a particular account no. The transaction history is printed using a custom tag library.
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TransferFunds.jsp
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This page allows the user to set up a transfer from one account to another for a specific amount of money.
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TransferCheckFailed.jsp
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When the user chooses incorrect settings for fund transfer, they get redirected to this page.
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TransferSuccess.jsp
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When the fund transfer set-up by the user can successfully be carried out, this page will be displayed, showing a confirmation message.
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InterestCalc.jsp
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This page allows the user to enter parameters for a compound interest calculation.
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BadIntCalcInput.jsp
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If the parameters for compound interest calculation are incorrect, the user gets redirected to this page.
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ShowProjectionResults.jsp
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When an interest calculation is successfully carried out, the user is redirected to this page that displays the projection results in tabular form.
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Logout.jsp
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Exit page of the application. This page removes the stateful session bean associated with the user and invalidates the HTTP session.
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Error.jsp
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In case of unexpected application error, the user will be redirected to this page that will print details about the exception that occurred.
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Fitness of design choices with regard to potential migration issues
While many of application design choices made are certainly debatable especially in a "real-world" context, care was taken to ensure that these choices enabled the sample application to encompass as many potential issues as possible as one would face in the process of migrating a typical J2EE application.
This section will go through the potential issues that one can face when migrating a J2EE application, and the corresponding component of iBank that was included to check for this issue during the migration process:-
With respect to the selected migration areas to address, the white paper specifically looks at the following technologies:
Servlets
- iBank includes a number of servlets, that enable us to detect potential issues with:
- The use of generic functionality of the Servlet API.
- Storage/retrieval of attributes in the HTTP session and HTTP request.
- Retrieval of servlet context initialisation parameters.
- Page redirection.
Java Server Pages
With respect to the JSP specification, the following aspects have been addressed:
- Use of JSP declarations, scriptlets, expressions, and comments.
- Static includes (<%@ include file="…" %>): notably tested with the inclusion of the CheckSession.jsp file in every page).
- Dynamic includes (<jsp:include page=… />): this is catered for by the dynamic inclusion of Header.jsp in every page.
- Use of custom tag libraries: a custom tag library is used in ShowTransactionHistory.jsp.
- Error pages for JSP exception handling: the Error.jsp page is the application error redirection page.
JDBC
The iBank application accesses a database via a connection pool and data source, both programmatically (BMP entity bean, BankTeller session bean, custom tag library) and declaratively (with the CMP entity beans).
Enterprise Java Beans
iBank uses a variety of Enterprise Java Beans:
Entity beans:
Bean-managed persistance ("Customer" bean): that allows us to test:
- JNDI lookup of initial context
- pooled data source access via JDBC
- definition of a BMP custom finder ("findByCustUsername()")
- Object/Relational mapping with the development tool and within the deployment descriptor
- Use of composite primary keys ("Account")
- Definition of custom CMP finders (with the "Account" bean, and its "findOrderedAccountsForCustomer()" method). This is the occasion to look at differences in declaring the query logic in the deployment descriptor, and also to have a complex example returning a collection of objects.
- using and deploying a stateless session bean
- calling a business method for calculations
- looking up various interfaces using JNDI and initial contexts
- using JDBC to perform database queries
- using various transactional attributes on bean methods
- using container-demarcated transactions
- maintaining conversational state between calls
- business methods acting as front-ends to entity beans (e.g., the "getAccountSummary()" method)
Application Packaging
iBank is packaged following J2EE standard procedures, using:-
- a Web application archive file for the Web application module, and EJB-JAR archives for EJBs.
- an Enterprise application archive file (EAR file) for the final packaging of the Web application and EJB modules.
