uk.ac.sheffield.vtts.client.pojo

Class Account

java.lang.Object

uk.ac.sheffield.vtts.client.pojo.Account

public class Account
extends java.lang.Object

Account is a correct POJO implementation of the Account.xml specification. This uses the State Pattern (a Design Pattern from Gamma, et al.) for its implementation. All requests are delegated to an abstract State, which has concrete subclasses Closed and Open, which respond to certain requests and ignore others. This is a good implementation strategy to ensure that no information is returned by a service, when it is in an inappropriate state.

Otherwise, the account holder is recorded in a field when the Account is opened; and the balance is recorded in another field, when amounts are deposited or withdrawn. This implementation obeys the preconditions in the specification, which treat any attempt to deposit or withdraw a zero or negative amount as an error. Errors are treated in this example as normal responses, in which bad requests have no effect, but return signal Boolean results to indicate success or failure.

Suggestions are given for how to modify the source code to seed faults deliberately, which will be detected during testing.

Version:

1.0

Author:

Anthony J H Simons

Constructor Summary

Constructors

Constructor and Description
Account() Creates this Account.

Method Summary

Methods

Modifier and Type	Method and Description
java.lang.Boolean	close() Attempts to close this Account.
java.lang.Boolean	deposit(int amount) Attempts to deposit an amount in this Account.
java.lang.Integer	getBalance() Attempts to inspect the current balance.
java.lang.String	getHolder() Attempts to inspect the current holder.
java.lang.String	getScenario() Returns the last scenario that was enacted.
java.lang.String	getState() Returns the last state that was entered.
java.lang.Boolean	open(java.lang.String holder) Attempts to open this Account for a given holder.
java.lang.Boolean	withdraw(int amount) Attempts to withdraw an amount from this Account.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Account

public Account()

Creates this Account. Enacts the scenario create/ok. Sets the holder to null and the balance to zero. For POJO implementations, the constructor is also used to reset the service.

Method Detail

getScenario

public java.lang.String getScenario()

Returns the last scenario that was enacted. This State Pattern implementation logs separately the request received and the response triggered (which is state-dependent). The name of the last scenario that was enacted is obtained by concatenating the request, "/" and the response.

Returns:

the last scenario that was enacted.

getState

public java.lang.String getState()

Returns the last state that was entered. This State Pattern implementation models the states explicitly as nested inner classes, which also have access to the Account's fields. The name of the current state is obtained by reflection on the class name.

Returns:

the name of the current State instance.

open

public java.lang.Boolean open(java.lang.String holder)

Attempts to open this Account for a given holder. If this account is already open, enacts the scenario open/ignore. If this account is closed and the holder is non-empty, enacts the scenario open/ok and enters the Open state. Otherwise, enacts the scenario open/error and remains in the Closed state.

Parameters:

holder - the account holder.

Returns:

true, if open succeeded, false if it failed, or null if it was ignored.

close

public java.lang.Boolean close()

Attempts to close this Account. If the account is Closed, enacts the scenario close/ignore. If the account is Open and the balance is zero, enacts the scenario close/ok and enters the Closed state. If the account is Open but the balance is not zero, enacts the scenario close/error and remains in the Open state.

Returns:

true, if closing succeeded, false if it failed, or null if it was ignored.

deposit

public java.lang.Boolean deposit(int amount)

Attempts to deposit an amount in this Account. If the account is Closed, enacts deposit/ignore. If the account is Open but the amount is not positive, enacts deposit/error; otherwise enacts deposit/ok and adds the amount to the balance.

Parameters:

amount - the amount to deposit.

Returns:

true, if deposit succeeded, false if it failed, or null if it was ignored.

withdraw

public java.lang.Boolean withdraw(int amount)

Attempts to withdraw an amount from this Account. If the account is Closed, enacts withdraw/ignore. If the account is Open but the amount is not positive, enacts withdraw/error. If the account is Open but the positive amount is greater than the current balance, enacts withdraw/blocked. Otherwise, the positive amount is less than or equal to the current balance, so enacts withdraw/ok and subtracts the amount from the balance.

Parameters:

amount - the amount to withdraw.

Returns:

true, if withdraw succeeded, false if it failed, or null if it was ignored.

getBalance

public java.lang.Integer getBalance()

Attempts to inspect the current balance. If the account is Closed, enacts inspect/ignore. If the account is Open, enacts inspect/ok and returns the current balance.

Returns:

the current balance, if inspect succeeded, or null if it was ignored.

getHolder

public java.lang.String getHolder()

Attempts to inspect the current holder. If the account is Closed, enacts inspect/ignore. If the account is Open, enacts inspect/ok and returns the current balance.

Returns:

the current balance, if inspect succeeded, or null if it was ignored.