figure 10-1, model transformations, refactorings, forward engineering, and reverse engineering

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 1

Figure 10-1, Model transformations, refactorings, forward engineering, and reverse engineering.

Source code spaceModel space

Modeltransformation

RefactoringForward engineering

Reverse engineering

Figure 10-2, An example of an object model transformation.

Player

Object design model before transformation

Object design model after transformation

AdvertiserLeagueOwner

+email:Address

Advertiser

+email:Address

Player

+email:Address

LeagueOwner

+email:Address

Figure 10-3, Applying the Pull Up Field refactoring.

Before refactoring

public class Player {private String email;//...

}public class LeagueOwner {

private String eMail;//...

}public class Advertiser {

private String email_address;//...

After refactoringpublic class User {

private String email;}public class Player extends User {

//...}public class LeagueOwner extends

User {//...

}public class Advertiser extends

User {//...

Figure 10-4, Pull Up Constructor Body refactoring.Before refactoring

public class User {private String email;

public class Player extends User {public Player(String email) {

this.email = email;}

}public class LeagueOwner extends

User{public LeagueOwner(String email) {

}public class Advertiser extends User{

public Advertiser(String email) {this.email = email;

After refactoring

public class User {public User(String email) {

}public class Player extends User {

public Player(String email) {super(email);

}}public class LeagueOwner extends User

{public LeagueOwner(String email) {

super(email);}

}public class Advertiser extends User {

public Advertiser(String email) {super(email);

Figure 10-5, Realization of User and LeagueOwner

public class User {private String email;public String getEmail() {

return email;}public void setEmail(String value){

email = value;}public void notify(String msg) {

// ....}/* Other methods omitted */

public class LeagueOwner extends User {

private int maxNumLeagues;

public int getMaxNumLeagues() {

return maxNumLeagues;

public void setMaxNumLeagues

(int value) {

maxNumLeagues = value;

/* Other methods omitted */

User LeagueOwner

+maxNumLeagues:int

Source code after transformation

+email:String+notify(msg:String)

Figure 10-6, Collapsing an object without interesting behavior into an attribute

Person SocialSecurity

number:String

Person

SSN:String

Figure 10-7, Delaying expensive computations

filename:String

paint()

filename:String

RealImage

data:byte[]

ImageProxy

filename:String

1 0..1

paint()

paint() paint()

Figure 10-8, Realization of a unidirectional, one-to-one association

public class Advertiser {private Account account;public Advertiser() {

account = new Account();}public Account getAccount() {

return account;}

AccountAdvertiser11

Figure 10-9, Realization of a bidirectional one-to-one association

public class Advertiser extends User{

/* The account field is initialized

* in the constructor and never

* modified. */

private Account account;

public Advertiser() {

account = new Account(this);

public Account getAccount() {

return account;

AccountAdvertiser11

public class Account {/* The owner field is initialized * during the constructor and * never modified. */private Advertiser owner;

public Account(owner:Advertiser) {this.owner = owner;

}public Advertiser getOwner() {

return owner;}

Figure 10-10, Realization of a bidirectional, one-to-many association

public class Advertiser {

private Set accounts;

public Advertiser() {

accounts = new HashSet();

public void addAccount(Account a) {

accounts.add(a);

a.setOwner(this);

public void removeAccount(Account a) {

accounts.remove(a);

a.setOwner(null);

public class Account {

private Advertiser owner;

public void setOwner(Advertiser newOwner) {

if (owner != newOwner) {

Advertiser old = owner;

owner = newOwner;

if (newOwner != null)

newOwner.addAccount(this);

if (oldOwner != null)

old.removeAccount(this);

Advertiser Account1 *

Figure 10-11, Realization of a bidirectional, many-to-many association

public class Tournament {

private List players;

public Tournament() {

players = new ArrayList();

public void addPlayer(Player p) {

if (!players.contains(p)) {

players.add(p);

p.addTournament(this);

public class Player {

private List tournaments;

public Player() {

tournaments = new ArrayList();

public void addTournament(Tournament t) {

if (!tournaments.contains(t)) {

tournaments.add(t);

t.addPlayer(this);

Tournament Player* *

{ordered}

Figure 10-12, Realization of a bidirectional qualified association

PlayernickName0..1*

Object design model before forward engineering

League

Player**

League

Figure 10-12, Realization of a bidirectional qualified association (continued)

public class League {

private Map players;

public void addPlayer(String nickName, Player p) {

if (!players.containsKey(nickName))

players.put(nickName, p);

p.addLeague(nickName, this);

public class Player {

private Map leagues;

public void addLeague

(String nickName, League l) {

if (!leagues.containsKey(l)) {

leagues.put(l, nickName);

l.addPlayer(nickName, this);

Source code after forward engineering

Figure 10-13, Transformation of an association class into an object and two binary associations

Tournament Player* *

Statistics

+getAverageStat(name)+ getTotalStat(name)+ updateStats(match)

Statistics

+getAverageStat(name)+ getTotalStat(name)+ updateStats(match)

Figure 10-14, Example of exception handling in Java.

public class TournamentControl {private Tournament tournament;public void addPlayer(Player p) throws KnownPlayerException {

if (tournament.isPlayerAccepted(p)) {throw new KnownPlayerException(p);

}//... Normal addPlayer behavior

}}public class TournamentForm {

private TournamentControl control;private ArrayList players;public void processPlayerApplications() {

// Go through all the players who applied for this tournamentfor (Iteration i = players.iterator(); i.hasNext();) {

try {// Delegate to the control object.control.acceptPlayer((Player)i.next());

} catch (KnownPlayerException e) {// If an exception was caught, log it to the console, and // proceed to the next player.ErrorConsole.log(e.getMessage());

Figure 10-15, A complete implementation of the Tournament.addPlayer() contract.

Tournament

+isPlayerAccepted(p:Player):boolean+addPlayer(p:Player)

+getMaxNumPlayers():int

-maxNumPlayers: int«precondition»

!isPlayerAccepted(p)

«invariant»getMaxNumPlayers() > 0

«precondition»getNumPlayers() <

getMaxNumPlayers()

+getNumPlayers():int

«postcondition»isPlayerAccepted(p)

Figure 10-16, An example of a relational table, with three attributes and three data records.

login email

“am384” “am384@mail.org”

“js289” “john@mail.de”

User table

firstName

“alice”

“john”

“bd” “bobd@mail.ch”“bob”

Candidate keyCandidate key

Primary key

Figure 10-17, An example of a foreign key. The owner attribute in the League table refers to the primary key of the User table in Figure 10-16.

“am384”

League table

“tictactoeNovice”

“tictactoeExpert”

“js289”“chessNovice”

Foreign key referencing User table

Figure 10-18, Forward engineering of the User class to a database table

+firstName:String+login:String+email:String

id:long firstName:text[25] login:text[8] email:text[32]

User table

Figure 10-19, Mapping of the LeagueOwner/League association as a buried association.

id:long owner:long

LeagueLeagueOwner

LeagueOwner table League table

...... id:long

Figure 10-20, Mapping of the Tournament/Player association as a separate table.

PlayerTournament

Tournament table Player table

tournament player

TournamentPlayerAssociation table

name ...

novice

24 expert

name ...

79 john

Figure 10-21, Realizing the User inheritance hierarchy with a separate table.

Player

LeagueOwner table Player table

User table

maxNumLeagues ...

credits ...

LeagueOwner

name ...

79 john

LeagueOwner

Player

maxNumLeagues credits

Figure 10-22, Realizing the User inheritance hierarchy by duplicating columns.

Player

LeagueOwner table Player table

maxNumLeagues ...

credits ...

LeagueOwner

maxNumLeagues credits

Figure 10-23, Statistics as a product in the Game Abstract Factory

createStatistics()

ChessGameTicTacToeGame

TTTStatistics ChessStatistics

Tournament

Statistics

update()getStat()

DefaultStatistics

Figure 10-24, N-ary association class Statistics relating League, Tournament, and Player

Tournament

0..10..10..1

LeagueGame Player

Statistics

Figure 10-25, SimpleStatisticsVault object realizing the N-ary association of Figure 10-24.

TournamentControl

Statistics

update(match,player)getStatNames()

SimpleStatisticsVault

getStatisticsObject(game,player)getStatisticsObject(league,player)getStatisticsObject(tournament,player)

StatisticsView

createStatistics()

getStat(name)

Figure 10-26, StatisticsVault as a Facade shielding the control and boundary objects from the Statistics storage and computation

TournamentControl

Statistics

update(match,player)getStatNames()

StatisticsVault

update(match)getStatNames(game)getStat(name,game,player)getStat(name,league,player)getStat(name,tournament,player)

StatisticsView

createStatistics()

getStat(name)

Figure 10-27, Public interface of the StatisticsVault class (Java).

public class StatisticsVault {public void update(Match m)

throws InvalidMatch, MatchNotCompleted {...}

public List getStatNames() {...}

public double getStat(String name, Game g, Player p)throws UnknownStatistic, InvalidScope {...}

public double getStat(String name, League l, Player p)throws UnknownStatistic, InvalidScope {...}

public double getStat(String name, Tournament t, Player p)throws UnknownStatistic, InvalidScope {...}

Figure 10-28, Database schema for the Statistics N-ary association of Figure 10-24.

scope:long

Statistics table

player:longscopetype:longid:long

id:long

StatisticCounters table

name:text[25] value:double

id:long

League table

...id:long

Game table

... id:long

Tournament table

Figure 10-29, Associations among Messages, Folders, Mailboxes, and Views in a hypothetical email client

Mailbox Folder Message

Figure 10-30, Associations among League, Tournament, Round, and Player within ARENA

League Tournament Round

Player

figure 10-1, model transformations, refactorings, forward engineering, and reverse engineering

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