第十章 将模型映射到代码.pptVIP

一对多关联 public class Advertiser{ private Set accounts; public Advertiser(){ account = new HashSet(); } public void addAccount(Account a){ accounts.add(a); a.setOwner(this); } } public class Account{ private Advertiser Owner; public void setOwner(Advertiser Owner){ this.owner=Owner; Owner.addAccount(this); } …………. } 多对多关联 public class Tournament{ private List players; public Tournament(){ palyers = new ArrayList(); } public void addPlayer(Player p){ if(!players.contain(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.contain(t)){ tournaments.add(p); t.addPlayer(this); }}} 受限关联 public class Tournament{ private Map players; public void addPlayer (String nickname, Player p) { if(!players.containKey(nickName)){ players.put(nickName,p); p.addTournament(nickName,this); }}} public class Player{ private Map tournaments; public void addTournament (String nickname, Tournament t){ if(!tournaments.containKey(nickName,t)){ tournaments.put(nickName,t); t.addPlayer(nickName,t); }}} 映射活动-将契约映射到异常 面向对象语言没有对契约进行支持 一般使用异常机制来处理契约事故 public class Tournament{ //....... private List players; public addPlayer(Player p) throws knownPlayer, TooManyPlayers,UnknownPlayer, IllegalNumPlayers,IllegalMaxNumPlayers{ //check precondition !isPlayerAccepted(p) if(isPlayerAccepted(p)) throw new knownPlayer(p); //check precondition getNumPlayers()maxNumPlayers if(getNumPlayers()==getMaxNumPlayers()) throw new TooManyPlayers(getNumPlayers()); ..... //save current player num int pre_getNumPlayers = getNumPlayers(); //check postcondition isPlayerAccepted(p) if(!isPlayerAccepted(p)) throw new unKnownPlayer(p); //check po