Java敏捷开发技巧之消除代码异味

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Java敏捷开发技巧之消除代码异味

发表于：2011-9-28 09:33

作者：yongbing 来源：51Testing软件测试网采编

　　用一个对象代替一种类别（注意，之前是一个类代替一种类别）。

　　根据之前讲的解决方法，要去掉类别代码，我们只需要为每种类别创建一个子类，比如：

abstract class UserAccount {
String id;   
String name; 
String password; 
Date dateOfLastPasswdChange; 
abstract int getPasswordMaxAgeInDays();  
abstract boolean canPrintReport();   
}   
class NormalUserAccount extends UserAccount {   
int getPasswordMaxAgeInDays() {  
return 90;   
}
boolean canPrintReport() {   
return true; 
}
}   
class AdminUserAccount extends UserAccount {
int getPasswordMaxAgeInDays() {  
return 30;   
}
boolean canPrintReport() {   
return true; 
}
}   
class GuestUserAccount extends UserAccount {
int getPasswordMaxAgeInDays() {  
return Integer.MAX_VALUE;
}
boolean canPrintReport() {   
return false;
}
}

　　但问题是，三种子类的行为（里面的代码）都差不多一样，getPasswordMaxAgeInDays这个方法就一个数值不同（30,90或者Integer.MAX_VALUE)。canPrintReport这个方法也不同在一个数值（true或false）。这三种用户类型只需要用三个对象代替就行了，无须特别地新建三个子类了：

class UserAccount {
UserType userType;
String id;
String name;
String password;
Date dateOfLastPasswdChange;
UserType getType() {
return userType;
}
}
class UserType {
int passwordMaxAgeInDays;
boolean allowedToPrintReport;
UserType(int passwordMaxAgeInDays, boolean allowedToPrintReport) {
this.passwordMaxAgeInDays = passwordMaxAgeInDays;
this.allowedToPrintReport = allowedToPrintReport;
}
int getPasswordMaxAgeInDays() {
return passwordMaxAgeInDays;
}
boolean canPrintReport() {
return allowedToPrintReport;
}
static UserType normalUserType = new UserType(90, true);
static UserType adminUserType = new UserType(30, true);
static UserType guestUserType = new UserType(Integer.MAX_VALUE, false);
}
class InventoryApp {
void login(UserAccount userLoggingIn, String password) {
if (userLoggingIn.checkPassword(password)) {
GregorianCalendar today = new GregorianCalendar();
GregorianCalendar expiryDate = getAccountExpiryDate(userLoggingIn);
if (today.after(expiryDate)) {
//提示用户修改密码
...
}
}
}
GregorianCalendar getAccountExpiryDate(UserAccount account) {
int passwordMaxAgeInDays = getPasswordMaxAgeInDays(account);
GregorianCalendar expiryDate = new GregorianCalendar();
expiryDate.setTime(account.dateOfLastPasswdChange);
expiryDate.add(Calendar.DAY_OF_MONTH, passwordMaxAgeInDays);
return expiryDate;
}
int getPasswordMaxAgeInDays(UserAccount account) {
return account.getType().getPasswordMaxAgeInDays();
}
void printReport(UserAccount currentUser) {
boolean canPrint;
canPrint = currentUser.getType().canPrintReport();
if (!canPrint) {
throw new SecurityException("You have no right");
}
//打印报表.
}
}

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