(第Ⅲ部分 结构型模式篇) 第11章 外观模式(Façade Pattern)
2011-02-12 16:29
686 查看
概述
在软件开发系统中,客户程序经常会与复杂系统的内部子系统之间产生耦合,而导致客户程序随着子系统的变化而变化。那么如何简化客户程序与子系统之间的交互接口?如何将复杂系统的内部子系统与客户程序之间的依赖解耦?这就是要说的
Façade
模式。
意图
为子系统中的一组接口提供一个一致的界面,
Facade
模式定义了一个高层接口,这个接口使得这一子系统更加容易使用。
[GOF
《设计模式》
]
示意图
门面模式没有一个一般化的类图描述,下面是一个示意性的对象图:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/dee332856bb91015e94b152e9989117c.jpg)
图
1 Façade
模式示意性对象图
生活中的例子
外观模式为子系统中的接口定义了一个统一的更高层次的界面,以便于使用。当消费者按照目录采购时,则体现了一个外观模式。消费者拨打一个号码与客服代表联系,客服代表则扮演了这个
"
外观
"
,他包含了与订货部、收银部和送货部的接口。
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a54c40ac460acf6eabe8b29487f85086.jpg)
图
2
使用电话订货例子的外观模式对象图
[b]Facade
模式解说
[/b]
我们平时的开发中其实已经不知不觉的在用
Façade
模式,现在来考虑这样一个抵押系统,当有一个客户来时,有如下几件事情需要确认:到银行子系统查询他是否有足够多的存款,到信用子系统查询他是否有良好的信用,到贷款子系统查询他有无贷款劣迹。只有这三个子系统都通过时才可进行抵押。我们先不考虑
Façade
模式,那么客户程序就要直接访问这些子系统,分别进行判断。类结构图下:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c371f82ded825d13417f75c1fd537ffa.jpg)
图
3
在这个程序中,我们首先要有一个顾客类,它是一个纯数据类,并无任何操作,示意代码:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
//
顾客类
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
class
Customer
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
private
string
_name;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
Customer(
string
name)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
this
._name
=
name;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
string
Name
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
get
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
return
_name; }
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
下面这三个类均是子系统类,示意代码:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
//
银行子系统
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
class
Bank
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
bool
HasSufficientSavings(Customer c,
int
amount)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Console.WriteLine(
"
Check bank for
"
+
c.Name);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
return
true
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
//
信用子系统
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
class
Credit
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
bool
HasGoodCredit(Customer c)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Console.WriteLine(
"
Check credit for
"
+
c.Name);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
return
true
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
//
贷款子系统
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
class
Loan
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
bool
HasNoBadLoans(Customer c)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Console.WriteLine(
"
Check loans for
"
+
c.Name);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
return
true
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
来看客户程序的调用:
Façade
模式的情况下,客户程序与三个子系统都发生了耦合,这种耦合使得客户程序依赖于子系统,当子系统变化时,客户程序也将面临很多变化的挑战。一个合情合理的设计就是为这些子系统创建一个统一的接口,这个接口简化了客户程序的判断操作。看一下引入
Façade
模式后的类结构图:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
//
客户程序
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
class
MainApp
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
private
const
int
_amount
=
12000
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
static
void
Main()
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Bank bank
=
new
Bank();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Loan loan
=
new
Loan();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Credit credit
=
new
Credit();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Customer customer
=
new
Customer(
"
Ann McKinsey
"
);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
bool
eligible
=
true
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
if
(
!
bank.HasSufficientSavings(customer, _amount))
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
eligible
=
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
else
if
(
!
loan.HasNoBadLoans(customer))
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
eligible
=
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
else
if
(
!
credit.HasGoodCredit(customer))
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
eligible
=
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Console.WriteLine(
"
/n
"
+
customer.Name
+
"
has been
"
+
(eligible
?
"
Approved
"
:
"
Rejected
"
));
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Console.ReadLine();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
可以看到,在不用
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/bec5ee81a8bbc5e74995b04f20ba537e.jpg)
图
4
门面类
Mortage
的实现如下:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
//
外观类
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
class
Mortgage
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
private
Bank bank
=
new
Bank();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
private
Loan loan
=
new
Loan();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
private
Credit credit
=
new
Credit();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
bool
IsEligible(Customer cust,
int
amount)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Console.WriteLine(
"
{0} applies for {1:C} loan/n
"
,
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
cust.Name, amount);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
bool
eligible
=
true
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
if
(
!
bank.HasSufficientSavings(cust, amount))
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
eligible
=
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
else
if
(
!
loan.HasNoBadLoans(cust))
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
eligible
=
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
else
if
(
!
credit.HasGoodCredit(cust))
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
eligible
=
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
return
eligible;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
顾客类和子系统类的实现仍然如下:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
//
银行子系统
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
class
Bank
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
bool
HasSufficientSavings(Customer c,
int
amount)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Console.WriteLine(
"
Check bank for
"
+
c.Name);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
return
true
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
//
信用证子系统
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
class
Credit
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
bool
HasGoodCredit(Customer c)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Console.WriteLine(
"
Check credit for
"
+
c.Name);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
return
true
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
//
贷款子系统
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
class
Loan
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
bool
HasNoBadLoans(Customer c)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Console.WriteLine(
"
Check loans for
"
+
c.Name);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
return
true
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
//
顾客类
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
class
Customer
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
private
string
name;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
Customer(
string
name)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
this
.name
=
name;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
string
Name
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
get
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
return
name; }
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
而此时客户程序的实现:
Façade
模式后,客户程序只与
Mortgage
发生依赖,也就是
Mortgage
屏蔽了子系统之间的复杂的操作,达到了解耦内部子系统与客户程序之间的依赖。
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
//
客户程序类
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
class
MainApp
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
static
void
Main()
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
外观
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Mortgage mortgage
=
new
Mortgage();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Customer customer
=
new
Customer(
"
Ann McKinsey
"
);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
bool
eligable
=
mortgage.IsEligible(customer,
125000
);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Console.WriteLine(
"
/n
"
+
customer.Name
+
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
"
has been
"
+
(eligable
?
"
Approved
"
:
"
Rejected
"
));
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Console.ReadLine();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
可以看到引入
[b].NET
架构中的
Façade
模式
[/b]
Façade
模式在实际开发中最多的运用当属开发
N
层架构的应用程序了,一个典型的
N
层结构如下:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b480fb576e7ef15fe7393e0b38c1f1bd.jpg)
图
5
在这个架构中,总共分为四个逻辑层,分别为:用户层
UI
,业务外观层
Business Façade
,业务规则层
Business Rule
,数据访问层
Data Access
。其中
Business Façade
层的职责如下:
l
从“用户”层接收用户输入
l
如果请求需要对数据进行只读访问,则可能使用“数据访问”层
l
将请求传递到“业务规则”层
l
将响应从“业务规则”层返回到“用户”层
l
在对“业务规则”层的调用之间维护临时状态
对这一架构最好的体现就是
Duwamish
示
例了。在该应用程序中,有部分操作只是简单的从数据库根据条件提取数据,不需要经过任何处理,而直接将数据显示到网页上,比如查询某类别的图书列表。而另
外一些操作,比如计算定单中图书的总价并根据顾客的级别计算回扣等等,这部分往往有许多不同的功能的类,操作起来也比较复杂。如果采用传统的三层结构,这
些商业逻辑一般是会放在中间层,那么对内部的这些大量种类繁多,使用方法也各异的不同的类的调用任务,就完全落到了表示层。这样势必会增加表示层的代码
量,将表示层的任务复杂化,和表示层只负责接受用户的输入并返回结果的任务不太相称,并增加了层与层之间的耦合程度。于是就引入了一个
Façade
层,让这个
Facade
来负责管理系统内部类的调用,并为表示层提供了一个单一
而简单的接口。看一下Duwamish结构图:
![](http://terrylee.cnblogs.com/images/cnblogs_com/terrylee/Facade04.jpg)
图6
从图中可以看到,UI层
将请求发送给业务外观层,业务外观层对请求进行初步的处理,判断是否需要调用业务规则层,还是直接调用数据访问层获取数据。最后由数据访问层访问数据库并按
照来时的步骤返回结果到
UI
层,来看具体的代码实现。
在获取商品目录的时候,
Web UI
调用业务外观层:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
productSystem
=
new
ProductSystem();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
categorySet
=
productSystem.GetCategories(categoryID);
业务外观层直接调用了数据访问层:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
CategoryData GetCategories(
int
categoryId)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
Check preconditions
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
ApplicationAssert.CheckCondition(categoryId
>=
0
,
"
Invalid Category Id
"
,ApplicationAssert.LineNumber);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
Retrieve the data
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
using
(Categories accessCategories
=
new
Categories())
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
return
accessCategories.GetCategories(categoryId);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
在添加订单时,UI调用业务外观层:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
void
AddOrder()
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
ApplicationAssert.CheckCondition(cartOrderData
!=
null
,
"
Order requires data
"
, ApplicationAssert.LineNumber);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
Write trace log.
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
ApplicationLog.WriteTrace(
"
Duwamish7.Web.Cart.AddOrder:/r/nCustomerId:
"
+
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
cartOrderData.Tables[OrderData.CUSTOMER_TABLE].Rows[
0
][OrderData.PKID_FIELD].ToString());
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
cartOrderData
=
(
new
OrderSystem()).AddOrder(cartOrderData);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
业务外观层调用业务规则层:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
OrderData AddOrder(OrderData order)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
Check preconditions
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
ApplicationAssert.CheckCondition(order
!=
null
,
"
Order is required
"
, ApplicationAssert.LineNumber);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
(
new
BusinessRules.Order()).InsertOrder(order);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
return
order;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
业务规则层进行复杂的逻辑处理后,再调用数据访问层:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
bool
InsertOrder(OrderData order)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
Assume it's good
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
bool
isValid
=
true
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
Validate order summary
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
DataRow summaryRow
=
order.Tables[OrderData.ORDER_SUMMARY_TABLE].Rows[
0
];
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
summaryRow.ClearErrors();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
if
(CalculateShipping(order)
!=
(Decimal)(summaryRow[OrderData.SHIPPING_HANDLING_FIELD]))
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
summaryRow.SetColumnError(OrderData.SHIPPING_HANDLING_FIELD, OrderData.INVALID_FIELD);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
isValid
=
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
if
(CalculateTax(order)
!=
(Decimal)(summaryRow[OrderData.TAX_FIELD]))
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
summaryRow.SetColumnError(OrderData.TAX_FIELD, OrderData.INVALID_FIELD);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
isValid
=
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
Validate shipping info
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
isValid
&=
IsValidField(order, OrderData.SHIPPING_ADDRESS_TABLE, OrderData.SHIP_TO_NAME_FIELD,
40
);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
Validate payment info
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
DataRow paymentRow
=
order.Tables[OrderData.PAYMENT_TABLE].Rows[
0
];
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
paymentRow.ClearErrors();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
isValid
&=
IsValidField(paymentRow, OrderData.CREDIT_CARD_TYPE_FIELD,
40
);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
isValid
&=
IsValidField(paymentRow, OrderData.CREDIT_CARD_NUMBER_FIELD,
32
);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
isValid
&=
IsValidField(paymentRow, OrderData.EXPIRATION_DATE_FIELD,
30
);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
isValid
&=
IsValidField(paymentRow, OrderData.NAME_ON_CARD_FIELD,
40
);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
isValid
&=
IsValidField(paymentRow, OrderData.BILLING_ADDRESS_FIELD,
255
);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
Validate the order items and recalculate the subtotal
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
DataRowCollection itemRows
=
order.Tables[OrderData.ORDER_ITEMS_TABLE].Rows;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Decimal subTotal
=
0
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
foreach
(DataRow itemRow
in
itemRows)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
itemRow.ClearErrors();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
subTotal
+=
(Decimal)(itemRow[OrderData.EXTENDED_FIELD]);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
if
((Decimal)(itemRow[OrderData.PRICE_FIELD])
<=
0
)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
itemRow.SetColumnError(OrderData.PRICE_FIELD, OrderData.INVALID_FIELD);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
isValid
=
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
if
((
short
)(itemRow[OrderData.QUANTITY_FIELD])
<=
0
)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
itemRow.SetColumnError(OrderData.QUANTITY_FIELD, OrderData.INVALID_FIELD);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
isValid
=
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
Verify the subtotal
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
if
(subTotal
!=
(Decimal)(summaryRow[OrderData.SUB_TOTAL_FIELD]))
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
summaryRow.SetColumnError(OrderData.SUB_TOTAL_FIELD, OrderData.INVALID_FIELD);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
isValid
=
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
if
( isValid )
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
using
(DataAccess.Orders ordersDataAccess
=
new
DataAccess.Orders())
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
return
(ordersDataAccess.InsertOrderDetail(order))
>
0
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
else
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
return
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
[MSDN]
[b]效果及实现要点
[/b]
1
.
Façade
模式对客户屏蔽了子系统组件,因而减少了客户处理的对象的数目并使得子系统使用起来更加方便。
2
.
Façade
模式实现了子系统与客户之间的松耦合关系,而子系统内部的功能组件往往是紧耦合的。松耦合关系使得子系统的组件变化不会影响到它的客户。
3
.如果应用需要,它并不限制它们使用子系统类。因此你可以在系统易用性与通用性之间选择。
[b]适用性
[/b]
1
.为一个复杂子系统提供一个简单接口。
2
.提高子系统的独立性。
3
.在层次化结构中,可以使用
Facade
模式定义系统中每一层的入口。
[b]总结
[/b]
Façade
模式注重的是简化接口,它更多的时候是从架构的层次去看整个系统,而并非单个类的层次。
[b]参考资料
[/b]
Erich Gamma
等,《设计模式:可复用面向对象软件的基础》,机械工业出版社
Robert C.Martin
,《敏捷软件开发:原则、模式与实践》,清华大学出版社
阎宏,《
Java
与模式》,电子工业出版社
Alan Shalloway James R. Trott
,《
Design Patterns Explained
》,中国电力出版社
MSDN WebCast
《
C#
面向对象设计模式纵横谈
(11)
:
Facade
外观模式
(
结构型模式
)
》
在软件开发系统中,客户程序经常会与复杂系统的内部子系统之间产生耦合,而导致客户程序随着子系统的变化而变化。那么如何简化客户程序与子系统之间的交互接口?如何将复杂系统的内部子系统与客户程序之间的依赖解耦?这就是要说的
Façade
模式。
意图
为子系统中的一组接口提供一个一致的界面,
Facade
模式定义了一个高层接口,这个接口使得这一子系统更加容易使用。
[GOF
《设计模式》
]
示意图
门面模式没有一个一般化的类图描述,下面是一个示意性的对象图:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/dee332856bb91015e94b152e9989117c.jpg)
图
1 Façade
模式示意性对象图
生活中的例子
外观模式为子系统中的接口定义了一个统一的更高层次的界面,以便于使用。当消费者按照目录采购时,则体现了一个外观模式。消费者拨打一个号码与客服代表联系,客服代表则扮演了这个
"
外观
"
,他包含了与订货部、收银部和送货部的接口。
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a54c40ac460acf6eabe8b29487f85086.jpg)
图
2
使用电话订货例子的外观模式对象图
[b]Facade
模式解说
[/b]
我们平时的开发中其实已经不知不觉的在用
Façade
模式,现在来考虑这样一个抵押系统,当有一个客户来时,有如下几件事情需要确认:到银行子系统查询他是否有足够多的存款,到信用子系统查询他是否有良好的信用,到贷款子系统查询他有无贷款劣迹。只有这三个子系统都通过时才可进行抵押。我们先不考虑
Façade
模式,那么客户程序就要直接访问这些子系统,分别进行判断。类结构图下:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c371f82ded825d13417f75c1fd537ffa.jpg)
图
3
在这个程序中,我们首先要有一个顾客类,它是一个纯数据类,并无任何操作,示意代码:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
//
顾客类
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
class
Customer
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
private
string
_name;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
Customer(
string
name)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
this
._name
=
name;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
string
Name
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
get
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
return
_name; }
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
下面这三个类均是子系统类,示意代码:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
//
银行子系统
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
class
Bank
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
bool
HasSufficientSavings(Customer c,
int
amount)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Console.WriteLine(
"
Check bank for
"
+
c.Name);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
return
true
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
//
信用子系统
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
class
Credit
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
bool
HasGoodCredit(Customer c)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Console.WriteLine(
"
Check credit for
"
+
c.Name);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
return
true
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
//
贷款子系统
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
class
Loan
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
bool
HasNoBadLoans(Customer c)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Console.WriteLine(
"
Check loans for
"
+
c.Name);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
return
true
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
来看客户程序的调用:
Façade
模式的情况下,客户程序与三个子系统都发生了耦合,这种耦合使得客户程序依赖于子系统,当子系统变化时,客户程序也将面临很多变化的挑战。一个合情合理的设计就是为这些子系统创建一个统一的接口,这个接口简化了客户程序的判断操作。看一下引入
Façade
模式后的类结构图:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
//
客户程序
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
class
MainApp
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
private
const
int
_amount
=
12000
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
static
void
Main()
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Bank bank
=
new
Bank();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Loan loan
=
new
Loan();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Credit credit
=
new
Credit();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Customer customer
=
new
Customer(
"
Ann McKinsey
"
);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
bool
eligible
=
true
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
if
(
!
bank.HasSufficientSavings(customer, _amount))
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
eligible
=
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
else
if
(
!
loan.HasNoBadLoans(customer))
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
eligible
=
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
else
if
(
!
credit.HasGoodCredit(customer))
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
eligible
=
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Console.WriteLine(
"
/n
"
+
customer.Name
+
"
has been
"
+
(eligible
?
"
Approved
"
:
"
Rejected
"
));
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Console.ReadLine();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
可以看到,在不用
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/bec5ee81a8bbc5e74995b04f20ba537e.jpg)
图
4
门面类
Mortage
的实现如下:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
//
外观类
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
class
Mortgage
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
private
Bank bank
=
new
Bank();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
private
Loan loan
=
new
Loan();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
private
Credit credit
=
new
Credit();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
bool
IsEligible(Customer cust,
int
amount)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Console.WriteLine(
"
{0} applies for {1:C} loan/n
"
,
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
cust.Name, amount);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
bool
eligible
=
true
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
if
(
!
bank.HasSufficientSavings(cust, amount))
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
eligible
=
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
else
if
(
!
loan.HasNoBadLoans(cust))
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
eligible
=
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
else
if
(
!
credit.HasGoodCredit(cust))
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
eligible
=
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
return
eligible;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
顾客类和子系统类的实现仍然如下:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
//
银行子系统
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
class
Bank
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
bool
HasSufficientSavings(Customer c,
int
amount)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Console.WriteLine(
"
Check bank for
"
+
c.Name);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
return
true
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
//
信用证子系统
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
class
Credit
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
bool
HasGoodCredit(Customer c)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Console.WriteLine(
"
Check credit for
"
+
c.Name);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
return
true
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
//
贷款子系统
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
class
Loan
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
bool
HasNoBadLoans(Customer c)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Console.WriteLine(
"
Check loans for
"
+
c.Name);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
return
true
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
//
顾客类
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
class
Customer
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
private
string
name;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
Customer(
string
name)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
this
.name
=
name;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
string
Name
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
get
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
return
name; }
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
而此时客户程序的实现:
Façade
模式后,客户程序只与
Mortgage
发生依赖,也就是
Mortgage
屏蔽了子系统之间的复杂的操作,达到了解耦内部子系统与客户程序之间的依赖。
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
//
客户程序类
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
class
MainApp
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
public
static
void
Main()
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
外观
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Mortgage mortgage
=
new
Mortgage();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Customer customer
=
new
Customer(
"
Ann McKinsey
"
);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
bool
eligable
=
mortgage.IsEligible(customer,
125000
);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Console.WriteLine(
"
/n
"
+
customer.Name
+
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
"
has been
"
+
(eligable
?
"
Approved
"
:
"
Rejected
"
));
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Console.ReadLine();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
可以看到引入
[b].NET
架构中的
Façade
模式
[/b]
Façade
模式在实际开发中最多的运用当属开发
N
层架构的应用程序了,一个典型的
N
层结构如下:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b480fb576e7ef15fe7393e0b38c1f1bd.jpg)
图
5
在这个架构中,总共分为四个逻辑层,分别为:用户层
UI
,业务外观层
Business Façade
,业务规则层
Business Rule
,数据访问层
Data Access
。其中
Business Façade
层的职责如下:
l
从“用户”层接收用户输入
l
如果请求需要对数据进行只读访问,则可能使用“数据访问”层
l
将请求传递到“业务规则”层
l
将响应从“业务规则”层返回到“用户”层
l
在对“业务规则”层的调用之间维护临时状态
对这一架构最好的体现就是
Duwamish
示
例了。在该应用程序中,有部分操作只是简单的从数据库根据条件提取数据,不需要经过任何处理,而直接将数据显示到网页上,比如查询某类别的图书列表。而另
外一些操作,比如计算定单中图书的总价并根据顾客的级别计算回扣等等,这部分往往有许多不同的功能的类,操作起来也比较复杂。如果采用传统的三层结构,这
些商业逻辑一般是会放在中间层,那么对内部的这些大量种类繁多,使用方法也各异的不同的类的调用任务,就完全落到了表示层。这样势必会增加表示层的代码
量,将表示层的任务复杂化,和表示层只负责接受用户的输入并返回结果的任务不太相称,并增加了层与层之间的耦合程度。于是就引入了一个
Façade
层,让这个
Facade
来负责管理系统内部类的调用,并为表示层提供了一个单一
而简单的接口。看一下Duwamish结构图:
![](http://terrylee.cnblogs.com/images/cnblogs_com/terrylee/Facade04.jpg)
图6
从图中可以看到,UI层
将请求发送给业务外观层,业务外观层对请求进行初步的处理,判断是否需要调用业务规则层,还是直接调用数据访问层获取数据。最后由数据访问层访问数据库并按
照来时的步骤返回结果到
UI
层,来看具体的代码实现。
在获取商品目录的时候,
Web UI
调用业务外观层:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
productSystem
=
new
ProductSystem();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
categorySet
=
productSystem.GetCategories(categoryID);
业务外观层直接调用了数据访问层:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
CategoryData GetCategories(
int
categoryId)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
Check preconditions
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
ApplicationAssert.CheckCondition(categoryId
>=
0
,
"
Invalid Category Id
"
,ApplicationAssert.LineNumber);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
Retrieve the data
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
using
(Categories accessCategories
=
new
Categories())
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
return
accessCategories.GetCategories(categoryId);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
在添加订单时,UI调用业务外观层:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
void
AddOrder()
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
ApplicationAssert.CheckCondition(cartOrderData
!=
null
,
"
Order requires data
"
, ApplicationAssert.LineNumber);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
Write trace log.
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
ApplicationLog.WriteTrace(
"
Duwamish7.Web.Cart.AddOrder:/r/nCustomerId:
"
+
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
cartOrderData.Tables[OrderData.CUSTOMER_TABLE].Rows[
0
][OrderData.PKID_FIELD].ToString());
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
cartOrderData
=
(
new
OrderSystem()).AddOrder(cartOrderData);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
业务外观层调用业务规则层:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
OrderData AddOrder(OrderData order)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
Check preconditions
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
ApplicationAssert.CheckCondition(order
!=
null
,
"
Order is required
"
, ApplicationAssert.LineNumber);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
(
new
BusinessRules.Order()).InsertOrder(order);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
return
order;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
业务规则层进行复杂的逻辑处理后,再调用数据访问层:
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a6269e9e4e1e1e402c7d02950e376da4.gif)
public
bool
InsertOrder(OrderData order)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/d697c7f940cec91d060a69b7d6bfbabe.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/78506ac88f008ceb6ff777ee2bfd9158.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
Assume it's good
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
bool
isValid
=
true
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
Validate order summary
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
DataRow summaryRow
=
order.Tables[OrderData.ORDER_SUMMARY_TABLE].Rows[
0
];
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
summaryRow.ClearErrors();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
if
(CalculateShipping(order)
!=
(Decimal)(summaryRow[OrderData.SHIPPING_HANDLING_FIELD]))
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
summaryRow.SetColumnError(OrderData.SHIPPING_HANDLING_FIELD, OrderData.INVALID_FIELD);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
isValid
=
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
if
(CalculateTax(order)
!=
(Decimal)(summaryRow[OrderData.TAX_FIELD]))
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
summaryRow.SetColumnError(OrderData.TAX_FIELD, OrderData.INVALID_FIELD);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
isValid
=
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
Validate shipping info
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
isValid
&=
IsValidField(order, OrderData.SHIPPING_ADDRESS_TABLE, OrderData.SHIP_TO_NAME_FIELD,
40
);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
Validate payment info
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
DataRow paymentRow
=
order.Tables[OrderData.PAYMENT_TABLE].Rows[
0
];
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
paymentRow.ClearErrors();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
isValid
&=
IsValidField(paymentRow, OrderData.CREDIT_CARD_TYPE_FIELD,
40
);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
isValid
&=
IsValidField(paymentRow, OrderData.CREDIT_CARD_NUMBER_FIELD,
32
);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
isValid
&=
IsValidField(paymentRow, OrderData.EXPIRATION_DATE_FIELD,
30
);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
isValid
&=
IsValidField(paymentRow, OrderData.NAME_ON_CARD_FIELD,
40
);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
isValid
&=
IsValidField(paymentRow, OrderData.BILLING_ADDRESS_FIELD,
255
);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
Validate the order items and recalculate the subtotal
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
DataRowCollection itemRows
=
order.Tables[OrderData.ORDER_ITEMS_TABLE].Rows;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
Decimal subTotal
=
0
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
foreach
(DataRow itemRow
in
itemRows)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
itemRow.ClearErrors();
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
subTotal
+=
(Decimal)(itemRow[OrderData.EXTENDED_FIELD]);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
if
((Decimal)(itemRow[OrderData.PRICE_FIELD])
<=
0
)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
itemRow.SetColumnError(OrderData.PRICE_FIELD, OrderData.INVALID_FIELD);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
isValid
=
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
if
((
short
)(itemRow[OrderData.QUANTITY_FIELD])
<=
0
)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
itemRow.SetColumnError(OrderData.QUANTITY_FIELD, OrderData.INVALID_FIELD);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
isValid
=
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
Verify the subtotal
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
//
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
if
(subTotal
!=
(Decimal)(summaryRow[OrderData.SUB_TOTAL_FIELD]))
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
summaryRow.SetColumnError(OrderData.SUB_TOTAL_FIELD, OrderData.INVALID_FIELD);
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
isValid
=
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
if
( isValid )
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
using
(DataAccess.Orders ordersDataAccess
=
new
DataAccess.Orders())
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/b19221674ccfeaa2be2f33591a26176a.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/31fdd64eccd12495cef6cc0af57acfb4.gif)
![](https://oscdn.geek-share.com/Uploads/Images/Content/2015/2015030194/b854634c0904529d4018c4c3336be836.gif)
{
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
return
(ordersDataAccess.InsertOrderDetail(order))
>
0
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/a5a207152d50285d2b642f684cd16367.gif)
}
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
else
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/c8d2e4b59017133d33aed64f31183d35.gif)
return
false
;
![](https://oscdn.geek-share.com/Uploads/Images/Content/201102/f05bd14f49ac5a6f43870a45f107e35f.gif)
}
[MSDN]
[b]效果及实现要点
[/b]
1
.
Façade
模式对客户屏蔽了子系统组件,因而减少了客户处理的对象的数目并使得子系统使用起来更加方便。
2
.
Façade
模式实现了子系统与客户之间的松耦合关系,而子系统内部的功能组件往往是紧耦合的。松耦合关系使得子系统的组件变化不会影响到它的客户。
3
.如果应用需要,它并不限制它们使用子系统类。因此你可以在系统易用性与通用性之间选择。
[b]适用性
[/b]
1
.为一个复杂子系统提供一个简单接口。
2
.提高子系统的独立性。
3
.在层次化结构中,可以使用
Facade
模式定义系统中每一层的入口。
[b]总结
[/b]
Façade
模式注重的是简化接口,它更多的时候是从架构的层次去看整个系统,而并非单个类的层次。
[b]参考资料
[/b]
Erich Gamma
等,《设计模式:可复用面向对象软件的基础》,机械工业出版社
Robert C.Martin
,《敏捷软件开发:原则、模式与实践》,清华大学出版社
阎宏,《
Java
与模式》,电子工业出版社
Alan Shalloway James R. Trott
,《
Design Patterns Explained
》,中国电力出版社
MSDN WebCast
《
C#
面向对象设计模式纵横谈
(11)
:
Facade
外观模式
(
结构型模式
)
》
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