??????Robert%20C.Martin????????(Maintainability)%20???????,??????4?????:

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• ?????

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• ????????????
• ??????Robert C.Martin????????(Maintainability)
  ???????,??????4?????
• ????(Rigidity)
• ????(Fragility)
• ????(Immobility)
• ????(Viscosity)

Robert C.Martin
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??????????

• ????????????
• ?????????Peter Coad??,??????????????????
• ????(Extensibility)
• ???(Flexibility)
• ????(Pluggability)

Peter Coad
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• ????????????
• ?????(Reuse)?????????,????????????,??????,??????,
  ??????????????????
• ?????????????????????????
• ??????????,?????????????????????,???????????????,?
  ????????????????????,????????????

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• ????????????
• ????????????????????????????,??(Refactoring)??????
  ?????????,??????????????????,????????????????,????
  ?????????

Martin Fowler
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• ??????????
• ?????????????7?,????????????,??????,?????

?????? ?????? ???
?????? (Single Responsibility Principle, SRP) ???????,?????????????? ?????
???? (Open-Closed Principle, OCP) ???????????,????????,?????? ??????????????? ?????
?????? (Liskov Substitution Principle, LSP) ??????,???????????????????? ????? ?????
?????? (Dependency Inversion Principle, DIP) ????????,?????????? ?????
?????? (Interface Segregation Principle, ISP) ??????????????????? ?????
?????? (Composite Reuse Principle, CRP) ????????????????????,?????? ???????? ?????
????? (Law of Demeter, LoD) ??????????????????,???????? ????????,?????????????????? ?,????????????????? ?????
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• ????????
• ??????(Single Responsibility Principle, SRP)????
• ??????????????,?????????????????
• ??????
• Every object should have a single responsibility,
  and that responsibility should be entirely
  encapsulated by the class.
• ?????????
• ??????,???????????????
• ??????
• There should never be more than one reason for a
  class to change.

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??????

• ????????
• ???(??????,????)???????,??????????,??????????????,
  ??????????????,??????????,?????????????
• ?????????????????????,????????????,??????????????
  
• ?????????????????????,??????????????????,?????????
  ?????,???????????????????,????????????????????????
  ??????????

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• ????????
• ????
• ???Java?C/S??????????????(Login)??
• ????????????????

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• ????????
• ????

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????

• ??????
• ????(Open-Closed Principle, OCP)????
• ?????????????,????????????????????,???????????????
  ??????,????????????????????????
• ??????
• Software entities should be open for extension,
  but closed for modification.

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????

• ??????
• ?????Bertrand Meyer?1988???,??????????????????
• ?????????,???????????????????????????????????

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????

• ??????
• ????????????
• ???????????????????????????,????????(Principle
  of Encapsulation of Variation, EVP)???????????????
  ????

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• ??????
• ????
• ???????????????????,????????????????,?????????????
  ?????,??????????
• ?????????,????????????

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????

• ??????
• ????

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??????

• ????????
• ??????(Liskov Substitution Principle,
  LSP)???????,???????????,?????
• ?????????S???o1,?????T???o2,???T???????P??????o1??
  ??o2?,??P???????,????S???T?????
• ??????
• If for each object o1 of type S there is an
  object o2 of type T such that for all programs P
  defined in terms of T, the behavior of P is
  unchanged when o1 is substituted for o2 then S is
  a subtype of T.
• ???????????????
• ??????(??)??????????????????
• ??????
• Functions that use pointers or references to base
  classes must be able to use objects of derived
  classes without knowing it.

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??????
???(Jeannette M. Wing),????????,???.??????,???????
????????????????,ACM?IEEE???

• ????????
• ???????2008?????????????????????????????Barbara
  Liskov????.????Jeannette Wing???1994?????????Let
  q(x) be a property provable about objects x of
  type T. Then q(y) should be true for objects y of
  type S where S is a subtype of T.

???????(Barbara Liskov),????????,2008??????,2004?
??.???????,???????,??????????,????????????????????
????????????????????????????
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??????

• ????????
• ???????????????????????????,?????????????????????
  ????,??????????????,???????,??????????????????,???
  ??????????
• ????????????????????,????????????????????,????????
  ??????????????,?????????????,?????????????

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??????

• ????????

???????? ?????? ?
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• ????????
• ????
• ????????????(?????)?????,??????(DataOperator)?????
  ???????????,?????????????,CipherA?CipherB,????????
  ???,?DataOperator?????????????????????

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• ????????
• ????
• ?????????????????????????????,??CipherA??CipherB,?
  ???????Client??????DataOperator????,????????
• ???????????????,??????????,???????

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• ????????
• ????

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• ????????
• ??????(Dependence Inversion Principle, DIP)?????
• ?????????????,????????????????????,??????????
• ??????
• High level modules should not depend upon low
  level modules, both should depend upon
  abstractions. Abstractions should not depend upon
  details, details should depend upon abstractions.
• ??????
• ???????,?????????
• ??????
• Program to an interface, not an implementation.

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• ????????
• ???????Robert C. Martin?1996??C
  Reporter?????Engineering Notebook????,???????2002
  ????????Agile Software Development, Principles,
  Patterns, and Practices??

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• ????????
• ????,???????????????????,?????????????????????,?
  ??????????
• ?????????????,?????????????,???????????????????,??
  ????????????????????

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• ????????
• ?????????????????????????,?????????????
• ???????,????????
• Put Abstractions in Code, Details in Metadata
• (?????????????(The Pragmatic programmer from
  journeyman to master) )

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• ????????
• ??????
• ?????
• ??????
• ??????
• ??????????????????,??????????????????

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• ????????
• ????

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??????

• ????????
• ????
• ????(Constructor Injection)?????????????
• ????(Setter Injection)??Setter?????????
• ????(Interface Injection)?????????????

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??????

• ????????
• ????
• ?????????????,????????????????????,?????????????(D
  atabaseSource)???????????????(TextSource),????????
  ?XML??(XMLTransformer)?????XLS??(XLSTransformer)??

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??????

• ????????
• ????
• ???????,??????????????????????,???????????????????
  ?????,???MainClass????????,???????,???????????????
  ??????????

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??????

• ????????
• ????

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??????

• ????????
• ??????(Interface Segregation Principle,
  ISP)?????
• ??????????????????
• ??????
• Clients should not be forced to depend upon
  interfaces that they do not use.
• ??,??????????????????
• ?????????
• ????????,????????????????,???????????????????????
• ??????
• Once an interface has gotten too 'fat' it needs
  to be split into smaller and more specific
  interfaces so that any clients of the interface
  will only know about the methods that pertain to
  them.

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• ????????
• ?????????????????,?????????????????????????????,??
  ??,???????,????????
• (1) ????????????,??????????????,????????????????
  ?
• (2) ??????????????,??????,??????????????,?????????
  ?????????,???????????

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• ????????
• ?????????????,????????????,????????????????,??????
  ?????,???????????
• ???????????????????,?????????????????,??????????,?
  ???????????

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• ????????
• ????
• ?????????????????,??????????????(???)AbstractServi
  ce???????????????????????????

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• ????????
• ????

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• ????????
• ??????(Composite Reuse Principle,
  CRP)?????/??????(Composition/ Aggregate Reuse
  Principle, CARP),?????
• ????????,??????????????
• ??????
• Favor composition of objects over inheritance as
  a reuse mechanism.

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• ????????
• ???????????????????????(???????????)??????????,???
  ???????????????????????????????????????????????/
  ????,?????

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• ????????,???????????????????????????,?????/???????
  ???
• ????????,???????????????????????????,???????????
  ,????????????????????(???? )
• ??/???????????,????????????????????????(???? )

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• ????????
• ??/???????????,???????????,???????????????????,???
  ???????/??????????????,??????,????????????,??????
  ??????????,?????,????????????????????????????,????
  ?????????

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• ????????
• ????
• ?????????????????????

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??????

• ????????
• ????
• ?????????????,?????JDBC?????,????????????,?????DBU
  til???????StudentDAO??JDBC??,??TeacherDAO???????,?
  ????????DBUtil?,???StudentDAO?TeacherDAO????,?????
  ???????,????????,????????
• ????????????????

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??????

• ????????
• ????

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?????

• ???????
• ?????(Law of Demeter, LoD)?????????(Least
  Knowledge Principle, LKP),????????,??????????
• (1) ??????????????Don't talk to strangers.
• (2) ????????????????Talk only to your immediate
  friends.
• (3) ?????????????????????,????????????????????????
  ??Each unit should have only limited knowledge
  about other units only units "closely" related
  to the current unit.

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?????

• ???????
• ????????1987????????(Northeastern
  University)????Demeter??????
• ????,???????????????????????????????????,????????,
  ?????????????,???????,??????????????,?????????????
  ???????

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?????

• ???????
• ???????,??????,?????????
• (1) ??????(this)
• (2) ??????????????????
• (3) ?????????
• (4) ????????????????,?????????????
• (5) ???????????
• ??????,???????????,?????????,????????

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• ????????????????????????????,???????????????,?????
  ??????????????,????????????????????????,??????????
  ????

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• ??????????????????,??????????????????????????,???
  ????????????,???????????????????????,?????????????
  ?????????,?????????????????
• ????????????????????????????????,????????????????
  ?????????????,?????????????????????,???????????,??
  ?????????????????,???????????????????????????????,
  ?????????,???????????????

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• ??????,???????????,?????????,???????,?????????????
  ??,?????????????
• ????????,??????????????????????????
• ??????,?????,????????????
• ?????????,???????????????????

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• ???????
• ????
• ??????(?Form1?Form2??)??????(?DAO1?DAO2??)????????
  ???,????

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• ???????
• ????

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• ???????????????,??????????,????????????
• ????????????????,??????,??????,??????????????????
• ??????????????,???????????????????
• ???????????????????,?????,??????????????????????
• ???????????????????????????,??????????????

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• ??????????????????,????????????????,?????????
• ?????????????????????????,????????????????????????
  
• ???????????????????,???????
• ????????????????????????????????

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END
Thanks!