职责链模式.docx
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职责链模式
设计模式读书笔记之职责链模式（chainofresponsibility）收藏
职责链模式：
当一个请求有可能被多个对象处理，则将这些对象连成一条链，并沿着这条链传递请求，直到该请求被处理为止。
单看上图,你肯定看不出职责链模式的特征,先举一个例子来说明一下.比如一个员工想加工资,他首先会告知teamleader,如果在teamleader授权范围之内,则他可以办到,否则,就要请求上级来处理,最后直到老板,于是很容易写出这样的代码来:
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publicclassEmployee{
privateTeamLeadertl;
privateDeptManagerdeptMgr;
privateGeneralManagergm;
privateBossboss;
//someotherproperties
publicvoidaddSalary（intx）{
if（x<=100）{
tl.addSalary（this,x）;
}
elseif（x<=500）{
deptMgr.addSalary（this,x）;
}
elseif（x<=800）{
gm.addSalary（this,x）;
}
else{
boss.addSalary（this,x）;
}
}
//someothermethods
}
publicclassEmployee{
privateTeamLeadertl;
privateDeptManagerdeptMgr;
privateGeneralManagergm;
privateBossboss;
//someotherproperties
publicvoidaddSalary（intx）{
if（x<=100）{
tl.addSalary（this,x）;
}
elseif（x<=500）{
deptMgr.addSalary（this,x）;
}
elseif（x<=800）{
gm.addSalary（this,x）;
}
else{
boss.addSalary（this,x）;
}
}
//someothermethods
}
这个代码中的ifelse带来了坏味道,同时,Employee必须知道他的每一个上司,并使Employee和每一个处理者（他的上司）耦合在一起.其实一个Employee一般来说只需要和他的直接上司打交道就可以了.就如下时序图所示.
把Employee的上司连成一条链,即teamleader持有他的上司部门经理,部门经理持有他的上司总经理,总经理持有他的上司老板.则Employee只需要知道teamleader即可.
加薪代码:
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//
publicinterfaceSupervisor{
publicvoidaddSalary（Employeee,intadded）;
}
///////////////////
publicclassEmployee{
publicStringname;
privateSupervisorsupervisor;
publicEmployee（Stringname）{
this.name=name;
}
publicvoidsetSupervisor（Supervisorsupervisor）{
this.supervisor=supervisor;
}
publicvoidaddSalary（intadded）{
if（supervisor!
=null）{
supervisor.addSalary（this,added）;
}
}
}
///////////////////
publicclassTeamLeaderimplementsSupervisor{
privateSupervisorsuccessor;
publicTeamLeader（Supervisors）{
this.successor=s;
}
publicvoidaddSalary（Employeee,intadded）{
if（added<100）{
System.out.println（"TeamLeader:
"+e.name+"wanttoadd"
+added+"salary,Icanprocessit,done!
"）;
}
elseif（successor!
=null）{
System.out.println（"TeamLeader:
"+e.name+"wanttoadd"
+added+"salary,Ican'tprocessit,butmysupervisorcando!
"）;
successor.addSalary（e,added）;
}
}
}
///////////////////
publicclassDeptManagerimplementsSupervisor{
privateSupervisorsuccessor;
publicDeptManager（Supervisors）{
this.successor=s;
}
publicvoidaddSalary（Employeee,intadded）{
if（added<500）{
System.out.println（"DeptManager:
"+e.name+"wanttoadd"
+added+"salary,Icanprocessit,done!
"）;
}
elseif（successor!
=null）{
System.out.println（"DeptManager:
"+e.name+"wanttoadd"
+added+"salary,Ican'tprocessit,butmysupervisorcando!
"）;
successor.addSalary（e,added）;
}
}
}
///////////////////////
publicclassGeneralManagerimplementsSupervisor{
privateSupervisorsuccessor;
publicGeneralManager（Supervisors）{
this.successor=s;
}
publicvoidaddSalary（Employeee,intadded）{
if（added<800）{
System.out.println（"GeneralManager:
"+e.name+"wanttoadd"
+added+"salary,Icanprocessit,done!
"）;
}
elseif（successor!
=null）{
System.out.println（"GeneralManager:
"+e.name+"wanttoadd"
+added+"salary,Ican'tprocessit,butmysupervisorcando!
"）;
successor.addSalary（e,added）;
}
}
}
//////////////////
publicclassBossimplementsSupervisor{
publicBoss（）{}
publicvoidaddSalary（Employeee,intadded）{
//boss具有最终处理权限,但是他打官腔
System.out.println（"Boss:
Iwillprocessitsoon."）;
}
}
/////////////////////////////
//测试用例
publicclassTest{
publicstaticvoidmain（String[]args）{
Employeee=newEmployee（"Jack"）;
Bossb=newBoss（）;
GeneralManagergm=newGeneralManager（b）;
DeptManagerdm=newDeptManager（gm）;
TeamLeadertl=newTeamLeader（dm）;
e.setSupervisor（tl）;
e.addSalary（1200）;
}
}
/////////////////////////////
//输出
//TeamLeader:
Jackwanttoadd1200salary,Ican'tprocessit,butmysupervisorcando!
//DeptManager:
Jackwanttoadd1200salary,Ican'tprocessit,butmysupervisorcando!
//GeneralManager:
Jackwanttoadd1200salary,Ican'tprocessit,butmysupervisorcando!
//Boss:
Iwillprocessitsoon.
//
publicinterfaceSupervisor{
publicvoidaddSalary（Employeee,intadded）;
}
///////////////////
publicclassEmployee{
publicStringname;
privateSupervisorsupervisor;
publicEmployee（Stringname）{
this.name=name;
}
publicvoidsetSupervisor（Supervisorsupervisor）{
this.supervisor=supervisor;
}
publicvoidaddSalary（intadded）{
if（supervisor!
=null）{
supervisor.addSalary（this,added）;
}
}
}
///////////////////
publicclassTeamLeaderimplementsSupervisor{
privateSupervisorsuccessor;
publicTeamLeader（Supervisors）{
this.successor=s;
}
publicvoidaddSalary（Employeee,intadded）{
if（added<100）{
System.out.println（"TeamLeader:
"+e.name+"wanttoadd"
+added+"salary,Icanprocessit,done!
"）;
}
elseif（successor!
=null）{
System.out.println（"TeamLeader:
"+e.name+"wanttoadd"
+added+"salary,Ican'tprocessit,butmysupervisorcando!
"）;
successor.addSalary（e,added）;
}
}
}
///////////////////
publicclassDeptManagerimplementsSupervisor{
privateSupervisorsuccessor;
publicDeptManager（Supervisors）{
this.successor=s;
}
publicvoidaddSalary（Employeee,intadded）{
if（added<500）{
System.out.println（"DeptManager:
"+e.name+"wanttoadd"
+added+"salary,Icanprocessit,done!
"）;
}
elseif（successor!
=null）{
System.out.println（"DeptManager:
"+e.name+"wanttoadd"
+added+"salary,Ican'tprocessit,butmysupervisorcando!
"）;
successor.addSalary（e,added）;
}
}
}
///////////////////////
publicclassGeneralManagerimplementsSupervisor{
privateSupervisorsuccessor;
publicGeneralManager（Supervisors）{
this.successor=s;
}
publicvoidaddSalary（Employeee,intadded）{
if（added<800）{
System.out.println（"GeneralManager:
"+e.name+"wanttoadd"
+added+"salary,Icanprocessit,done!
"）;
}
elseif（successor!
=null）{
System.out.println（"GeneralManager:
"+e.name+"wanttoadd"
+added+"salary,Ican'tprocessit,butmysupervisorcando!
"）;
successor.addSalary（e,added）;
}
}
}
//////////////////
publicclassBossimplementsSupervisor{
publicBoss（）{}
publicvoidaddSalary（Employeee,intadded）{
//boss具有最终处理权限,但是他打官腔
System.out.println（"Boss:
Iwillprocessitsoon."）;
}
}
/////////////////////////////
//测试用例
publicclassTest{
publicstaticvoidmain（String[]args）{
Employeee=newEmployee（"Jack"）;
Bossb=newBoss（）;
GeneralManagergm=newGeneralManager（b）;
DeptManagerdm=newDeptManager（gm）;
TeamLeadertl=newTeamLeader（dm）;
e.setSupervisor（tl）;
e.addSalary（1200）;
}
}
/////////////////////////////
//输出
//TeamLeader:
Jackwanttoadd1200salary,Ican'tprocessit,butmysupervisorcando!
//DeptManager:
Jackwanttoadd1200salary,Ican'tprocessit,butmysupervisorcando!
//GeneralManager:
Jackwanttoadd1200salary,Ican'tprocessit,butmysupervisorcando!
//Boss:
Iwillprocessitsoon.
上面的代码有两个优点:
1Employee不再依赖于具体的上司,转而依赖于抽象,而且不必知道所有的上司;
2如果新增了处理者,只需要更改客户端代码,即重新构造责任链就可以了.
基础代码：
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packagedesignpattern.chainofresponsibility;
publicabstractclassHandler{
//注意修饰符为protected，因为子类要访问他
protectedHandlersuccessor;
publicvoidsetSuccessor（Handlersuccessor）{
this.successor=successor;
}
publicabstractvoidhandleRequest（intrequest）;
}
//
packagedesignpattern.chainofresponsibility;
publicclassConcreteHandler1extendsHandler{
publicvoidhandleRequest（intrequest）{
if（request>=0&&request<10）{
System.out.println（"requesthandledbyConcreteHandler1"）;
return;
}
if（successor!
=null）{
System.out.println（"ConcreteHandler1can'thandlethisrequest,dispatchtonext."）;
successor.handleRequest（request）;
}
}
}
//
packagedesignpattern.chainofresponsibility;
publicclassConcreteHandler2extendsHandler{
publicvoidhandleRequest（intrequest）{
if（request>=10&&request<20）{
System.out.println（"requesthandledbyConcreteHandler2"）;
return;
}
if（successor!
=null）{
System.out.println（"ConcreteHandler2can'thandlethisrequest,dispatchtonext."）;
successor.handleRequest（request）;
}
}
}
//
packagedesignpattern.chainofresponsibility;
publicclassConcreteHandler3extendsHandler{
publicvoidhandleRequest（intrequest）{
if（request>=20&&request<30）{
System.out.println（"requesthandledbyConcreteHandler3"）;
return;
}
if（successor!
=null）{
System.out.println（"ConcreteHandler3can'thandlethisrequest,dispatchtonext."）;
successor.handleRequest（request）;
}
}
}
//
packagedesignpattern.chainofresponsibility;
publicclassConcreteHandler4extendsHandler{
publicvoidhandleRequest（intrequest）{
if（request>=30）{
System.out.println（"requesthandledbyConcreteHandler3"）;
return;
}
}
}
//客户端测试用例
packagedesignpattern.chainofresponsibility;
publicclassClient{
publicstaticvoidmain（String[]args）{
Handlerhandler1=newConcreteHandler1（）;
Handlerhandler2=newConcreteHandler2（）;
Handlerhandler3=newConcreteHandler3（）;
Handlerhandler4=newConcreteHandler4（）;
handler1.setSuccessor（handler2）;
handler2.setSuccessor（handler3）;
handler3.setSuccessor（handler4）;
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