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第九章 責(zé)任鏈模式,,1,責(zé)任鏈模式 使多個(gè)對(duì)象都有機(jī)會(huì)處理請(qǐng)求，從而避免請(qǐng)求的發(fā)送者和接收者之間的耦合關(guān)系。將這些對(duì)象連成一條鏈，并沿著這條鏈傳遞該請(qǐng)求，直到有一個(gè)對(duì)象處理它為止。 Chain of Responsibility Pattern Avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request. Chain the receiving objects and pass the request along the chain until an object handles it.,1,2,Chain of Responsibility模式在軍隊(duì)中也有應(yīng)用的例子。某個(gè)下級(jí)軍官要求得到上級(jí)軍官的許可，這個(gè)請(qǐng)求將由其直接上級(jí)軍官再報(bào)給上級(jí)軍官的上級(jí)軍官，直到某個(gè)上級(jí)軍官有權(quán)利做決定為止。如果一名水兵請(qǐng)求進(jìn)入某個(gè)海軍基地，他說(shuō)執(zhí)行的請(qǐng)求過(guò)程就是Chain of Responsibility的實(shí)例。,3,一 、 概述,,4,責(zé)任鏈模式是使用多個(gè)對(duì)象處理用戶請(qǐng)求的成熟模式，責(zé)任鏈模式的關(guān)鍵是將用戶的請(qǐng)求分派給許多對(duì)象，這些對(duì)象被組織成一個(gè)責(zé)任鏈，即每個(gè)對(duì)象含有后繼對(duì)象的引用，并要求責(zé)任鏈上的每個(gè)對(duì)象，如果能處理用戶的請(qǐng)求，就做出處理，不再將用戶的請(qǐng)求傳遞給責(zé)任鏈上的下一個(gè)對(duì)象；如果不能處理用戶的請(qǐng)求，就必須將用戶的請(qǐng)求傳遞給責(zé)任鏈上的下一個(gè)對(duì)象。,4,二、責(zé)任鏈模式的結(jié)構(gòu)與使用,,5,模式的結(jié)構(gòu)中包括兩種角色： 處理者（Handler） 具體處理者（ConcreteHandler）,5,,6,模式的UML類圖,6,aClient aHandler,aConcreteHandler successor,aConcreteHandler successor,,,,,,,,7,模式的結(jié)構(gòu)的描述與使用,用戶提交一個(gè)人的身份證號(hào)碼，想知道該人是否在北京、上?；蛱旖蚓幼　?8,9,1．處理者（Handler）: Handler.java public interface Handler{ public abstract void handleRequest(String number); public abstract void setNextHandler(Handler handler); },9,10,2．具體處理者（ConcreteHandler）_1: Beijing.java public class Beijing implements Handler{ private Handler handler; private ArrayList numberList; Beijing(){ numberList=new ArrayList(); numberList.add(“11129812340930034“); numberList.add(“10120810340930632“); numberList.add(“22029812340930034“); numberList.add(“32620810340930632“); } public void handleRequest(String number){ if(numberList.contains(number)) System.out.println(“該人在北京居住“); else{ System.out.println(“該人不在北京居住“); if(handler!=null) handler.handleRequest(number); } } public void setNextHandler(Handler handler){ this.handler=handler; }},10,11,2．具體處理者（ConcreteHandler）_2: Shanghai.java public class Shanghai implements Handler{ private Handler handler; private ArrayList numberList; Shanghai(){ numberList=new ArrayList(); numberList.add(“34529812340930034“); numberList.add(“98720810340430632“); numberList.add(“36529812340930034“); numberList.add(“77720810340930632“); } public void handleRequest(String number){ if(numberList.contains(number)) System.out.println(“該人在上海居住“); else{ System.out.println(“該人不在上海居住“); if(handler!=null) handler.handleRequest(number); } } public void setNextHandler(Handler handler){ this.handler=handler; } },11,12,2．具體處理者（ConcreteHandler）_3: Tianjin.java public class Tianjin implements Handler{ private Handler handler; private ArrayList numberList; Tianjin(){ numberList=new ArrayList(); numberList.add(“10029812340930034“); numberList.add(“20020810340430632“); numberList.add(“30029812340930034“); numberList.add(“50020810340930632“); } public void handleRequest(String number){ if(numberList.contains(number)) System.out.println(“該人在天津居住“); else{ System.out.println(“該人不在天津居住“); if(handler!=null) handler.handleRequest(number); } } public void setNextHandler(Handler handler){ this.handler=handler; } },12,13,3．應(yīng)用 Application.java public class Application{ private Handler beijing,shanghai,tianjin; public void createChain(){ beijing=new Beijing(); shanghai=new Shanghai(); tianjin=new Tianjin(); beijing.setNextHandler(shanghai); shanghai.setNextHandler(tianjin); } public void reponseClient(String number){ beijing.handleRequest(number); } public static void main(String args[]){ Application application=new Application(); application.createChain(); application.reponseClient(“77720810340930632“);; } },13,三、責(zé)任鏈模式的優(yōu)點(diǎn),,14,責(zé)任鏈中的對(duì)象只和自己的后繼是低耦合關(guān)系，和其他對(duì)象毫無(wú)關(guān)聯(lián)，這使得編寫處理者對(duì)象以及創(chuàng)建責(zé)任鏈變得非常容易。 當(dāng)在處理者中分配職責(zé)時(shí)，責(zé)任鏈給應(yīng)用程序更多的靈活性。 應(yīng)用程序可以動(dòng)態(tài)地增加、刪除處理者或重新指派處理者的職責(zé)。 應(yīng)用程序可以動(dòng)態(tài)地改變處理者之間的先后順序。 使用責(zé)任鏈的用戶不必知道處理者的信息，用戶不會(huì)知道到底是哪個(gè)對(duì)象處理了它的請(qǐng)求。,14,四、應(yīng)用舉例,// Handler.java public interface Handler{ public abstract void compuerMultiply(String number); public abstract void setNextHandler(Handler handler); },15,public class UseInt implements Handler{ private Handler handler; private int result=1 ; public void compuerMultiply(String number){ try{ int n=Integer.parseInt(number); int i=1; while(i=n){ result=result*i; if(result=0){ System.out.println(“超出我的能力范圍，我計(jì)算不了“); puerMultiply(number); return; } i++; } System.out.println(number+“的階乘:“+result); } catch(NumberFormatException exp){ System.out.println(exp.toString()); } } public void setNextHandler(Handler handler){ this.handler=handler; } },16,public class UseLong implements Handler{ private Handler handler; private long result=1 ; public void compuerMultiply(String number){ try{ long n=Long.parseLong(number); long i=1; while(i=n){ result=result*i; if(result=0){ System.out.println(“超出我的能力范圍，我計(jì)算不了“); puerMultiply(number); return; } i++; } System.out.println(number+“的階乘:“+result); } catch(NumberFormatException exp){ System.out.println(exp.toString()); } } public void setNextHandler(Handler handler){ this.handler=handler; } },17,import java.math.BigInteger; public class UseBigInteger implements Handler{ private Handler handler; private BigInteger result=new BigInteger(“1“) ; public void compuerMultiply(String number){ try{ BigInteger n=new BigInteger(number); BigInteger ONE=new BigInteger(“1“); BigInteger i=ONE; while(pareTo(n)=0){ result=result.multiply(i); i=i.add(ONE); } System.out.println(number+“??????:“+result); } catch(NumberFormatException exp){ System.out.println(exp.toString()); } } public void setNextHandler(Handler handler){ this.handler=handler; } },18,public class Application{ private Handler useInt,useLong,useBig; public void createChain(){ useInt=new UseInt(); useLong=new UseLong(); useBig=new UseBigInteger(); useInt.setNextHandler(useLong); useLong.setNextHandler(useBig); } public void reponseClient(String number){ useIpuerMultiply(number); } public static void main(String args[]){ Application application=new Application(); application.createChain(); application.reponseClient(“32“); } },19,