责任链模式
Chain of Responsibility
- 什么是责任链模式
- 如何实现责任链模式
- 责任链模式如何解耦
- 责任链模式的应用
生活中的COR
- 击鼓传花
- 申请折扣
天然的责任链:公司层级结构
- CEO
- Vice President
- Director/Manager
- Sales
Handler:Sales->Manager->Director->Vice President->CEO
Client: 老张、王老板、小王 request
有求必应的销售团队
- CEO <=55%
- Vice President <=50%
- Director <=40%
- Manager <=30%
- Sales <=5%
PriceHandler接口
package com.evior.designPattern.pricehandler;
import com.evior.designPattern.factory.PriceHandlerFactory;
public abstract class PriceHandler {
/*
* 直接后继,用于传递请求
*/
protected PriceHandler successor;
public void setSuccessor(PriceHandler successor) {
this.successor = successor;
}
/*
* 处理折扣申请
*/
public abstract void processDiscount(float discount);
/*
* 创建PriceHandler的工厂方法
*/
public static PriceHandler createPriceHandler() {
PriceHandlerFactory priceHandlerFactory=new PriceHandlerFactory();
PriceHandler priceHandler = priceHandlerFactory.createPriceHandler();
return priceHandler;
}
}
SalesPriceHandler <=5%
package com.evior.designPattern.pricehandler;
public class SalesPriceHandler extends PriceHandler {
@Override
public void processDiscount(float discount) {
if(discount <= 0.05){
System.out.format("%s批准了折扣:%.2f%n", this.getClass().getName(), discount);
}else{
//报告给上一级
successor.processDiscount(discount);
}
}
}
LeadPriceHandler <=15%
package com.evior.designPattern.pricehandler;
public class LeadPriceHandler extends PriceHandler {
@Override
public void processDiscount(float discount) {
if(discount<=0.15){
System.out.format("%s批准了折扣:%.2f%n",this.getClass().getName(),discount);
}else{
//报告给上一级
successor.processDiscount(discount);
}
}
}
ManagerPriceHandler <=30%
package com.evior.designPattern.pricehandler;
public class ManagerPriceHandler extends PriceHandler {
@Override
public void processDiscount(float discount) {
if(discount<=0.3){
System.out.format("%s批准了折扣:%.2f%n",this.getClass().getName(),discount);
}else{
//报告给上一级
successor.processDiscount(discount);
}
}
}
DirectorPriceHandler <=40%
package com.evior.designPattern.pricehandler;
public class DirectorPriceHandler extends PriceHandler {
@Override
public void processDiscount(float discount) {
if(discount<=0.4){
System.out.format("%s批准了折扣:%.2f%n",this.getClass().getName(),discount);
}else{
//报告给上一级
successor.processDiscount(discount);
}
}
}
VicePresidentPriceHandler <=50%
package com.evior.designPattern.pricehandler;
public class VicePresidentPriceHandler extends PriceHandler {
@Override
public void processDiscount(float discount) {
if(discount<=0.5){
System.out.format("%s批准了折扣:%.2f%n",this.getClass().getName(),discount);
}else{
//报告给上一级
successor.processDiscount(discount);
}
}
}
CEOPriceHandler <=55%
package com.evior.designPattern.pricehandler;
public class CEOPriceHandler extends PriceHandler {
@Override
public void processDiscount(float discount) {
if(discount<=0.55){
System.out.format("%s批准了折扣:%.2f%n",this.getClass().getName(),discount);
}else{
//报告给上一级
System.out.format("%s拒绝了折扣:%.2f%n", this.getClass().getName(),discount);
}
}
}
PriceHandlerFactory
package com.evior.designPattern.factory;
import com.evior.designPattern.pricehandler.*;
/**
* 工厂
* 构建责任链
* 返回最底层
*/
public class PriceHandlerFactory {
/*
* 创建PriceHandler的工厂方法
*/
public static PriceHandler createPriceHandler() {
PriceHandler sales = new SalesPriceHandler();
PriceHandler lead = new LeadPriceHandler();
PriceHandler man = new ManagerPriceHandler();
PriceHandler dir = new DirectorPriceHandler();
PriceHandler vp = new VicePresidentPriceHandler();
PriceHandler ceo = new CEOPriceHandler();
//设置sale的上一级
sales.setSuccessor(lead);
//设置sale的上一级
lead.setSuccessor(man);
//设置sale的上一级
man.setSuccessor(dir);
//设置sale的上一级
dir.setSuccessor(vp);
//设置sale的上一级
vp.setSuccessor(ceo);
//最底层
return sales;
}
}
Customer
package com.evior.designPattern.customer;
import com.evior.designPattern.pricehandler.PriceHandler;
import java.util.Random;
public class Customer {
private PriceHandler priceHandler;
public void setPriceHandler(PriceHandler priceHandler) {
this.priceHandler = priceHandler;
}
public void requestDiscount(float discount){
priceHandler.processDiscount(discount);
}
}
测试
package com.evior.designPattern;
import com.evior.designPattern.customer.Customer;
import com.evior.designPattern.pricehandler.PriceHandler;
import java.util.Random;
public class Test {
public static void main(String[] args){
Customer customer = new Customer();
customer.setPriceHandler(PriceHandler.createPriceHandler());
Random rand = new Random();
for(int i=1;i<=10;i++){
System.out.print(i+":");
customer.requestDiscount(rand.nextFloat());
}
}
}
结果
构建图
剖析责任链模式
在责任链模式中,作为请求接收者的多个对象通过对其后继的引用而连接起来形成一
条链。请求在这条链上传递,直到链上某一个接收者处理这个请求。每个接收者都可
以选择自行处理请求或是向后继传递请求。
依赖于抽象不依赖于具体
发送请求的客户端并不知道链上的哪一个接收者会处理这个请求,从而实现了客户端
和接收者之间的解耦。
真的好吗?
- 开闭原则
扩展开放,修改关闭
永远没有正确答案,取决于项目实际对降低耦合的要求是什么,是否有其他替代方案,
根据实际情况取舍而来 - 执行性能
处理器首尾相接,有请求时需要遍历链
时间、内存
awt早期使用责任链模式,现在改为了观察者模式
责任链模式的应用
Exception Handling
main->Method with an exception handler->Method without an exception handler->Method where error occurred
JavaScript Event Model
capture phase(捕获) -> target phase -> bubbling phase(冒泡)
FilterChain in Web
设计模式和oo的基本原则