• 怎么把策略模式和工廠模式結合起來使用

如果大家對策略模式和工廠模式不是很了解的話可以先看前面文章
策略模式：https://www.jianshu.com/p/958281936901
工廠模式：https://www.jianshu.com/p/9078481e00c6

大家可能都用過微信支付，在使用微信支付付錢時候：

1、當我們的付款金額大于我們的余額時，會讓我們使用銀行卡支付，
2、余額充足的時候會讓我們優(yōu)先使用余額里面的錢
扣款策略一：
余額(blance) >= 付款金額(tradeAmout) 使用余額
扣款策略二：
余額(blance) < 付款金額(tradeAmout) 使用銀行卡
很明顯這是一個策略模式的實際應用，但是你還記得策略模式的缺陷嗎？它的具體策略必須暴露出去，而且還要由上層模塊初始化，這不適合，與迪米特法則不符( 迪米特法則（Law of Demeter）又叫作最少知識原則（Least Knowledge Principle 簡寫LKP），就是說一個對象應當對其他對象有盡可能少的了解,不和陌生人說話。注：摘自百度百科，這個迪米特法則下次再細講)沖突。高層模塊對底層模塊僅僅在接觸層次上，而不應該是耦合關系。問題出了，我們應該想辦法解決，正好工廠模式可以幫我們解決這個問題。但是引入工廠模式也有問題，工廠方法要指定一個類，它才能生產(chǎn)對象，我們用枚舉來完成。
首先我們先建兩個實體類WxBlance和WxTrade

import java.math.BigDecimal;/*** @author shuliangzhao* @Title: WxBlance* @ProjectName design-parent* @Description: TODO* @date 2019/5/28 23:50*/ public class WxBlance {//余額private BigDecimal blance;public BigDecimal getBlance() {return blance;}public void setBlance(BigDecimal blance) {this.blance = blance;} } import java.math.BigDecimal;/*** @author shuliangzhao* @Title: Trade* @ProjectName design-parent* @Description: TODO* @date 2019/5/28 23:51*/ public class WxTrade {private BigDecimal tradeAmout;private String tradeNo;private BigDecimal userAmout;public BigDecimal getUserAmout() {return userAmout;}public void setUserAmout(BigDecimal userAmout) {this.userAmout = userAmout;}public String getTradeNo() {return tradeNo;}public void setTradeNo(String tradeNo) {this.tradeNo = tradeNo;}public BigDecimal getTradeAmout() {return tradeAmout;}public void setTradeAmout(BigDecimal tradeAmout) {this.tradeAmout = tradeAmout;} }

扣款策略接口

/*** @author shuliangzhao* @Title: Deduction* @ProjectName design-parent* @Description: TODO* @date 2019/5/28 23:53*/ public interface Deduction {public boolean exec(WxBlance wxBlance,WxTrade wxTrade); }

扣款策略一

/*** @author shuliangzhao* @Title: BlanceDeduction* @ProjectName design-parent* @Description: TODO* @date 2019/5/28 23:54*/ public class BlanceDeduction implements Deduction {@Overridepublic boolean exec(WxBlance wxBlance, WxTrade wxTrade) {if (wxBlance.getBlance().compareTo(wxTrade.getTradeAmout()) >= 0) {wxTrade.setUserAmout(wxBlance.getBlance());}return true;} }

扣款策略二

/*** @author shuliangzhao* @Title: IdCardDeduction* @ProjectName design-parent* @Description: TODO* @date 2019/5/28 23:54*/ public class IdCardDeduction implements Deduction {@Overridepublic boolean exec(WxBlance wxBlance, WxTrade wxTrade) {if (wxBlance.getBlance().compareTo(wxTrade.getTradeAmout()) < 0) {wxTrade.setUserAmout(wxTrade.getTradeAmout());}return true;} }

扣款策略封裝

/*** @author shuliangzhao* @Title: DedutionContext* @ProjectName design-parent* @Description: TODO* @date 2019/5/28 23:58*/ public class DedutionContext {private Deduction deduction;public DedutionContext(Deduction deduction) {this.deduction = deduction;}public boolean exec(WxBlance wxBlance,WxTrade wxTrade) {return deduction.exec(wxBlance,wxTrade);} }

典型的策略上下文。策略模式的缺陷把所有策略類都暴露出去，怎么修改呢？使用工廠模式根據(jù)映射產(chǎn)生策略對象

策略枚舉

/*** @author shuliangzhao* @Title: StrategyEnum* @ProjectName design-parent* @Description: TODO* @date 2019/5/29 0:00*/ public enum StrategyEnum {BlanceDeduction("com.sl.factorystrategy.BlanceDeduction"),IdCardDeduction("com.sl.factorystrategy.IdCardDeduction");String value = "";private StrategyEnum(String value) {this.value = value;}public String getValue() {return value;} }

策略工廠

/*** @author shuliangzhao* @Title: StrategyFactory* @ProjectName design-parent* @Description: TODO* @date 2019/5/29 0:03*/ public class StrategyFactory {public static Deduction getDeduction(StrategyEnum strategyEnum) {Deduction deduction = null;try {deduction = (Deduction)Class.forName(strategyEnum.getValue()).newInstance();} catch (Exception e) {e.printStackTrace();}return deduction;} }

扣款調(diào)用類

/*** @author shuliangzhao* @Title: DeductionFacade* @ProjectName design-parent* @Description: TODO* @date 2019/5/29 0:06*/ public class DeductionFacade {//扣款public static void deduct(WxBlance wxBlance,WxTrade wxTrade) {StrategyEnum strate = getStrate(wxBlance, wxTrade);Deduction deduction = StrategyFactory.getDeduction(strate);deduction.exec(wxBlance,wxTrade);}//獲取扣款策略private static StrategyEnum getStrate(WxBlance wxBlance,WxTrade wxTrade) {if (wxBlance.getBlance().compareTo(wxTrade.getTradeAmout()) < 0) {return StrategyEnum.IdCardDeduction;}else {return StrategyEnum.BlanceDeduction;}} }

調(diào)用客戶端client

/*** @author shuliangzhao* @Title: Client* @ProjectName design-parent* @Description: TODO* @date 2019/5/29 0:10*/ public class Client {public static void main(String[] args) {WxTrade wxTrade = new WxTrade();wxTrade.setTradeAmout(new BigDecimal("1000"));WxBlance wxBlance = new WxBlance();wxBlance.setBlance(new BigDecimal("999"));DeductionFacade.deduct(wxBlance,wxTrade);System.out.println(wxTrade.getUserAmout());} }

執(zhí)行結果

?

image.png

小結：
策略模式：負責對扣款封裝，保證兩個策略自由切換，以后增加策略也很容易

工廠模式：修正策略模式必須對外暴露問題，由工廠模式產(chǎn)生一個具體策略對象

總結

以上是生活随笔為你收集整理的设计模式-策略模式和工厂模式结合使用的全部內(nèi)容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網(wǎng)站內(nèi)容還不錯，歡迎將生活随笔推薦給好友。