策略模式

定义：指对一系列的算法定义，并将每一个算法封装起来，而且使它们还可以相互替换。策略模式让算法独立于使用它的客户而独立变化。

简易UML图

第8节：策略模式（Strategy Pattern） - 图1

需求分析

每当节假日来临，众多商品就会进行相应折扣，以此来吸引客户，不同的节日，有不同寓意，也就是说，不同的节日，某些商品将赋予特定价值，而这时带来了巨大的需求，市场供求过大。为竞争其他商户，为自家商品迎来订单，这时就需要饥饿效应，玩打折来吸引客户。
可到底是哪些商品进行打折，以及每个商品需要打多少折扣，既保证吸引客户，又能保证赚钱。这就需要为商品分类进行算法得出，同时在业务中，我们很可能要写异常多的类，如果杂糅在一起，那对于维护极不方便。
而策略模式，就是可以将每个单独商品分类价格处理，避免代码的耦合性太高。

具体实现

第8节：策略模式（Strategy Pattern） - 图2

定义接口

  1. package com.test.strategy;
  3. import com.test.domain.Goods;
  5. /** 
  6.  * 策略方法
  7.  * @author 12134
  8.  *
  9.  */
  10. public interface IJRStrategy {
  11.     /** 
  12.      * 活动，每个活动都有特定的商品奖励活动，该商品活动根据算法计算出来
  13.      */
  14.     String activity(Goods goods);
  15. }

自定义接口

用于判断该活动属于那个节日。

  1. package com.test.annotation;
  3. import java.lang.annotation.Documented;
  4. import java.lang.annotation.ElementType;
  5. import java.lang.annotation.Retention;
  6. import java.lang.annotation.RetentionPolicy;
  7. import java.lang.annotation.Target;
  9. import com.test.enums.ActivityJREnum;
  11. /** 
  12.  * 节日商品注解
  13.  * @author 12134
  14.  *
  15.  */
  16. @Documented
  17. @Target(ElementType.TYPE)
  18. @Retention(RetentionPolicy.RUNTIME)
  19. public @interface JRGoodSource {
  21.     ActivityJREnum value();
  23. }

定义节日枚举类

  1. package com.test.enums;
  3. public enum ActivityJREnum {
  5.     /**
  6.      * 七夕节
  7.      */
  8.     QIXIJIE(1,"七夕节"),
  10.     /**
  11.      * 劳动节
  12.      */
  13.     LAODONGJIE(2,"劳动节"),
  14.     /**
  15.      * 元宵节
  16.      */
  17.     YUANXIAOJIE(3,"元宵节");
  19.     private Integer code;
  20.     private String name;
  22.     ActivityJREnum() {
  23.     }
  25.     ActivityJREnum(Integer code, String name) {
  26.         this.code = code;
  27.         this.name = name;
  28.     }
  30.     public Integer getCode() {
  31.         return code;
  32.     }
  34.     public String getName() {
  35.         return name;
  36.     }
  38. }

定义接口实现类

也是算法和业务处理的地方。

  1. package com.test.strategy.impl;
  3. import java.text.DecimalFormat;
  5. import com.test.annotation.JRGoodSource;
  6. import com.test.domain.Goods;
  7. import com.test.enums.ActivityJREnum;
  8. import com.test.strategy.IJRStrategy;
  10. /** 
  11.  * 劳动节
  12.  * @author 12134
  13.  *
  14.  */
  15. @JRGoodSource(ActivityJREnum.LAODONGJIE)
  16. public class LaoDongJR implements IJRStrategy{
  18.     /**
  19.      * 商品的价格打折处理
  20.      */
  21.     @Override
  22.     public String activity(Goods goods) {
  23.         // 劳动节特定商品打七折
  24.         DecimalFormat df =new DecimalFormat("#.00");
  25.         String result = df.format(goods.getPrice()*0.7);
  26.         return result;
  27.     }
  29. }
  1. package com.test.strategy.impl;
  3. import java.text.DecimalFormat;
  5. import com.test.annotation.JRGoodSource;
  6. import com.test.domain.Goods;
  7. import com.test.enums.ActivityJREnum;
  8. import com.test.strategy.IJRStrategy;
  10. /**
  11.  * 七夕节 情侣专用的商品 算法得出：销量最好的，玫瑰、巧克力、酒店等等商品
  12.  * 
  13.  * @author 12134
  14.  *
  15.  */
  16. @JRGoodSource(ActivityJREnum.QIXIJIE)
  17. public class QixiJR implements IJRStrategy {
  19.     /**
  20.      * 商品的打折处理
  21.      * @param price 商品价格
  22.      */
  23.     @Override
  24.     public String activity(Goods goods) {
  25.         // 情人节特定商品打八折
  26.         DecimalFormat df =new DecimalFormat("#.00");
  27.         String result = df.format(goods.getPrice()*0.8);
  28.         return result;
  29.     }
  31. }
  1. package com.test.strategy.impl;
  3. import java.text.DecimalFormat;
  5. import com.test.annotation.JRGoodSource;
  6. import com.test.domain.Goods;
  7. import com.test.enums.ActivityJREnum;
  8. import com.test.strategy.IJRStrategy;
  10. /**
  11.  * 元宵节
  12.  * 
  13.  * @author 12134
  14.  *
  15.  */
  16. @JRGoodSource(ActivityJREnum.YUANXIAOJIE)
  17. public class YuanXiaoJR implements IJRStrategy {
  19.     /**
  20.      * 商品的打折处理
  21.      */
  22.     @Override
  23.     public String activity(Goods goods) {
  24.         // 元宵节特定商品打九折
  25.         DecimalFormat df =new DecimalFormat("#.00");
  26.         String result = df.format(goods.getPrice()*0.9);
  27.         return result;
  28.     }
  30. }

定义pojo

  1. package com.test.domain;
  3. public class Goods {
  4.     /**
  5.      * 商品编号
  6.      */
  7.     private String no;
  8.     /**
  9.      * 商品名称
  10.      */
  11.     private String name;
  12.     /**
  13.      * 商品价格
  14.      */
  15.     private Double price;
  16.     /**
  17.      * 本次活动名 1：七夕节，2：劳动节，3：元宵节
  18.      */
  19.     private Integer sourceFlg;
  20.     /**
  21.      * 活动折扣和提示信息
  22.      */
  23.     private Discount discount;
  25.     public String getNo() {
  26.         return no;
  27.     }
  29.     public void setNo(String no) {
  30.         this.no = no;
  31.     }
  33.     public String getName() {
  34.         return name;
  35.     }
  37.     public void setName(String name) {
  38.         this.name = name;
  39.     }
  41.     public Double getPrice() {
  42.         return price;
  43.     }
  45.     public void setPrice(Double price) {
  46.         this.price = price;
  47.     }
  49.     public Integer getSourceFlg() {
  50.         return sourceFlg;
  51.     }
  53.     public void setSourceFlg(Integer sourceFlg) {
  54.         this.sourceFlg = sourceFlg;
  55.     }
  57.     public Discount getDiscount() {
  58.         return discount;
  59.     }
  61.     public void setDiscount(Discount discount) {
  62.         this.discount = discount;
  63.     }
  65.     public Goods() {
  66.         super();
  67.     }
  69.     public Goods(String no, String name, Double price, Integer sourceFlg) {
  70.         super();
  71.         this.no = no;
  72.         this.name = name;
  73.         this.price = price;
  74.         this.sourceFlg = sourceFlg;
  75.     }
  77.     public Goods(String no, String name, Double price, Integer sourceFlg, Discount discount) {
  78.         super();
  79.         this.no = no;
  80.         this.name = name;
  81.         this.price = price;
  82.         this.sourceFlg = sourceFlg;
  83.         this.discount = discount;
  84.     }
  86.     @Override
  87.     public String toString() {
  88.         return "Goods [no=" + no + ", name=" + name + ", price=" + price + ", sourceFlg=" + sourceFlg + ", discount="
  89.                 + discount + "]";
  90.     }
  92. }
  1. package com.test.domain;
  3. import java.io.Serializable;
  5. /**
  6.  * 商品折扣
  7.  * 
  8.  * @author 12134
  9.  *
  10.  */
  11. public class Discount implements Serializable {
  12.     private static final long serialVersionUID = 1L;
  13.     /**
  14.      * 折扣编号
  15.      */
  16.     private int no;
  17.     /**
  18.      * 折扣信息
  19.      */
  20.     private String message;
  21.     /**
  22.      * 节日提示信息
  23.      */
  24.     private String jieRi;
  26.     public int getNo() {
  27.         return no;
  28.     }
  30.     public void setNo(int no) {
  31.         this.no = no;
  32.     }
  34.     public String getMessage() {
  35.         return message;
  36.     }
  38.     public void setMessage(String message) {
  39.         this.message = message;
  40.     }
  42.     public String getJieRi() {
  43.         return jieRi;
  44.     }
  46.     public void setJieRi(String jieRi) {
  47.         this.jieRi = jieRi;
  48.     }
  50.     public Discount(int no, String message, String jieRi) {
  51.         super();
  52.         this.no = no;
  53.         this.message = message;
  54.         this.jieRi = jieRi;
  55.     }
  57.     public Discount() {
  58.         super();
  59.     }
  61.     @Override
  62.     public String toString() {
  63.         return "Discount [no=" + no + ", message=" + message + ", jieRi=" + jieRi + "]";
  64.     }
  66. }
  1. package com.test.domain;
  3. import java.io.Serializable;
  5. public class ResponseMessage implements Serializable {
  6.     private static final long serialVersionUID = 1L;
  8.     private Integer code;
  9.     private Object data;
  10.     private String msg;
  12.     public Integer getCode() {
  13.         return code;
  14.     }
  16.     public void setCode(Integer code) {
  17.         this.code = code;
  18.     }
  20.     public Object getData() {
  21.         return data;
  22.     }
  24.     public void setData(Object data) {
  25.         this.data = data;
  26.     }
  28.     public String getMsg() {
  29.         return msg;
  30.     }
  32.     public void setMsg(String msg) {
  33.         this.msg = msg;
  34.     }
  36.     public ResponseMessage(Integer code, Object data, String msg) {
  37.         super();
  38.         this.code = code;
  39.         this.data = data;
  40.         this.msg = msg;
  41.     }
  43.     public ResponseMessage() {
  44.         super();
  45.     }
  47.     @Override
  48.     public String toString() {
  49.         return "ResponseMessage [code=" + code + ", data=" + data + ", msg=" + msg + "]";
  50.     }
  52. }

定义处理接口调用

  1. package com.test.strategy.context;
  3. import java.util.List;
  4. import java.util.Map;
  5. import java.util.concurrent.ConcurrentHashMap;
  7. import com.test.domain.Goods;
  8. import com.test.strategy.IJRStrategy;
  10. public class JRSimpleContext {
  12.     private final Map<Integer, IJRStrategy> strategyMap = new ConcurrentHashMap<>();
  14.     /**
  15.      * 构造函数
  16.      * 
  17.      * @param strategyMap
  18.      */
  19.     public JRSimpleContext(Map<Integer, IJRStrategy> strategyMap) {
  20.         this.strategyMap.clear();
  21.         strategyMap.forEach((k, v) -> this.strategyMap.put(k, v));
  22.     }
  24.     /**
  25.      * 商品订单编号处理
  26.      * 
  27.      * @param requestId
  28.      * @return
  29.      */
  30.     public List<Goods> getSource(List<Goods> goodsInfo) {
  31.         System.out.println(strategyMap);
  32.         for (int i = 0; i < goodsInfo.size(); i++) {
  33.             Goods goods2 = goodsInfo.get(i);
  34.             // 如果订单商品编号不为空
  35.             if (strategyMap.get(goodsInfo.get(i).getSourceFlg()) != null) {
  36.                 // 获取该活动的价格
  37.                 String price = strategyMap.get(goodsInfo.get(i).getSourceFlg()).activity(goods2);
  38.                 goods2.setPrice(Double.valueOf(price));
  39.             } else {
  40.                 System.out.println("你选购的商品不符合本次活动，暂不享受优惠，感谢你的使用！");
  41.             }
  42.         }
  43.         return goodsInfo;
  44.     }
  46. }

定义主方法

  1. package com.test;
  3. import java.util.ArrayList;
  4. import java.util.List;
  5. import java.util.concurrent.ConcurrentHashMap;
  7. import com.test.domain.Discount;
  8. import com.test.domain.Goods;
  9. import com.test.domain.ResponseMessage;
  10. import com.test.enums.ActivityJREnum;
  11. import com.test.strategy.IJRStrategy;
  12. import com.test.strategy.context.JRSimpleContext;
  13. import com.test.strategy.impl.LaoDongJR;
  14. import com.test.strategy.impl.QixiJR;
  15. import com.test.strategy.impl.YuanXiaoJR;
  17. public class Main {
  19.     private static JRSimpleContext jrSimpleContext;
  21.     public static void main(String[] args) {
  22.         List<Goods> goodsInfo = new ArrayList<Goods>();
  23.         Goods goods1 = new Goods("1", "玫瑰", 888.0, 1);
  24.         Goods goods2 = new Goods("2", "巧克力", 999.0, 1);
  25.         Goods goods3 = new Goods("3", "苹果", 999.0, 2);
  26.         goodsInfo.add(goods1);
  27.         goodsInfo.add(goods2);
  28.         goodsInfo.add(goods3);
  29.         // 申明折扣
  30.         Discount discount = null;
  31.         // 申明节日策略
  32.         IJRStrategy ijrStrategy = null;
  33.         // 创建返回提示内容
  34.         StringBuilder sb =new StringBuilder();
  35.         ConcurrentHashMap<Integer, IJRStrategy> concurrentHashMap = new ConcurrentHashMap<>();
  36.         for (int i = 0; i < goodsInfo.size(); i++) {
  37.             Integer sourceFlg = goodsInfo.get(i).getSourceFlg();
  38.             if ( ActivityJREnum.QIXIJIE.getCode().equals(sourceFlg)) {
  39.                 ijrStrategy = new QixiJR();
  40.             } else if (ActivityJREnum.LAODONGJIE.getCode().equals(sourceFlg)) {
  41.                 ijrStrategy = new LaoDongJR();
  42.             } else if (ActivityJREnum.YUANXIAOJIE.getCode().equals(sourceFlg)) {
  43.                 ijrStrategy = new YuanXiaoJR();
  44.             } else {
  45.                 // 不处理
  46.             }
  47.             concurrentHashMap.put(sourceFlg, ijrStrategy);
  48.             // 获取商品折扣信息
  49.             if (sourceFlg!=null) {
  50.                 discount = getDiscount(sourceFlg);
  51.             }
  52.             // 每个商品对应的折扣
  53.             goodsInfo.get(i).setDiscount(discount);
  54.         }
  55.         jrSimpleContext = new JRSimpleContext(concurrentHashMap);
  56.         List<Goods> source = jrSimpleContext.getSource(goodsInfo);
  57.         sb.append(source);
  58.         ResponseMessage rMessage = new ResponseMessage();
  59.         rMessage.setCode(200);
  60.         rMessage.setData(sb);
  61.         rMessage.setMsg("请求成功！");
  62.         System.out.println(rMessage);
  63.     }
  65.     /**
  66.      * 判断属于那个活动
  67.      * 
  68.      * @return
  69.      */
  70.     public static Discount getDiscount(Integer sourceFlg) {
  71.         Discount discount = new Discount();
  72.         // 这里还可以更加仔细的衍生下去，对单独的商品进行对应商品折扣判断
  73.         if (ActivityJREnum.QIXIJIE.getCode().equals(sourceFlg)) {
  74.             // 返回对应商品的折扣
  75.             discount.setNo(8);
  76.             discount.setMessage("八折");
  77.             discount.setJieRi("七夕节专属情侣商品特供：");
  78.         } else if (ActivityJREnum.LAODONGJIE.getCode().equals(sourceFlg)) {
  79.             discount.setNo(9);
  80.             discount.setMessage("九折");
  81.             discount.setJieRi("劳动节专属商务商品特供：");
  82.         } else if (ActivityJREnum.LAODONGJIE.getCode().equals(sourceFlg)) {
  83.             discount.setNo(7);
  84.             discount.setMessage("七折");
  85.             discount.setJieRi("元宵节专属家庭商品特供：");
  86.         } else {
  87.             // 不处理
  88.         }
  89.         return discount;
  90.     }
  91. }

执行结果

ResponseMessage [code=200, data=[Goods [no=1, name=玫瑰, price=710.4, sourceFlg=1, discount=Discount [no=8, message=八折, jieRi=七夕节专属情侣商品特供：]], Goods [no=2, name=巧克力, price=799.2, sourceFlg=1, discount=Discount [no=8, message=八折, jieRi=七夕节专属情侣商品特供：]], Goods [no=3, name=苹果, price=699.3, sourceFlg=2, discount=Discount [no=9, message=九折, jieRi=劳动节专属商务商品特供：]]], msg=请求成功！]