裝飾器模式-實現電商的優惠活動價格計算

1、案例

1、商品有基本價格
2、可以使用優惠券和紅包兩種優惠活動
3、基於裝飾器模式，實現價格的計算和擴展。

2、實現代碼-業務邏輯

2.1、商品類

import java.math.BigDecimal;
import java.util.Map;

/**
 * 商品實體類
 */
public class Merchandise {
    private String sku;
    private String name;
    private BigDecimal price;
    private Map<PromotionType, SupportPromotions> supportPromotions;

    public String getSku() {
        return sku;
    }

    public void setSku(String sku) {
        this.sku = sku;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public BigDecimal getPrice() {
        return price;
    }

    public void setPrice(BigDecimal price) {
        this.price = price;
    }

    public Map<PromotionType, SupportPromotions> getSupportPromotions() {
        return supportPromotions;
    }

    public void setSupportPromotions(Map<PromotionType, SupportPromotions> supportPromotions) {
        this.supportPromotions = supportPromotions;
    }
}

2.2、訂單類

import java.math.BigDecimal;
import java.util.List;

/**
 * 訂單實體類
 */
public class Order {
    private int id;
    private String orderNo;
    private BigDecimal totalPayMoney;
    private List<OrderDetail> list;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getOrderNo() {
        return orderNo;
    }

    public void setOrderNo(String orderNo) {
        this.orderNo = orderNo;
    }

    public BigDecimal getTotalPayMoney() {
        return totalPayMoney;
    }

    public void setTotalPayMoney(BigDecimal totalPayMoney) {
        this.totalPayMoney = totalPayMoney;
    }

    public List<OrderDetail> getList() {
        return list;
    }

    public void setList(List<OrderDetail> list) {
        this.list = list;
    }
}

2.3、訂單明細類

import java.math.BigDecimal;

/**
 * 訂單明細類
 */
public class OrderDetail {
    private int id;
    private int orderId;
    private Merchandise merchandise;
    private BigDecimal payMoney;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public int getOrderId() {
        return orderId;
    }

    public void setOrderId(int orderId) {
        this.orderId = orderId;
    }

    public Merchandise getMerchandise() {
        return merchandise;
    }

    public void setMerchandise(Merchandise merchandise) {
        this.merchandise = merchandise;
    }

    public BigDecimal getPayMoney() {
        return payMoney;
    }

    public void setPayMoney(BigDecimal payMoney) {
        this.payMoney = payMoney;
    }
}

2.4、優惠活動類型

/**
 * 優惠活動枚舉
 */
public enum PromotionType {
    COUPON(1),
    REDPACKET(2),
    ;
    private int code;

    PromotionType(final int code){
        this.code = code;
    }

    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }
}

2.5 優惠券類

import java.math.BigDecimal;

/**
 * 用戶優惠券類
 */
public class UserCoupon {
    private int id;
    private int userId;
    private String sku;
    private BigDecimal coupon;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public int getUserId() {
        return userId;
    }

    public void setUserId(int userId) {
        this.userId = userId;
    }

    public String getSku() {
        return sku;
    }

    public void setSku(String sku) {
        this.sku = sku;
    }

    public BigDecimal getCoupon() {
        return coupon;
    }

    public void setCoupon(BigDecimal coupon) {
        this.coupon = coupon;
    }
}

2.6 紅包類

import java.math.BigDecimal;

/**
 * 用戶紅包類
 */
public class UserRedPacket {
    private int id;
    private int userId;
    private String sku;
    private BigDecimal redPacket;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public int getUserId() {
        return userId;
    }

    public void setUserId(int userId) {
        this.userId = userId;
    }

    public String getSku() {
        return sku;
    }

    public void setSku(String sku) {
        this.sku = sku;
    }

    public BigDecimal getRedPacket() {
        return redPacket;
    }

    public void setRedPacket(BigDecimal redPacket) {
        this.redPacket = redPacket;
    }
}

2.7、商品支持的優惠活動類型

/**
 * 商品支持的優惠活動，依次計算價格
 */
public class SupportPromotions implements Cloneable {
    private int id;
    private PromotionType promotionType;
    private int priority;
    private UserCoupon userCoupon;
    private UserRedPacket userRedPacket;

    public SupportPromotions clone(){
        SupportPromotions supportPromotions = null;
        try {
            supportPromotions = (SupportPromotions) super.clone();
        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
        }

        return supportPromotions;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public PromotionType getPromotionType() {
        return promotionType;
    }

    public void setPromotionType(PromotionType promotionType) {
        this.promotionType = promotionType;
    }

    public int getPriority() {
        return priority;
    }

    public void setPriority(int priority) {
        this.priority = priority;
    }

    public UserCoupon getUserCoupon() {
        return userCoupon;
    }

    public void setUserCoupon(UserCoupon userCoupon) {
        this.userCoupon = userCoupon;
    }

    public UserRedPacket getUserRedPacket() {
        return userRedPacket;
    }

    public void setUserRedPacket(UserRedPacket userRedPacket) {
        this.userRedPacket = userRedPacket;
    }
}

3、實現代碼-裝飾器

3.1、基本接口類

import java.math.BigDecimal;

/**
 * 基本接口類
 */
public interface IBaseCount {
    /**
     * 計算訂單商品支付金額
     */
    BigDecimal countPayMoney(OrderDetail orderDetail);
}

3.2、基本實現類

import java.math.BigDecimal;

/**
 * 基本實現類
 */
public class BaseCount implements IBaseCount {
    @Override
    public BigDecimal countPayMoney(OrderDetail orderDetail) {
        orderDetail.setPayMoney(orderDetail.getMerchandise().getPrice());
        System.out.println("商品原單價金額爲：" + orderDetail.getPayMoney());

        return orderDetail.getPayMoney();
    }
}

3.3、裝飾器-基本抽象類

import java.math.BigDecimal;

/**
 * 裝飾器-基本抽象類
 */
public abstract class BaseCountDecorator implements IBaseCount {
    private IBaseCount count;

    public BaseCountDecorator(IBaseCount count) {
        this.count = count;
    }

    public BigDecimal countPayMoney(OrderDetail orderDetail) {
        BigDecimal payTotalMoney = new BigDecimal(0);
        if(count != null) {
            payTotalMoney = count.countPayMoney(orderDetail);
        }

        return payTotalMoney;
    }
}

3.4、裝飾器-優惠券類

import java.math.BigDecimal;

/**
 * 裝飾器-優惠券實現類
 */
public class CouponDecorator extends BaseCountDecorator {

    public CouponDecorator(IBaseCount count) {
        super(count);
    }

    public BigDecimal countPayMoney(OrderDetail orderDetail){
        BigDecimal payTotalMoney = new BigDecimal(0);

        payTotalMoney = super.countPayMoney(orderDetail);
        payTotalMoney = countCouponPayMoney(orderDetail);

        return payTotalMoney;
    }

    private BigDecimal countCouponPayMoney(OrderDetail orderDetail) {
        BigDecimal coupon = orderDetail.getMerchandise().getSupportPromotions().get(PromotionType.COUPON).getUserCoupon().getCoupon();
        System.out.println("優惠券金額：" + coupon);
        orderDetail.setPayMoney(orderDetail.getPayMoney().subtract(coupon));

        return orderDetail.getPayMoney();
    }
}

3.4、裝飾器-紅包類

import java.math.BigDecimal;

/**
 * 裝飾器-優惠券實現類
 */
public class RedPacketDecorator extends BaseCountDecorator {

    public RedPacketDecorator(IBaseCount count) {
        super(count);
    }

    public BigDecimal countPayMoney(OrderDetail orderDetail){
        BigDecimal payTotalMoney = new BigDecimal(0);

        payTotalMoney = super.countPayMoney(orderDetail);
        payTotalMoney = countCouponPayMoney(orderDetail);

        return payTotalMoney;
    }

    private BigDecimal countCouponPayMoney(OrderDetail orderDetail) {
        BigDecimal redPacket = orderDetail.getMerchandise().getSupportPromotions().get(PromotionType.REDPACKET).getUserRedPacket().getRedPacket();
        System.out.println("紅包優惠金額：" + redPacket);
        orderDetail.setPayMoney(orderDetail.getPayMoney().subtract(redPacket));

        return orderDetail.getPayMoney();
    }
}

3.5、優惠活動工廠計算類

import java.math.BigDecimal;
import java.util.Map;

/**
 * 優惠活動價格計算工具類
 */
public class PromotionFactory {
    public static BigDecimal getPayMoney(OrderDetail orderDetail) {
        Map<PromotionType, SupportPromotions> supportPromotionslist = orderDetail.getMerchandise().getSupportPromotions();

        IBaseCount baseCount = new BaseCount();

        if(supportPromotionslist != null) {
            for(PromotionType type : supportPromotionslist.keySet()) {
                baseCount = protmotion(supportPromotionslist.get(type), baseCount);
            }
        }

        return baseCount.countPayMoney(orderDetail);
    }

    private static IBaseCount protmotion(SupportPromotions supportPromotions, IBaseCount baseCount){
        if(supportPromotions.getPromotionType() == PromotionType.COUPON) {
            baseCount = new CouponDecorator(baseCount);
        }
        if(supportPromotions.getPromotionType() == PromotionType.COUPON) {
            baseCount = new RedPacketDecorator(baseCount);
        }

        return baseCount;
    }
}

4、啓動類

import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Main {

    public static void main(String[] args) {

        Order order = new Order();
        init(order);
        for(OrderDetail orderDetail : order.getList()){
            BigDecimal payMoney = PromotionFactory.getPayMoney(orderDetail);
            orderDetail.setPayMoney(payMoney);
            System.out.println("最終支付金額：" +  orderDetail.getPayMoney());
        }
    }

    /**
     *初始化訂單
     */
    private static Order init(Order order) {
        Map<PromotionType, SupportPromotions> supportPromotionslist = new HashMap<PromotionType, SupportPromotions>();

        SupportPromotions supportPromotions = new SupportPromotions();
        supportPromotions.setPromotionType(PromotionType.COUPON);
        supportPromotions.setPriority(1);

        UserCoupon userCoupon= new UserCoupon();
        userCoupon.setCoupon(new BigDecimal(3));
        userCoupon.setSku("aaa1111");
        userCoupon.setUserId(11);

        supportPromotions.setUserCoupon(userCoupon);

        supportPromotionslist.put(PromotionType.COUPON, supportPromotions);
        SupportPromotions supportPromotions1 = supportPromotions.clone();

        supportPromotions1.setPromotionType(PromotionType.REDPACKET);
        supportPromotions1.setPriority(2);

        UserRedPacket userRedPacket= new UserRedPacket();
        userRedPacket.setId(1);
        userRedPacket.setRedPacket(new BigDecimal(10));
        userRedPacket.setSku("aaa1111");
        userCoupon.setUserId(11);

        supportPromotions1.setUserRedPacket(userRedPacket);
        supportPromotionslist.put(PromotionType.REDPACKET, supportPromotions1);

        Merchandise merchandise = new Merchandise();
        merchandise.setSku("aaa1111");
        merchandise.setName("蘋果");
        merchandise.setPrice(new BigDecimal(20));
        merchandise.setSupportPromotions(supportPromotionslist);

        List<OrderDetail> OrderDetailList = new ArrayList<OrderDetail>();

        OrderDetail orderDetail = new OrderDetail();
        orderDetail.setId(1);
        orderDetail.setOrderId(1111);
        orderDetail.setMerchandise(merchandise);

        OrderDetailList.add(orderDetail);

        order.setList(OrderDetailList);

        return order;

    }
}

5、結果：