JAVA【设计模式】工厂方法模式

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一、定义

⼯⼚模式⼜称⼯⼚⽅法模式，是⼀种创建型设计模式，其在⽗类中提供⼀个创建对象的⽅法，允许⼦类决定实例化对象的类型。

这种设计模式也是 Java 开发中最常⻅的⼀种模式，它的主要意图是定义⼀个创建对象的接⼝，让其⼦类⾃⼰决定实例化哪⼀个⼯⼚类，⼯⼚模式使其创建过程延迟到⼦类进⾏。

简单说就是为了提供代码结构的扩展性，屏蔽每⼀个功能类中的具体实现逻辑。让外部可以更加简单的只是知道调⽤即可，同时，这也是去掉众多 ifelse 的⽅式。当然这可能也有⼀些缺点，⽐如需要实现的类⾮常多，如何去维护，怎样减低开发成本。但这些问题都可以在后续的设计模式结合使⽤中，逐步降低。

二、示例：

模拟场景： 1、例如：一般找对象的方式，是通过自己去认识到新的姑娘，类似于姑娘这个对象需要自己new出来。假设有一个红娘牵线平台，你只需要说出你的需求，想要什么样的姑娘，平台就会给你连线出怎么的姑娘。。。 2、例如：商店定义成工厂，我需要在商店里面兑换奖品，奖品的类型包括爱奇艺兑换卡、实物商品、优惠券等等，假设我想要兑换实物商品，我只要在商店里面获取实物商品对象即可，不需要关心实物商品类是怎么创建的。。。

爱奇艺卡券类：IQiYiCard


package com.qf.design.create.factorymethod.entity.card;

/**
 * @description 模拟爱奇艺视频卡，对象类
 */
public class IQiYiCard {

     // 卡券的一些信息

}

获取爱奇艺卡券类：IQiYiCardService


package com.qf.design.create.factorymethod.entity.card;

/**
 * @description 模拟爱奇艺会员卡服务
 */
public class IQiYiCardService {

    public void grantToken(String bindMobileNumber, String cardId) {
        System.out.println("模拟发放爱奇艺会员卡一张：" + bindMobileNumber + "，" + cardId);
    }

}

优惠券类：CouponInfo


package com.qf.design.create.factorymethod.entity.coupon;

/**
 * @description 模拟优惠券，对象类
 */
public class CouponInfo {

    // 优惠券的一些信息

}

获取优惠券服务: CouponService


package com.qf.design.create.factorymethod.entity.coupon;

/**
 * @description 模拟优惠券服务
 */
public class CouponService {

    public CouponResult sendCoupon(String uId, String couponNumber, String uuid) {
        System.out.println("模拟发放优惠券一张：" + uId + "," + couponNumber + "," + uuid);
        return new CouponResult("0000", "发放成功");
    }

}

优惠券返回结果类:CouponResult


package com.qf.design.create.factorymethod.entity.coupon;

/**
 * @description 优惠券返回结果类
 */
public class CouponResult {

    private String code; // 编码
    private String info; // 描述

    public CouponResult(String code, String info) {
        this.code = code;
        this.info = info;
    }

    public String getCode() {
        return code;
    }

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

    public String getInfo() {
        return info;
    }

    public void setInfo(String info) {
        this.info = info;
    }
}

商品信息：GoodsInfo


package com.qf.design.create.factorymethod.entity.goods;

/**
 * @description 模拟商品信息，对象类
 */
public class GoodsInfo {
}

获取实物商品服务：GoodsService


package com.qf.design.create.factorymethod.entity.goods;

import com.alibaba.fastjson.JSON;

/**
 * @description 模拟实物商品服务
 */
public class GoodsService {

    public Boolean deliverGoods(DeliverReq req) {
        System.out.println("模拟发货实物商品一个：" + JSON.toJSONString(req));
        return true;
    }

}

实物商品服务返回结果：DeliverReq


package com.qf.design.create.factorymethod.entity.goods;

public class DeliverReq {

    private String userName;              // 用户姓名
    private String userPhone;             // 用户手机
    private String sku;                   // 商品SKU
    private String orderId;               // 订单ID
    private String consigneeUserName;     // 收货人姓名
    private String consigneeUserPhone;    // 收货人手机
    private String consigneeUserAddress;  // 收获人地址

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getUserPhone() {
        return userPhone;
    }

    public void setUserPhone(String userPhone) {
        this.userPhone = userPhone;
    }

    public String getSku() {
        return sku;
    }

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

    public String getOrderId() {
        return orderId;
    }

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

    public String getConsigneeUserName() {
        return consigneeUserName;
    }

    public void setConsigneeUserName(String consigneeUserName) {
        this.consigneeUserName = consigneeUserName;
    }

    public String getConsigneeUserPhone() {
        return consigneeUserPhone;
    }

    public void setConsigneeUserPhone(String consigneeUserPhone) {
        this.consigneeUserPhone = consigneeUserPhone;
    }

    public String getConsigneeUserAddress() {
        return consigneeUserAddress;
    }

    public void setConsigneeUserAddress(String consigneeUserAddress) {
        this.consigneeUserAddress = consigneeUserAddress;
    }
}

传统硬编码方式(都在一个类里面实现，多重if else嵌套使用)

发奖请求对象：AwardReq


package com.qf.design.create.factorymethod.tradition;

import java.util.Map;

/**
 * @description 发奖请求对象
 */
public class AwardReq {

    private String uId;                 // 用户唯一ID
    private Integer awardType;          // 奖品类型(可以用枚举定义)；1优惠券、2实物商品、3第三方兑换卡(爱奇艺)
    private String awardNumber;         // 奖品编号；sku、couponNumber、cardId
    private String bizId;               // 业务ID，防重复
    private Map<String, String> extMap; // 扩展信息

    public String getuId() {
        return uId;
    }

    public void setuId(String uId) {
        this.uId = uId;
    }

    public Integer getAwardType() {
        return awardType;
    }

    public void setAwardType(Integer awardType) {
        this.awardType = awardType;
    }

    public String getAwardNumber() {
        return awardNumber;
    }

    public void setAwardNumber(String awardNumber) {
        this.awardNumber = awardNumber;
    }

    public String getBizId() {
        return bizId;
    }

    public void setBizId(String bizId) {
        this.bizId = bizId;
    }

    public Map<String, String> getExtMap() {
        return extMap;
    }

    public void setExtMap(Map<String, String> extMap) {
        this.extMap = extMap;
    }
}

发奖结果反馈对象：AwardRes


package com.qf.design.create.factorymethod.tradition;

/**
 * @description 发奖结果反馈对象
 */
public class AwardRes {

    private String code; // 编码
    private String info; // 描述

    public AwardRes(String code, String info) {
        this.code = code;
        this.info = info;
    }

    public String getCode() {
        return code;
    }

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

    public String getInfo() {
        return info;
    }

    public void setInfo(String info) {
        this.info = info;
    }

}

模拟发奖服务：PrizeController ,多重语句if else判断，代码功能实现了，但是不好后续的维护和扩展


package com.qf.design.create.factorymethod.tradition;

import com.alibaba.fastjson.JSON;
import com.qf.design.create.factorymethod.entity.card.IQiYiCardService;
import com.qf.design.create.factorymethod.entity.coupon.CouponResult;
import com.qf.design.create.factorymethod.entity.coupon.CouponService;
import com.qf.design.create.factorymethod.entity.goods.DeliverReq;
import com.qf.design.create.factorymethod.entity.goods.GoodsService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * @description 模拟发奖服务
 */
public class PrizeController {

    private Logger logger = LoggerFactory.getLogger(PrizeController.class);

    public AwardRes awardToUser(AwardReq req) {
        String reqJson = JSON.toJSONString(req);
        AwardRes awardRes = null;
        try {
            logger.info("奖品发放开始{}。req:{}", req.getuId(), reqJson);
            // 按照不同类型方法商品[1优惠券、2实物商品、3第三方兑换卡(爱奇艺)]
            if (req.getAwardType() == 1) {
                CouponService couponService = new CouponService();
                CouponResult couponResult = couponService.sendCoupon(req.getuId(), req.getAwardNumber(), req.getBizId());
                if ("0000".equals(couponResult.getCode())) {
                    awardRes = new AwardRes("0000", "发放成功");
                } else {
                    awardRes = new AwardRes("0001", couponResult.getInfo());
                }
            } else if (req.getAwardType() == 2) {
                GoodsService goodsService = new GoodsService();
                DeliverReq deliverReq = new DeliverReq();
                deliverReq.setUserName(queryUserName(req.getuId()));
                deliverReq.setUserPhone(queryUserPhoneNumber(req.getuId()));
                deliverReq.setSku(req.getAwardNumber());
                deliverReq.setOrderId(req.getBizId());
                deliverReq.setConsigneeUserName(req.getExtMap().get("consigneeUserName"));
                deliverReq.setConsigneeUserPhone(req.getExtMap().get("consigneeUserPhone"));
                deliverReq.setConsigneeUserAddress(req.getExtMap().get("consigneeUserAddress"));
                Boolean isSuccess = goodsService.deliverGoods(deliverReq);
                if (isSuccess) {
                    awardRes = new AwardRes("0000", "发放成功");
                } else {
                    awardRes = new AwardRes("0001", "发放失败");
                }
            } else if (req.getAwardType() == 3) {
                String bindMobileNumber = queryUserPhoneNumber(req.getuId());
                IQiYiCardService iQiYiCardService = new IQiYiCardService();
                iQiYiCardService.grantToken(bindMobileNumber, req.getAwardNumber());
                awardRes = new AwardRes("0000", "发放成功");
            }
            logger.info("奖品发放完成{}。", req.getuId());
        } catch (Exception e) {
            logger.error("奖品发放失败{}。req:{}", req.getuId(), reqJson, e);
            awardRes = new AwardRes("0001", e.getMessage());
        }

        return awardRes;
    }

    private String queryUserName(String uId) {
        return "花花";
    }

    private String queryUserPhoneNumber(String uId) {
        return "15200101232";
    }

}

测试：ApiTest


package com.qf.design.create.factorymethod.tradition;

import com.alibaba.fastjson.JSON;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.HashMap;

public class ApiTest {
    private static Logger logger = LoggerFactory.getLogger(ApiTest.class);
    public static void main(String[] args) {
        PrizeController prizeController = new PrizeController();

        System.out.println("\\\\r\\\\n模拟发放优惠券测试\\\\r\\\\n");
        // 模拟发放优惠券测试
        AwardReq req01 = new AwardReq();
        req01.setuId("10001");
        req01.setAwardType(1);
        req01.setAwardNumber("EGM1023938910232121323432");
        req01.setBizId("791098764902132");
        AwardRes awardRes01 = prizeController.awardToUser(req01);

        logger.info("请求参数：{}", JSON.toJSON(req01));
        logger.info("测试结果：{}", JSON.toJSON(awardRes01));

        System.out.println("\\\\r\\\\n模拟方法实物商品\\\\r\\\\n");
        // 模拟方法实物商品
        AwardReq req02 = new AwardReq();
        req02.setuId("10001");
        req02.setAwardType(2);
        req02.setAwardNumber("9820198721311");
        req02.setBizId("1023000020112221113");
        req02.setExtMap(new HashMap<String, String>() {{
            put("consigneeUserName", "谢飞机");
            put("consigneeUserPhone", "15200292123");
            put("consigneeUserAddress", "吉林省.长春市.双阳区.XX街道.檀溪苑小区.#18-2109");
        }});

        AwardRes awardRes02 = prizeController.awardToUser(req02);
        logger.info("请求参数：{}", JSON.toJSON(req02));
        logger.info("测试结果：{}", JSON.toJSON(awardRes02));

        System.out.println("\\\\r\\\\n第三方兑换卡(爱奇艺)\\\\r\\\\n");
        AwardReq req03 = new AwardReq();
        req03.setuId("10001");
        req03.setAwardType(3);
        req03.setAwardNumber("AQY1xjkUodl8LO975GdfrYUio");

        AwardRes awardRes03 = prizeController.awardToUser(req03);
        logger.info("请求参数：{}", JSON.toJSON(req03));
        logger.info("测试结果：{}", JSON.toJSON(awardRes03));
    }
}

工厂方法模式设计

定义一个奖品的接口：ICommodity ，所有的奖品都实现此接口


package com.qf.design.create.factorymethod.design;

import java.util.Map;

/**
 * 发送奖品接口
 */
public interface ICommodity {
    /**
     *     private String uId;                 // 用户唯一ID
     *     private Integer awardType;          // 奖品类型(可以用枚举定义)；1优惠券、2实物商品、3第三方兑换卡(爱奇艺)
     *     private String awardNumber;         // 奖品编号；sku、couponNumber、cardId
     *     private String bizId;               // 业务ID，防重复
     *     private Map<String, String> extMap; // 扩展信息
     * @param uId
     * @param awardNumber
     * @param bizId
     * @param extMap
     */
    void sendCommodity(String uId, String commodityId, String awardNumber, String bizId, Map<String, String> extMap);
}

爱奇艺卡片：CardCommodityService


package com.qf.design.create.factorymethod.design;

import com.alibaba.fastjson.JSON;
import com.qf.design.create.factorymethod.entity.card.IQiYiCardService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.Map;

public class CardCommodityService implements ICommodity {

    private Logger logger = LoggerFactory.getLogger(CardCommodityService.class);

    // 模拟注入
    private IQiYiCardService iQiYiCardService = new IQiYiCardService();

    @Override
    public void sendCommodity(String uId, String commodityId, String awardNumber, String bizId, Map<String, String> extMap) {
        String mobile = queryUserMobile(uId);
        iQiYiCardService.grantToken(mobile, bizId);
        logger.info("请求参数[爱奇艺兑换卡] => uId：{} commodityId：{} bizId：{} extMap：{}", uId, commodityId, bizId, JSON.toJSON(extMap));
        logger.info("测试结果[爱奇艺兑换卡]：success");
    }

    private String queryUserMobile(String uId) {
        return "15200101232";
    }
}

优惠卷：CouponCommodityService


package com.qf.design.create.factorymethod.design;

import com.alibaba.fastjson.JSON;
import com.qf.design.create.factorymethod.entity.coupon.CouponResult;
import com.qf.design.create.factorymethod.entity.coupon.CouponService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.Map;

public class CouponCommodityService implements ICommodity  {

    private Logger logger = LoggerFactory.getLogger(CouponCommodityService.class);

    private CouponService couponService = new CouponService();

    @Override
    public void sendCommodity(String uId, String commodityId, String awardNumber, String bizId, Map<String, String> extMap) {
        CouponResult couponResult = couponService.sendCoupon(uId, commodityId, bizId);
        logger.info("请求参数[优惠券] => uId：{} commodityId：{} bizId：{} extMap：{}", uId, commodityId, bizId, JSON.toJSON(extMap));
        logger.info("测试结果[优惠券]：{}", JSON.toJSON(couponResult));
        if (!"0000".equals(couponResult.getCode())) throw new RuntimeException(couponResult.getInfo());
    }
}

商品实体：GoodsCommodityService


package com.qf.design.create.factorymethod.design;

import com.alibaba.fastjson.JSON;
import com.qf.design.create.factorymethod.entity.goods.DeliverReq;
import com.qf.design.create.factorymethod.entity.goods.GoodsService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.Map;

public class GoodsCommodityService implements ICommodity  {

    private Logger logger = LoggerFactory.getLogger(CouponCommodityService.class);

    private GoodsService goodsService = new GoodsService();

    @Override
    public void sendCommodity(String uId, String commodityId, String awardNumber, String bizId, Map<String, String> extMap) {
        DeliverReq deliverReq = new DeliverReq();
        deliverReq.setUserName(queryUserName(uId));
        deliverReq.setUserPhone(queryUserPhoneNumber(uId));
        deliverReq.setSku(commodityId);
        deliverReq.setOrderId(bizId);
        deliverReq.setConsigneeUserName(extMap.get("consigneeUserName"));
        deliverReq.setConsigneeUserPhone(extMap.get("consigneeUserPhone"));
        deliverReq.setConsigneeUserAddress(extMap.get("consigneeUserAddress"));

        Boolean isSuccess = goodsService.deliverGoods(deliverReq);

        logger.info("请求参数[实物商品] => uId：{} commodityId：{} bizId：{} extMap：{}", uId, commodityId, bizId, JSON.toJSON(extMap));
        logger.info("测试结果[实物商品]：{}", isSuccess);

        if (!isSuccess) throw new RuntimeException("实物商品发放失败");
    }

    private String queryUserName(String uId) {
        return "花花";
    }

    private String queryUserPhoneNumber(String uId) {
        return "15200101232";
    }
}

商店，工厂：StoreFactory


package com.qf.design.create.factorymethod.design;

import com.qf.design.create.factorymethod.entity.card.IQiYiCardService;

/**
 * 实例化工厂
 */
public class StoreFactory {

    public ICommodity getCommodityService(int type){
        switch (type){
            case 1:
                return new CouponCommodityService();
            case 2:
                return new GoodsCommodityService();
            case 3:
                return new CardCommodityService();
        }
        throw new RuntimeException("不存在的奖品服务类型");
    }

    public ICommodity getCommodityClass(Class<?  extends ICommodity> clazz) throws IllegalAccessException, InstantiationException {
        if (clazz==null)return null;
        return  clazz.newInstance();
    }
}

测试：ApiTest


package com.qf.design.create.factorymethod.design;

import org.junit.jupiter.api.Test;

import java.util.HashMap;

public class ApiTest {

    @Test
    public void test_StoreFactory_01() throws Exception {
        StoreFactory storeFactory = new StoreFactory();

        // 1. 优惠券
        ICommodity commodityService_1 = storeFactory.getCommodityService(1);
        commodityService_1.sendCommodity("10001", "EGM1023938910232121323432", null, "791098764902132",null);

        // 2. 实物商品
        ICommodity commodityService_2 = storeFactory.getCommodityService(2);
        commodityService_2.sendCommodity("10001", "9820198721311", null, null,new HashMap<String, String>() {{
            put("consigneeUserName", "谢飞机");
            put("consigneeUserPhone", "15200292123");
            put("consigneeUserAddress", "吉林省.长春市.双阳区.XX街道.檀溪苑小区.#18-2109");
        }});

        // 3. 第三方兑换卡(模拟爱奇艺)
        ICommodity commodityService_3 = storeFactory.getCommodityService(3);
        commodityService_3.sendCommodity("10001", "AQY1xjkUodl8LO975GdfrYUio", null, null,null);

    }

    @Test
    public void test_StoreFactory_02() throws Exception {
        StoreFactory storeFactory = new StoreFactory();
        // 1. 优惠券
        ICommodity commodityService = storeFactory.getCommodityClass(CouponCommodityService.class);
        commodityService.sendCommodity("10001", "EGM1023938910232121323432", "791098764902132", null,null);

        // 2. 实物商品
        ICommodity commodityService_2 = storeFactory.getCommodityClass(GoodsCommodityService.class);
        commodityService_2.sendCommodity("10001", "9820198721311", null, null,new HashMap<String, String>() {{
            put("consigneeUserName", "谢飞机");
            put("consigneeUserPhone", "15200292123");
            put("consigneeUserAddress", "吉林省.长春市.双阳区.XX街道.檀溪苑小区.#18-2109");
        }});

        // 3. 第三方兑换卡(模拟爱奇艺)
        ICommodity commodityService_3 = storeFactory.getCommodityClass(CardCommodityService.class);
        commodityService_3.sendCommodity("10001", "AQY1xjkUodl8LO975GdfrYUio", null, null,null);
    }
}

总结：避免创建者与具体的产品逻辑耦合 、满⾜单⼀职责，每⼀个业务逻辑实现都在所属⾃⼰的类中完成、满⾜开闭原则，⽆需更改使⽤调⽤⽅就可以在程序中引⼊新的产品类型 。但这样也会带来⼀些问题，⽐如有⾮常多的奖品类型，那么实现的⼦类会极速扩张。因此也需要使⽤其他的模式进⾏优化，这些在后续的设计模式中会逐步涉及到