问题：通过策略模式+工厂模式+模板方法模式实现ifelse优化

项目场景：

提示：这里简述项目相关背景：

示例：商城系统有会员系统，不同会员有不同优惠程度，普通会员不优惠；黄金会员打8折；白金会员优惠50元，再打7折；

问题描述

提示：这里描述项目中遇到的问题：

例如：不同会员处理过程中，业务场景复杂，每种会员的业务逻辑很长，不方便维护。

public static double quote(String type) {double score = 1000;double res = 0;if (type.equals("1")) {res = score;} else if (type.equals("2")) {res = score - 50;} else if (type.equals("3")) {res = score * 0.8;} else if (type.equals("4")) {res = (score - 50) * 0.7;}return res;}

原因分析：

提示：这里填写问题的分析：

业务复杂

解决方案：

在这里插入图片描述

提示：这里填写该问题的具体解决方案：

package com.geekmice.springbootmybatiscrud.strategy.third;import java.math.BigDecimal;public interface PayStrategy {/*** 计算费用** @param price* @date 2025-02-10*/BigDecimal quote(BigDecimal price);
}

具体策略1:非会员，没有优惠

package com.geekmice.springbootmybatiscrud.strategy.third;import java.math.BigDecimal;public class OrdinaryStrategy implements PayStrategy{@Overridepublic BigDecimal quote(BigDecimal price) {return price;}
}

具体策略2：黄金会员，打八折

package com.geekmice.springbootmybatiscrud.strategy.third;import java.math.BigDecimal;
import java.util.Objects;public class GoldStrategy implements PayStrategy{@Overridepublic BigDecimal quote(BigDecimal price) {BigDecimal res = price.multiply(new BigDecimal("0.8"));return res;}
}

具体策略3：白银会员，先优惠50，后打七折

package com.geekmice.springbootmybatiscrud.strategy.third;import com.geekmice.springbootmybatiscrud.strategy.first.Strategy;import java.math.BigDecimal;public class PlatinumStrategy implements PayStrategy {@Overridepublic BigDecimal quote(BigDecimal price) {BigDecimal res = price.subtract(new BigDecimal("50")).multiply(new BigDecimal("0.7"));return res;}
}

上下文对象:持有一个Strategy的引用

package com.geekmice.springbootmybatiscrud.strategy.third;import java.math.BigDecimal;/*** @author Administrator*/
public class PayContext {private PayStrategy payStrategy;public void setStrategy(PayStrategy payStrategy) {this.payStrategy = payStrategy;}public BigDecimal getPrice(BigDecimal price) {if (payStrategy != null) {return payStrategy.quote(price);}return null;}
}

测试使用

package com.geekmice.springbootmybatiscrud.strategy.third;import java.math.BigDecimal;public class Demo {public static void main(String[] args) {PayContext payContext = new PayContext();OrdinaryStrategy ordinaryStrategy = new OrdinaryStrategy();payContext.setStrategy(ordinaryStrategy);System.out.println("普通会员："+payContext.getPrice(new BigDecimal("100")));GoldStrategy goldStrategy = new GoldStrategy();payContext.setStrategy(goldStrategy);System.out.println("黄金会员："+payContext.getPrice(new BigDecimal("100")));PlatinumStrategy platinumStrategy = new PlatinumStrategy();payContext.setStrategy(platinumStrategy);System.out.println("白银会员："+payContext.getPrice(new BigDecimal("100")));}
}

结果

普通会员：100
黄金会员：80.0
白银会员：35.0

优化1：新增其他策略，不影响现有的策略

思路：新增策略类，实现策略接口

package com.geekmice.springbootmybatiscrud.strategy.third;import java.math.BigDecimal;public class SilverStrategy implements PayStrategy{@Overridepublic BigDecimal quote(BigDecimal price) {return price.subtract(new BigDecimal("50"));}
}package com.geekmice.springbootmybatiscrud.strategy.third;import java.math.BigDecimal;public class Demo {public static void main(String[] args) {PayContext payContext = new PayContext();OrdinaryStrategy ordinaryStrategy = new OrdinaryStrategy();payContext.setStrategy(ordinaryStrategy);System.out.println("普通会员："+payContext.getPrice(new BigDecimal("100")));GoldStrategy goldStrategy = new GoldStrategy();payContext.setStrategy(goldStrategy);System.out.println("黄金会员："+payContext.getPrice(new BigDecimal("100")));PlatinumStrategy platinumStrategy = new PlatinumStrategy();payContext.setStrategy(platinumStrategy);System.out.println("白银会员："+payContext.getPrice(new BigDecimal("100")));SilverStrategy silverStrategy = new SilverStrategy();payContext.setStrategy(silverStrategy);System.out.println("白金会员："+payContext.getPrice(new BigDecimal("100")));}
}

普通会员：100
黄金会员：80.0
白银会员：35.0
白金会员：50

优化2：策略中出现相同逻辑，如何处理

说明：策略2与策略3处理逻辑中都有需要处理的内容，这个内容可能很长，初始化参数，或者校验参数，远程调用获取数据等操作，都是类似的逻辑，可以抽取到抽象类中，子类需要哪个实现哪个方法，重复的直接在父类操作。

在这里插入图片描述

策略工厂

package com.geekmice.springbootmybatiscrud.strategy.fifth;import java.util.HashMap;
import java.util.Map;
import java.util.Objects;
/*** @author mbp* @date 2025-02-11*/
public class StrategyFactory {/*** 设置策略map*/private static Map<String, Strategy> strategyMap = new HashMap<>(16);public static Strategy getStrategyService(String type) {return strategyMap.get(type);}/*** 提前策略装入 strategyMap*/public static void register(String type, Strategy strategy) {if (Objects.isNull(type)) {return;}strategyMap.put(type, strategy);}
}

策略接口

package com.geekmice.springbootmybatiscrud.strategy.fifth;import org.springframework.beans.factory.InitializingBean;import java.math.BigDecimal;
/*** @author mbp* @date 2025-02-11*/
public interface Strategy extends InitializingBean {BigDecimal quote(BigDecimal price);}

模板方式抽象类

package com.geekmice.springbootmybatiscrud.strategy.fifth;/*** @author mbp* @date 2025-02-11*/
public abstract class BaseMember {/*** 需要父类执行关键重复逻辑*/protected void exec(){System.out.println("处理内容");}}

具体策略1

package com.geekmice.springbootmybatiscrud.strategy.fifth;import org.springframework.stereotype.Component;import java.math.BigDecimal;
/*** @author mbp* @date 2025-02-11*/
@Component
public class OrdinaryStrategy extends BaseMember  implements Strategy {@Overridepublic BigDecimal quote(BigDecimal price) {this.exec();return price;}@Overridepublic void afterPropertiesSet() throws Exception {StrategyFactory.register("1",this);}
}

具体策略2

package com.geekmice.springbootmybatiscrud.strategy.fifth;import org.springframework.stereotype.Component;import java.math.BigDecimal;
/*** @author mbp* @date 2025-02-11*/
@Component
public class GoldStrategy extends BaseMember implements Strategy {@Overridepublic BigDecimal quote(BigDecimal price) {BigDecimal res = price.multiply(new BigDecimal("0.8"));this.exec();return res;}@Overridepublic void afterPropertiesSet() throws Exception {StrategyFactory.register("2", this);}}

具体策略3

package com.geekmice.springbootmybatiscrud.strategy.fifth;import org.springframework.stereotype.Component;import java.math.BigDecimal;
/*** @author mbp* @date 2025-02-11*/
@Component
public class PlatinumStrategy extends BaseMember implements Strategy {@Overridepublic BigDecimal quote(BigDecimal price) {BigDecimal res = price.subtract(new BigDecimal("50")).multiply(new BigDecimal("0.7"));return res;}@Overridepublic void afterPropertiesSet() throws Exception {StrategyFactory.register("3", this);}
}

测试类

package com.geekmice.springbootmybatiscrud.controller;import com.geekmice.springbootmybatiscrud.dao.StudentMapper;
import com.geekmice.springbootmybatiscrud.pojo.Student;
import com.geekmice.springbootmybatiscrud.strategy.fifth.Strategy;
import com.geekmice.springbootmybatiscrud.strategy.fifth.StrategyFactory;
import org.springframework.web.bind.annotation.*;import javax.annotation.Resource;
import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.List;/*** @author Administrator*/
@RestController
@RequestMapping("/student")
public class StudentController {@Resourceprivate StudentMapper studentMapper;@GetMapping(value = "queryAll")public List<Student> queryAll() {Strategy strategyService = StrategyFactory.getStrategyService("1");System.out.println(strategyService.quote(new BigDecimal("1000")));Strategy strategyService2 = StrategyFactory.getStrategyService("2");System.out.println(strategyService2.quote(new BigDecimal("1000")));Strategy strategyService1 = StrategyFactory.getStrategyService("3");System.out.println(strategyService1.quote(new BigDecimal("1000")));return new ArrayList<>();}}

优化3：传递策略类型

根据某个策略类型，执行某个策略逻辑

思路：需要保证某个类型对应某个策略类，通过spring中InitializingBean接口初始化bean，项目启动过程执行实现InitializingBean接口中的afterPropertiesSet方法，在这个方法中初始化map中指定的策略。

策略接口

public interface Strategy extends InitializingBean {BigDecimal quote(BigDecimal price);
}

策略工厂

package com.geekmice.springbootmybatiscrud.strategy.fourth;import org.springframework.stereotype.Component;import java.util.HashMap;
import java.util.Map;
import java.util.Objects;public class StrategyFactory {/*** 设置策略map*/private static Map<String, Strategy> strategyMap = new HashMap<>(16);public static Strategy getStrategyService(String type) {return strategyMap.get(type);}/*** 提前策略装入 strategyMap*/public static void register(String type, Strategy strategy) {if (Objects.isNull(type)) {return;}strategyMap.put(type, strategy);}
}

具体策略1

package com.geekmice.springbootmybatiscrud.strategy.fourth;import com.geekmice.springbootmybatiscrud.strategy.third.PayStrategy;
import org.springframework.stereotype.Component;import java.math.BigDecimal;
@Component
public class OrdinaryStrategy implements Strategy {@Overridepublic BigDecimal quote(BigDecimal price) {
//        System.out.println("都要处理的内容");return price;}@Overridepublic void afterPropertiesSet() throws Exception {System.out.println("11111111111");StrategyFactory.register("1",this);}
}

具体策略2

package com.geekmice.springbootmybatiscrud.strategy.fourth;import com.geekmice.springbootmybatiscrud.strategy.third.PayStrategy;
import org.springframework.stereotype.Component;import java.math.BigDecimal;
@Component
public class GoldStrategy implements Strategy {@Overridepublic BigDecimal quote(BigDecimal price) {BigDecimal res = price.multiply(new BigDecimal("0.8"));return res;}@Overridepublic void afterPropertiesSet() throws Exception {System.out.println("222222222222");StrategyFactory.register("2",this);}
}

具体策略3

package com.geekmice.springbootmybatiscrud.strategy.fourth;import com.geekmice.springbootmybatiscrud.strategy.third.PayStrategy;
import org.springframework.stereotype.Component;import java.math.BigDecimal;
@Component
public class PlatinumStrategy implements Strategy {@Overridepublic BigDecimal quote(BigDecimal price) {// 都要处理的内容// System.out.println("都要处理的内容");BigDecimal res = price.subtract(new BigDecimal("50")).multiply(new BigDecimal("0.7"));return res;}@Overridepublic void afterPropertiesSet() throws Exception {System.out.println("3333333333333");StrategyFactory.register("3",this);}}

测试

package com.geekmice.springbootmybatiscrud.controller;import com.geekmice.springbootmybatiscrud.dao.StudentMapper;
import com.geekmice.springbootmybatiscrud.pojo.Student;
import com.geekmice.springbootmybatiscrud.strategy.first.StrategyFactory;
import com.geekmice.springbootmybatiscrud.strategy.fourth.Strategy;
import org.springframework.web.bind.annotation.*;import javax.annotation.Resource;
import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.List;/*** @author Administrator*/
@RestController
@RequestMapping("/student")
public class StudentController {@Resourceprivate StudentMapper studentMapper;@GetMapping(value = "queryAll")public List<Student> queryAll() {Strategy strategyService =StrategyFactory.getStrategyService("1");System.out.println(strategyService);System.out.println(strategyService.quote(new BigDecimal("1000")));return new ArrayList<>();}}