在之前的文章中，曾经给大家介绍过策略模式：【设计模式】策略模式，在该篇文章中，我们曾很清楚的说到，策略模式主要解决的问题是：在有多种算法相似的情况下，解决使用 if...else 所带来的复杂和难以维护。策略模式使我们的实现更加符合开闭原则：面向扩展开发，面向修改关闭。在后来的学习和工作的多次应用中，有了更加深刻的认识。再次总结此篇文章赘述下。

此篇文章，将以创建订单为例，创建不同类型的订单，不同类型的订单不同的处理逻辑。

类图：

代码：

抽象策略（Strategy）角色：抽象策略角色由抽象类或接口来承担，它给出具体策略角色需要实现的接口；

package strategyTest;import strategyTest.dto.BaseRequestDTO;/*** 类 名 称：CreateStrategy* 类 描 述：策略抽象类* 创建时间：2023/2/20 3:46 下午* 创 建 人：admin*/
public abstract class AbstractOrderStrategy {public abstract Boolean isPracticable(BaseRequestDTO dto);// 业务执行总流程public ResponseResult process(BaseRequestDTO dto) {ResponseResult paramsValidate = validateParams(dto);if (!paramsValidate.isSuccess()) {return paramsValidate;}ResponseResult ruleValidate = validateRules(dto);if (!ruleValidate.isSuccess()) {return ruleValidate;}ResponseResult processResult = doProcess(dto);if(processResult.isSuccess()){postProcessAction(dto);}return processResult;}// 参数校验protected abstract ResponseResult validateParams(BaseRequestDTO dto);// 业务规则校验protected abstract ResponseResult validateRules(BaseRequestDTO dto);// 核心实现protected abstract ResponseResult doProcess(BaseRequestDTO dto);// 后置处理(异步操作等)protected abstract void postProcessAction(BaseRequestDTO dto);
}

2.具体策略（ConcreteStrategy）角色：实现封装了具体的算法或行为；

顺风车类型处理：

package strategyTest.impl;import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Service;
import strategyTest.AbstractOrderStrategy;
import strategyTest.ResponseResult;
import strategyTest.dto.BaseRequestDTO;
import strategyTest.dto.SfcRequestDTO;/*** 类 名 称：SfcImpl* 类 描 述：TODO* 创建时间：2023/2/20 3:58 下午* 创 建 人：admin*/
@Service
public class SfcImpl extends AbstractOrderStrategy {private Logger logger = LoggerFactory.getLogger(SfcImpl.class);@Overridepublic Boolean isPracticable(BaseRequestDTO dto) {if(dto.getType() == 1){return true;}return false;}@Overrideprotected ResponseResult validateParams(BaseRequestDTO dto) {SfcRequestDTO sfcRequestDTO = (SfcRequestDTO) dto;if (sfcRequestDTO.getIsShare() == null || sfcRequestDTO.getIsShare() == 0) return ResponseResult.ERROR;logger.info("sfc validateParams success");return ResponseResult.SUCCESS;}@Overrideprotected ResponseResult validateRules(BaseRequestDTO dto) {// 无校验return ResponseResult.SUCCESS;}@Overrideprotected ResponseResult doProcess(BaseRequestDTO dto) {logger.info("sfc doProcess success");return ResponseResult.SUCCESS;}@Overrideprotected void postProcessAction(BaseRequestDTO dto) {logger.info("sfc 异步执行...");}}

巴士订单处理：

package strategyTest.impl;import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Service;
import strategyTest.AbstractOrderStrategy;
import strategyTest.ResponseResult;
import strategyTest.dto.BaseRequestDTO;
import strategyTest.dto.BusRequestDTO;/*** 类 名 称：BusImpl* 类 描 述：TODO* 创建时间：2023/2/20 3:58 下午* 创 建 人：admin*/
@Service
public class BusImpl extends AbstractOrderStrategy {private Logger logger = LoggerFactory.getLogger(BusImpl.class);@Overridepublic Boolean isPracticable(BaseRequestDTO dto) {if (dto.getType() == 2) {return true;}return false;}@Overrideprotected ResponseResult validateParams(BaseRequestDTO dto) {BusRequestDTO busRequestDTO = (BusRequestDTO) dto;if (busRequestDTO.getRouteId() == null || busRequestDTO.getRouteId() == 0) return ResponseResult.ERROR;logger.info("bus validateParams success");return ResponseResult.SUCCESS;}@Overrideprotected ResponseResult validateRules(BaseRequestDTO dto) {BusRequestDTO busRequestDTO = (BusRequestDTO) dto;if (busRequestDTO.getSeats() != null && busRequestDTO.getSeats() > 30) return ResponseResult.ERROR;logger.info("bus validateRules success");return ResponseResult.SUCCESS;}@Overrideprotected ResponseResult doProcess(BaseRequestDTO dto) {logger.info("bus doProcess success");return ResponseResult.SUCCESS;}@Overrideprotected void postProcessAction(BaseRequestDTO dto) {logger.info("bus 异步执行...");}}

3.上下文（Context）角色：持有抽象策略类的引用。（引用，执行策略）

package strategyTest;import org.springframework.beans.factory.BeanFactoryUtils;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.stereotype.Component;
import strategyTest.dto.BaseRequestDTO;import java.util.ArrayList;
import java.util.List;
import java.util.Map;/*** 类 名 称：StrategyContext* 类 描 述：策略执行上下文* 创建时间：2023/2/20 3:47 下午* 创 建 人：admin*/
@Component
public class StrategyContext{// 策略管理类@Autowiredprivate List<AbstractOrderStrategy> strategies = new ArrayList<>();// 获取策略类public AbstractOrderStrategy getStrategy(BaseRequestDTO dto) {for (AbstractOrderStrategy strategy : strategies) {if (strategy.isPracticable(dto)) {return strategy;}}return null;}}

调用方client：

可以在一个controller，也可以写在多个controller

package strategyTest.controller;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import strategyTest.AbstractOrderStrategy;
import strategyTest.ResponseResult;
import strategyTest.StrategyContext;
import strategyTest.dto.BaseRequestDTO;
import strategyTest.dto.BusRequestDTO;
import strategyTest.dto.SfcRequestDTO;/*** 类 名 称：客户端请：可以充当controller或者业务调用上游* 类 描 述：TODO* 创建时间：2023/2/20 3:58 下午* 创 建 人：admin*/
@RestController
public class ClientTest {@Autowiredprivate StrategyContext strategyContext;@RequestMapping("/createSfc")public ResponseResult createSfc(SfcRequestDTO sfcRequestDTO){if(sfcRequestDTO == null){return ResponseResult.ERROR;}return this.createOrder(sfcRequestDTO);}@RequestMapping("/createBus")public ResponseResult createBus(BusRequestDTO busRequestDTO){if(busRequestDTO == null){return ResponseResult.ERROR;}return this.createOrder(busRequestDTO);}private ResponseResult createOrder(BaseRequestDTO baseRequestDTO) {AbstractOrderStrategy strategy = strategyContext.getStrategy(baseRequestDTO);if(strategy == null){return ResponseResult.ERROR;}return strategy.process(baseRequestDTO);}
}