基于策略模式动态选择不同地区霸王餐API接口的路由实现

在"吃喝不愁"App的全国化运营中，不同城市或区域（如北京、上海、成都）对接的"霸王餐"营销活动由本地服务商独立提供，其API地址、认证方式、请求参数格式均存在差异。若采用硬编码分支判断，将导致代码臃肿且难以维护。本文通过策略模式（Strategy Pattern） 结合Spring容器管理，实现灵活、可扩展的地区级API路由机制，并提供完整的Java工程示例。

定义统一接口与策略上下文

首先，抽象出所有地区API的共性行为------提交用户参与请求并返回结果：

java 复制代码

package juwatech.cn.strategy;

public interface FreeMealApiStrategy {
    String getRegionCode();
    FreeMealResponse claim(FreeMealRequest request);
}

其中，FreeMealRequest 和 FreeMealResponse 为通用DTO：

java 复制代码

package juwatech.cn.dto;

public class FreeMealRequest {
    private Long userId;
    private String activityId;
    private String cityCode;
    // getters/setters omitted
}

public class FreeMealResponse {
    private boolean success;
    private String message;
    private String couponCode;
    // getters/setters omitted
}

策略上下文负责根据地区码动态选择具体实现：

java 复制代码

package juwatech.cn.strategy;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import javax.annotation.PostConstruct;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

@Component
public class FreeMealApiRouter {

    private final Map<String, FreeMealApiStrategy> strategyMap = new ConcurrentHashMap<>();

    @Autowired
    public FreeMealApiRouter(List<FreeMealtApiStrategy> strategies) {
        for (FreeMealApiStrategy strategy : strategies) {
            strategyMap.put(strategy.getRegionCode(), strategy);
        }
    }

    public FreeMealResponse route(FreeMealRequest request) {
        String region = request.getCityCode().substring(0, 2); // 如"10"代表北京
        FreeMealApiStrategy strategy = strategyMap.get(region);
        if (strategy == null) {
            throw new IllegalArgumentException("Unsupported region: " + region);
        }
        return strategy.claim(request);
    }
}

实现各地区具体策略

以北京（BJ）和成都（CD）为例，分别实现策略类：

java 复制代码

package juwatech.cn.strategy.impl;

import juwatech.cn.dto.FreeMealRequest;
import juwatech.cn.dto.FreeMealResponse;
import juwatech.cn.strategy.FreeMealApiStrategy;
import org.springframework.stereotype.Component;

@Component
public class BeijingFreeMealStrategy implements FreeMealApiStrategy {

    @Override
    public String getRegionCode() {
        return "10"; // 北京区号前缀
    }

    @Override
    public FreeMealResponse claim(FreeMealRequest request) {
        // 调用北京专属API：https://bj-promo.eat.com/api/v1/free-meal
        // 此处可集成Feign或RestTemplate
        FreeMealResponse response = new FreeMealResponse();
        response.setSuccess(true);
        response.setMessage("Beijing free meal claimed");
        response.setCouponCode("BJ2025" + request.getUserId());
        return response;
    }
}

java 复制代码

package juwatech.cn.strategy.impl;

import juwatech.cn.dto.FreeMealRequest;
import juwatech.cn.dto.FreeMealResponse;
import juwatech.cn.strategy.FreeMealApiStrategy;
import org.springframework.stereotype.Component;

@Component
public class ChengduFreeMealStrategy implements FreeMealApiStrategy {

    @Override
    public String getRegionCode() {
        return "28"; // 成都区号前缀
    }

    @Override
    public FreeMealResponse claim(FreeMealRequest request) {
        // 调用成都专属API：https://cd-deals.eat.com/open/free
        FreeMealResponse response = new FreeMealResponse();
        response.setSuccess(true);
        response.setMessage("Chengdu free meal issued");
        response.setCouponCode("CD2025" + request.getUserId());
        return response;
    }
}

每个策略类通过@Component自动注册到Spring容器，FreeMealApiRouter在初始化时通过构造注入收集所有实现。

业务服务调用路由

在订单或营销服务中直接使用路由器：

java 复制代码

package juwatech.cn.service;

import juwatech.cn.dto.FreeMealRequest;
import juwatech.cn.dto.FreeMealResponse;
import juwatech.cn.strategy.FreeMealApiRouter;
import org.springframework.stereotype.Service;

@Service
public class FreeMealClaimService {

    private final FreeMealApiRouter router;

    public FreeMealClaimService(FreeMealApiRouter router) {
        this.router = router;
    }

    public FreeMealResponse handleClaim(Long userId, String activityId, String cityCode) {
        FreeMealRequest request = new FreeMealRequest();
        request.setUserId(userId);
        request.setActivityId(activityId);
        request.setCityCode(cityCode);

        return router.route(request);
    }
}

支持动态扩展与配置化

若未来新增城市（如深圳），只需新增一个ShenzhenFreeMealStrategy实现类并标注@Component，无需修改路由逻辑。若需从配置中心加载地区映射，可将regionCode改为读取@Value或Nacos配置，进一步解耦。

此外，可结合工厂模式或注解驱动（如自定义@Region("30")）增强灵活性，但策略模式已满足当前核心需求：开闭原则 （对扩展开放，对修改关闭）与单一职责（每个地区逻辑独立）。

本文著作权归吃喝不愁app开发者团队，转载请注明出处！