策略模式 vs 适配器模式

原创已于 2025-08-25 09:29:44 修改 · 594 阅读

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文章标签：

#spring boot #java #策略模式 #适配器模式

于 2025-08-21 09:46:51 首次发布

一、模式本质

1 策略模式：行为的选择

核心思想：定义一组算法，将每个算法封装起来，并使它们可以互相替换，让算法的变化独立于使用它的客户端。

2 适配器模式：接口的转换

核心思想：将一个类的接口转换成客户端期望的另一个接口，使原本因接口不兼容而无法协同工作的类能够协同工作。

二、策略模式应用

1、策略模式模拟商品折扣算法

Vip折扣、促销折扣、满减折扣

2、策略实现

`2.1定义策略接口`

public interface DiscountStrategy {    

    BigDecimal calculateDiscount(Order order);

}

2.2vip折扣

@Service("vipDiscount")
public class VipDiscountStrategy implements DiscountStrategy {
    
    @Override
    public BigDecimal calculateDiscount(Order order) {
        return order.getAmount().multiply(BigDecimal.valueOf(0.9));

    }
}

`2.3促销折扣`

@Service("promotionDiscount")
public class PromotionDiscountStrategy implements DiscountStrategy {
    
    @Override
    public BigDecimal calculateDiscount(Order order) {
        return order.getAmount().multiply(BigDecimal.valueOf(0.8));
    }
}

2.4满减折扣

@Service("fullReductionDiscount")
public class FullReductionDiscountStrategy implements DiscountStrategy {
    
    @Override
    public BigDecimal calculateDiscount(Order order) {
        if (order.getAmount().compareTo(BigDecimal.valueOf(100)) > 0) {
            return order.getAmount().subtract(BigDecimal.valueOf(20));
        }
        return order.getAmount();
    }
}

2.5策略核心

@Service
public class DiscountContext {

    private final Map<String, DiscountStrategy> strategyMap;

    @Autowired
    public DiscountContext(Map<String, DiscountStrategy> strategyMap) {
        this.strategyMap = strategyMap;
    }

    public BigDecimal applyDiscount(String strategyName, Order order) {
        DiscountStrategy strategy = strategyMap.get(strategyName);
        if (strategy == null) {
            throw new IllegalArgumentException("未知折扣策略: " + strategyName);
        }
        return strategy.calculateDiscount(order);
    }
}

2.6控制器调用

@RestController

@RequestMapping("/orders")

public class OrderController {    

   @Autowired
   private DiscountContext discountContext;

    @PostMapping("/calculate")       public BigDecimal calculatePrice(@RequestParam String discountType,                                     @RequestBody Order order) {                
      return discountContext.applyDiscount(discountType + "Discount", order);    
   }
}

3、策略模式优势

新增折扣策略只需添加新类

避免多层if-else判断

策略算法可独立测试

三、适配器模式应用

1、适配器模式模拟统一支付接口

需要接入支付宝、微信支付和PayPal，但三家接口完全不同

2、适配器实现

2.1定义统一支付接口

`2.2支付宝适配器`

public interface PaymentGateway {
    PaymentResult pay(BigDecimal amount, String orderId);
}

2.2.1原生接口

public class AlipayService {

    public AlipayResponse createPayment(AlipayRequest request) {
        // 支付宝原生逻辑
    }
}

2.2.2支付宝适配器

@Service
public class AlipayAdapter implements PaymentGateway {
    private finalAlipayService alipayService;

    @Override
    public PaymentResult pay(BigDecimal amount, String orderId) {            // 转换参数        

        AlipayRequest request = new AlipayRequest(amount, orderId);
        // 调用原生接口        

        AlipayResponse response = alipayService.createPayment(request);
        // 转换结果        

        return new PaymentResult(

                response.isSuccess(), response.getTransactionId()

        );
    }
}

`2.3微信支付适配器`

@Service
public class WechatPayAdapter implements PaymentGateway {
    private final WechatPayService wechatService;

    @Override
    public PaymentResult pay(BigDecimal amount, String orderId) {           
        // 转换并调用微信接口   

    }
}

`2.4Paypal支付适配器`

@Service
public class PayPalAdapter implements PaymentGateway {
    private final PayPalClient paypalClient;

    @Override
    public PaymentResult pay(BigDecimal amount, String orderId) {           // 转换并调用PayPal接口

    }

}

`2.5统一支付实现`

@Service
public class PaymentService {
    private final Map<String, PaymentGateway> gateways;

    @Autowired

    public PaymentService(List<PaymentGateway> gatewayList) {
        this.gateways = gatewayList.stream().collect(Collectors.toMap(g -> g.getClass().getSimpleName().replace("Adapter", "").toLowerCase(), Function.identity()));
    }

    public PaymentResult processPayment(String gatewayType, BigDecimal amount, String orderId) {
        PaymentGateway gateway = gateways.get(gatewayType);
        if (gateway == null) {
            throw new IllegalArgumentException("不支持的支付方式: " + gatewayType);
        }
        return gateway.pay(amount, orderId);
    }

}