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策略模式 vs 适配器模式

news 2025/8/22 6:41:14

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

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

`2.2支付宝适配器`

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 final AlipayService 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); }
}