Java设计模式之策略模式的实际应用案例

// 策略接口
public interface DiscountStrategy {
    BigDecimal applyDiscount(Order order);
}

// 具体策略1：新人折扣
public class NewUserDiscountStrategy implements DiscountStrategy {
    @Override
    public BigDecimal applyDiscount(Order order) {
        // 假设只有新用户才享受此折扣
        if (order.isNewUser()) {
            return order.getTotalAmount().multiply(new BigDecimal("0.9")); // 9折
        }
        return order.getTotalAmount();
    }
}

// 具体策略2：满减折扣
public class FullReductionStrategy implements DiscountStrategy {
    private BigDecimal threshold;
    private BigDecimal reductionAmount;

    public FullReductionStrategy(BigDecimal threshold, BigDecimal reductionAmount) {
        this.threshold = threshold;
        this.reductionAmount = reductionAmount;
    }

    @Override
    public BigDecimal applyDiscount(Order order) {
        if (order.getTotalAmount().compareTo(threshold) >= 0) {
            return order.getTotalAmount().subtract(reductionAmount);
        }
        return order.getTotalAmount();
    }
}

// 上下文：订单服务
public class OrderService {
    private List<DiscountStrategy> strategies;

    public OrderService(List<DiscountStrategy> strategies) {
        this.strategies = strategies;
    }

    public BigDecimal calculateFinalPrice(Order order) {
        BigDecimal finalPrice = order.getTotalAmount();
        for (DiscountStrategy strategy : strategies) {
            // 这里可以设计成链式调用，或者叠加折扣
            finalPrice = strategy.applyDiscount(order); // 简化处理，假设是顺序应用
        }
        return finalPrice;
    }
}

public void processData(String dataType, String data) {
    if ("XML".equals(dataType)) {
        // 解析XML逻辑
    } else if ("JSON".equals(dataType)) {
        // 解析JSON逻辑
    } else if ("CSV".equals(dataType)) {
        // 解析CSV逻辑
    } else {
        throw new IllegalArgumentException("Unsupported data type");
    }
}

// 策略接口
public interface DataParser {
    void parse(String data);
}

// 具体策略：XML解析器
public class XmlDataParser implements DataParser {
    @Override
    public void parse(String data) {
        System.out.println("Parsing XML data...");
        // 实际XML解析逻辑
    }
}

// 具体策略：JSON解析器
public class JsonDataParser implements DataParser {
    @Override
    public void parse(String data) {
        System.out.println("Parsing JSON data...");
        // 实际JSON解析逻辑
    }
}

// 上下文：数据处理服务
public class DataProcessingService {
    private Map<String, DataParser> parserMap;

    public DataProcessingService() {
        parserMap = new HashMap<>();
        parserMap.put("XML", new XmlDataParser());
        parserMap.put("JSON", new JsonDataParser());
        // 可以通过工厂模式或Spring IoC来管理这些策略实例
    }

    public void process(String dataType, String data) {
        DataParser parser = parserMap.get(dataType);
        if (parser == null) {
            throw new IllegalArgumentException("Unsupported data type: " + dataType);
        }
        parser.parse(data);
    }
}