# 工厂模式知识库

pattern:
  id: "factory-pattern"
  name: "工厂模式"
  category: "创建型模式"
  description: "定义一个创建对象的接口，让子类决定实例化哪一个类，使一个类的实例化延迟到其子类"

# 模式结构
structure:
  participants:
    - name: "Factory"
      role: "抽象工厂接口"
      description: "声明创建产品对象的抽象方法"
    - name: "ConcreteFactory"
      role: "具体工厂"
      description: "实现抽象工厂接口，创建具体产品"
    - name: "Product"
      role: "抽象产品"
      description: "定义产品的共同接口"
    - name: "ConcreteProduct"
      role: "具体产品"
      description: "实现抽象产品接口的具体类"

# 项目中的应用
applications:
  - module: "pay"
    location: "PayClientFactory"
    purpose: "创建支付客户端实例"
    code_path: "yudao-module-pay/.../pay/core/client/PayClientFactory.java"
    implementation: |
      public interface PayClientFactory {
          PayClient getPayClient(Long channelId);
          <Config extends PayClientConfig> PayClient createOrUpdatePayClient(
              Long channelId, String channelCode, Config config);
      }

  - module: "infra/sms"
    location: "SmsClientFactory"
    purpose: "创建短信客户端实例"
    code_path: "yudao-module-infra/.../sms/core/client/SmsClientFactory.java"
    implementation: |
      public class SmsClientFactoryImpl implements SmsClientFactory {
          private final ConcurrentMap<Long, AbstractSmsClient> channelIdClients = new ConcurrentHashMap<>();

          @Override
          public SmsClient createOrUpdateSmsClient(SmsChannelProperties properties) {
              AbstractSmsClient client = channelIdClients.get(properties.getId());
              if (client == null) {
                  client = this.createSmsClient(properties);
                  client.init();
                  channelIdClients.put(client.getId(), client);
              } else {
                  client.refresh(properties);
              }
              return client;
          }
      }

# 使用场景
scenarios:
  - "需要根据配置动态创建不同类型的客户端"
  - "需要管理多个同类对象的实例（如缓存）"
  - "创建逻辑复杂，需要封装"
  - "需要支持扩展新的产品类型"

# 优点
advantages:
  - "解耦创建逻辑和使用逻辑"
  - "便于扩展新产品类型"
  - "可以缓存和复用对象实例"
  - "统一管理对象生命周期"

# 缺点
disadvantages:
  - "增加了类的数量"
  - "需要维护工厂类的实现"

# 扩展指南
extension_guide:
  title: "如何新增产品类型"
  steps:
    - step: 1
      action: "创建具体产品类"
      description: "实现Product接口"
    - step: 2
      action: "修改工厂创建逻辑"
      description: "在工厂中添加新类型的创建分支"
    - step: 3
      action: "配置支持"
      description: "添加配置枚举或配置项"