适配器工厂

• 使用背景

  根据不同的类型，会有不同的业务逻辑

• 举例

  判断一个字段shop：TB/TM/JD/FXG/KS/…..

  会调用不同商家api进行不同的处理逻辑

• 技术点

  org.springframework.core.annotation.AnnotationUtils+SpringIOC+注解

• 使用举例

  • 适配器工厂

  public class AdapterFactory {
  	//一个会多线程访问的缓存Map
    private static final ConcurrentMap<String, Object> INSTANCE_MAP = new ConcurrentHashMap<>();
  	//获取IOC容器中对应标记@Adapter注解的Bean
    public static <T> T getInstance(Class<T> type, String source) {
      Map<String, T> maps = ApplicationContextUtil.getApplicationContext().getBeansOfType(type);
      if (maps.isEmpty()) {
        throw new AdapterException("找不到对应的实例type=" + type.getName() + ";source=" + source);
      }
      String key = source + "_" + type.getName();
  
      Object t = INSTANCE_MAP.get(key);
      if (t != null) {
        return type.cast(t);
      }
      for (T obj : maps.values()) {
        Adapter adapter = AnnotationUtils.findAnnotation(obj.getClass(), Adapter.class);
        if (adapter != null && contains(adapter.value(), source)) {
          T instance = type.cast(obj);
          INSTANCE_MAP.putIfAbsent(key, instance);
          return instance;
        }
      }
      throw new AdapterException("找不到对应的实例type=" + type.getName() + ";source=" + source);
    }
  
    private static boolean contains(String[] sourceArr, String source) {
      if (sourceArr == null || StringUtils.isEmpty(source)) {
        return false;
      }
      for (String s : sourceArr) {
        if (source.equals(s)) {
          return true;
        }
      }
      return false;
    }
  
  }

  • @Adapter注解

  import org.springframework.core.annotation.AliasFor;
  import java.lang.annotation.*;
  
  @Target({ElementType.TYPE})
  @Retention(RetentionPolicy.RUNTIME)
  @Documented
  public @interface Adapter {
      @AliasFor(attribute = "platform")
      String[] value() default {};
  
      @AliasFor(attribute = "value")
      String[] platform() default {};
  }

• 使用举例

public interface CatTemplete {
  void miao();
}

@Adapter("blackCat")
@Component
public class BlackCatTempleteImpl implements CatTemplete{
  void miao(){
    System.out.println("im black cat");
  }
}

@Adapter("whiteCat")
@Component
public class whiteCatTempleteImpl implements CatTemplete{
  void miao(){
    System.out.println("im white cat");
  }
}

public void test(){
  CatTemplete catTemplete = AdapterFactory.getInstance(CatTemplete.class, "blackCat");
  catTemplete.miao();
}