如何使用python在twitter上使用hashtags？(How to use the hashtags on twitter using python?)

 只有在Spring Context中只存在一个特定类型的实现bean时，自动装配才有效。 我假设使用泛型D扩展BaseDao导致Spring试图自动装配BaseDao实例而不是UserDao和ApprovalDao的情况。 因为UserDao和ApprovalDao都实现了BaseDao，所以Spring上下文包含BaseDao的多个实现，无法决定应该使用哪个。 
 
 Spring试图在堆栈跟踪中告诉你 
 
org.springframework.beans.factory.NoSuchBeanDefinitionException: 
__No unique bean of type__ [com.primetech.core.parent.BaseDAO] is defined:
expected single matching bean but found 2: [userDAO, approvalDAO]
 
 您可以尝试使用实际dao类型在具体服务中定义dao来测试这一点，例如 
 
public abstract class BaseService<K, E extends BaseEntity, D extends BaseDAO<K, E>> {
   private final D dao;
   protected BaseService(D dao) {
      this.dao = dao;
   } 
}

public class UserService extends BaseService<K, User, UserDao<K, User>> {
   @Autowired
   public UserService(UserDao dao) {
     super(dao);
   }
}
 
 我将继续为UserDao和ApprovalDao定义接口，以便依赖关系在接口而不是实现上。 daos可能仍然具有共同的超级接口，并且它们的实现可以基于BaseDao以避免不必要的重复。 
 
 在示例中，我在构造函数中定义了注入的Dao，因为我假设在服务的整个生命周期中应该使用相同的dao实例，并且如果没有dao set，服务就不能存在。 在我看来，构造函数参数更好地传达了这个契约。 此外，它可能使该类更易于测试和维护。 

Autowiring works only if there is exactly one implementation bean of the specific type present in the Spring Context. I'd assume that using the generic D extends BaseDao leads to a situation where Spring is trying to autowire instances of BaseDao instead of UserDao and ApprovalDao. Because you both UserDao and ApprovalDao implement BaseDao, Spring context contains multiple implementations of BaseDao and cannot decide which one should be used. 
 
Spring is trying to tell this to you in the stack trace 
 
org.springframework.beans.factory.NoSuchBeanDefinitionException: 
__No unique bean of type__ [com.primetech.core.parent.BaseDAO] is defined:
expected single matching bean but found 2: [userDAO, approvalDAO]
 
You could try to test this by defining the dao in the concrete service using the actual dao type e.g.
 
public abstract class BaseService<K, E extends BaseEntity, D extends BaseDAO<K, E>> {
   private final D dao;
   protected BaseService(D dao) {
      this.dao = dao;
   } 
}

public class UserService extends BaseService<K, User, UserDao<K, User>> {
   @Autowired
   public UserService(UserDao dao) {
     super(dao);
   }
}
 
I'd continue by defining interfaces for UserDao and ApprovalDao so that dependencies are on interfaces and not implementations. The daos may still have a common super interface and their implementations may be based on the BaseDao to avoid unnecessary duplication.
 
In the example I've defined the injected Dao in the constructor because I assume that the same dao instance should be used throughout the lifetime of the service and the service cannot exist without the dao set. In my opinion, a constructor argument communicates this contract better. Furthermore it might make the class a bit more testable and maintainable.