Java 无法自动关联字段，但我有定义

我的app-config.xml为我的userdaobean提供了一个定义：

  <bean id="userDao" class="com.blah.core.db.hibernate.UserDaoImpl">
        <property name="sessionFactory" ref="sessionFactory"/>
    </bean>

“getTestUser（）”是一个引用UserDao的新方法，它看起来像：

@Service
public class UserServiceImpl implements UserService{

    @Autowired
    UserDao userDao;

    public String sayHello() {

        return "hello from user service impl part 2";

    }

    public String getTestUser() {


        return userDao.getById(1L).getUsername();

    }


}

我得到一个错误：

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userServiceImpl': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: com.blah.core.db.hibernate.UserDao com.blah.core.services.UserServiceImpl.userDao; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No matching bean of type [com.blah.core.db.hibernate.UserDao] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}

问题可能是什么

如果我没有做autowire，我会做什么来代替在UserDao定义中添加@autowire呢

---

您是否尝试过导出Spring的所有注册bean（或通过读取或内存），以确定

userDao

bean是否在列表中。请确保

UserDaoImpl

也真正实现了

UserDao

——我指的是这一点，因为我在这里没有看到

UserDaoImpl

的片段

---

如果您不使用

@Autowired

，另一种方法是通过ApplicationContext（这被认为是一种肮脏的方式，请改为修复您的

@Autowired

）通过bean名称、类名等显式获取bean的引用。

好的，我没有实现UserDao啊！谢谢顺便说一句，你如何通过调试读取spring的引导日志或内存？）这些都是我应该学习的好技能！我已更新了有关日志记录和调试的答案。：）

@Service
public class UserServiceImpl implements UserService{

    @Autowired
    UserDao userDao;

    public String sayHello() {

        return "hello from user service impl part 2";

    }

    public String getTestUser() {


        return userDao.getById(1L).getUsername();

    }


}

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userServiceImpl': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: com.blah.core.db.hibernate.UserDao com.blah.core.services.UserServiceImpl.userDao; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No matching bean of type [com.blah.core.db.hibernate.UserDao] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}