JAVA配置類

@Configuration //通過該注解來表明該類是一個Spring的配置，相當(dāng)于一個xml文件
@ComponentScan(basePackages = "com.marx.config") //配置掃描包
public class SpringConfig {

    @Bean // 通過該注解來表明是一個Bean對象，相當(dāng)于xml中的<bean>
    public UserDAO getUserDAO(){
        return new UserDAO(); // 直接new對象做演示
    }

}

Service層

@Service
public class UserService {

    @Autowired // 注入Spring容器中的bean對象
    private UserDAO userDAO;

    public List<User> queryUserList() {
        // 調(diào)用userDAO中的方法進(jìn)行查詢
        return this.userDAO.queryUserList();
    }

}

DAO層

public class UserDAO {
    public List<User> queryUserList(){
        List<User> result = new ArrayList<User>();
        // 模擬數(shù)據(jù)庫的查詢
        for (int i = 0; i < 10; i++) {
            User user = new User();
            user.setUsername("username_" + i);
            user.setPassword("password_" + i);
            user.setAge(i + 1);
            result.add(user);
        }
        return result;
    }

}

測試類

public class Test1 {
    public static void main(String[] args) {
        // 通過Java配置來實例化Spring容器
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(SpringConfig.class);

        // 在Spring容器中獲取Bean對象
        UserService userService = context.getBean(UserService.class);

        // 調(diào)用對象中的方法
        List<User> list = userService.queryUserList();
        for (User user : list) {
            System.out.println(user.getUsername() + ", " + user.getPassword() + ", " + user.getPassword());
        }

        // 銷毀該容器
        context.destroy();
    }

}

報錯
Exception in thread "main" org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.marx.service.UserService' available

at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:353)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:340)
at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1093)
at com.marx.test.Test1.main(Test1.java:16)