Spring Boot自动扫描

桃扇骨 2024-04-18 07:55 83阅读 0赞

转自： [https://www.cnblogs.com/javJoker/p/7352818.html][https_www.cnblogs.com_javJoker_p_7352818.html]

进行Spring Boot和Mybatis进行整合的时候，Spring Boot注解扫描的时候无法扫描到Application类的以外的包下面的注解，如下图：

![format_png][]

App就是Application类，下图是ProductMapper 类：

![复制代码][aHR0cHM6Ly9jb21tb24uY25ibG9ncy5jb20vaW1hZ2VzL2NvcHljb2RlLmdpZg]

@Mapper
 public interface ProductMapper {
 
 @Insert("insert into products (pname,type,price)values(#{pname},#{type},#{price}")
 public int add(Product product);
 
 @Delete("delete from products where id=#{arg1}")
 public int deleteById(int id);
 
 @Update("update products set pname=#{pname},type=#{type},price=#{price} where id=#{id}")
 public int update(Product product);
 
 @Select("select * from products where id=#[arg1}")
 public Product getById(int id);
 
 @Select("select * from productsorder by id desc")
 public List<Product> queryByLists();
 }

![复制代码][aHR0cHM6Ly9jb21tb24uY25ibG9ncy5jb20vaW1hZ2VzL2NvcHljb2RlLmdpZg]

App类运行的时候后台就会报没有找到ProductMapper 这个类bean:

<table> 
 <tbody> 
 <tr> 
 <td> 1 2 3 4 5 </td> 
 <td> <code>Exception in thread "main" org.springframework.beans.factory.NoSuchBeanDefinitionException:&lt;</code><code>br</code><code>&gt; No qualifying bean of type 'com.self.spring.mapper.ProductMapper' available</code> <code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:353)</code> <code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:340)</code> <code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1090)</code> <code>&nbsp;&nbsp;&nbsp;&nbsp;</code><code>at com.self.spring.springboot.App.main(App.java:17)</code> </td> 
 </tr> 
 </tbody> 
</table>

造成上面的错误原因：SpringBoot项目的Bean装配默认规则是根据Application类所在的包位置从上往下扫描！ “Application类”是指SpringBoot项目入口类。这个类的位置很关键：

如果Application类所在的包为：`io.github.gefangshuai.app`，则只会扫描`io.github.gefangshuai.app`包及其所有子包，如果service或dao所在包不在`io.github.gefangshuai.app`及其子包下，则不会被扫描！

**解决方法**

第一种：Application类放在父包下面，所有有注解的类放在同一个下面或者其子包下面

第二种：指定要进行扫描注解的包URL，上面的问题的解决方案可以在Application类上面加注解扫描mapper接口包下面的类。

![复制代码][aHR0cHM6Ly9jb21tb24uY25ibG9ncy5jb20vaW1hZ2VzL2NvcHljb2RlLmdpZg]

@SpringBootApplication
    @MapperScan(basePackages="com.self.spring.springboot.mapper")
    public class App {
        public static void main(String[] args) {
            ConfigurableApplicationContext context = SpringApplication.run(App.class, args);
            System.out.println(context.getBean(ProductMapper.class));
            context.close();
        }
    }

![复制代码][aHR0cHM6Ly9jb21tb24uY25ibG9ncy5jb20vaW1hZ2VzL2NvcHljb2RlLmdpZg]

[https_www.cnblogs.com_javJoker_p_7352818.html]: https://www.cnblogs.com/javJoker/p/7352818.html
[format_png]: https://imgconvert.csdnimg.cn/aHR0cHM6Ly9pbWFnZXMyMDE3LmNuYmxvZ3MuY29tL2Jsb2cvNjI3NTQ4LzIwMTcwOC82Mjc1NDgtMjAxNzA4MTMxMTE2NTA5MTMtMTQzODkzMDcyNy5wbmc?x-oss-process=image/format,png
[aHR0cHM6Ly9jb21tb24uY25ibG9ncy5jb20vaW1hZ2VzL2NvcHljb2RlLmdpZg]: https://imgconvert.csdnimg.cn/aHR0cHM6Ly9jb21tb24uY25ibG9ncy5jb20vaW1hZ2VzL2NvcHljb2RlLmdpZg