《读spring源码》12实现ImportSelector接口引入多个类全名然后引入容器多个bean

我不是女神ヾ 2023-06-18 06:53 6阅读 0赞

![在这里插入图片描述][20191130202106225.png]  
我们可以通过实现ImportSelector接口引入多个 类全名然后 引入容器多个bean 示例如下：

package test;
    
    import com.enjoy.cap6.MainConfig;
    import org.junit.jupiter.api.Test;
    import org.springframework.context.annotation.AnnotationConfigApplicationContext;
    
    /** * FactoryBean 和 BeanFactorty 有什么区别？ * * FactoryBean ：可以把我们的JAVA实例通过FactoryBean注入到容器中 * * BeanFactorty：从我们的容器中获取实例化后的bean * */
    public class MainTEwst6 { 
    
    
        @Test
        public void sss(){ 
            AnnotationConfigApplicationContext annotationConfigApplicationContext = new AnnotationConfigApplicationContext(MainConfig.class);
            String[] beanDefinitionNames = annotationConfigApplicationContext.getBeanDefinitionNames();
            for(String name :beanDefinitionNames){ 
                System.out.println(name);
            }
        }
    }

package com.enjoy.cap6;
    
    
    import com.enjoy.cap1.Person;
    import com.enjoy.cap5.LinCodition;
    import com.enjoy.cap5.WinCodition;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Conditional;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.context.annotation.Import;
    
    @Configuration
    @Import(value = { Dog.class,Cat.class,TTTTImportSelector.class})
    public class MainConfig { 
    
        /** * 1、@Bean 【导入第三方的类或包的组件】,比如Person为第三方的类，需要我们IOC使用时 * 2、包扫描＋组件的标注注解（@ComponentScan：@Controller，@Service，@Repository，@Componet）一般针对自己写的类 * 3、@Import：【快速给容器导入一个组件】注意@Bean有点简单 * 1)@Import(要导入到容器中的组件)：容器会自动注册这个组件，bean的id为全类名 * 2）ImportSelector：是一个接口，返回需要导入到容器的组件的全类名数组。 * * 容器启动时初始化person的bean实例 * * @return */
        @Bean("person")
        public Person zhangsan(){ 
            System.out.println("给我们的容器中添加张三");
            return new Person("张三",22);
        }
    
    
    }

package com.enjoy.cap6;
    
    
    import org.springframework.context.annotation.ImportSelector;
    import org.springframework.core.type.AnnotationMetadata;
    
    public class TTTTImportSelector implements ImportSelector { 
    
    
        @Override
        public String[] selectImports(AnnotationMetadata importingClassMetadata) { 
    
            return new String[]{ "com.enjoy.cap6.Fish","com.enjoy.cap6.Tiger"};
        }
    }

测试结果：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Bwd3dw_size_16_color_FFFFFF_t_70]

如果返回null的话会报错：

package com.enjoy.cap6;
    
    
    import org.springframework.context.annotation.ImportSelector;
    import org.springframework.core.type.AnnotationMetadata;
    
    public class TTTTImportSelector implements ImportSelector { 
    
        /** * * @param importingClassMetadata * @return */
        @Override
        public String[] selectImports(AnnotationMetadata importingClassMetadata) { 
    
            return null;
        }
    }

报错如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Bwd3dw_size_16_color_FFFFFF_t_70 1]  
我们debug进去看看  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Bwd3dw_size_16_color_FFFFFF_t_70 2]  
进入了 config解析器

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Bwd3dw_size_16_color_FFFFFF_t_70 3]

[20191130202106225.png]: https://img-blog.csdnimg.cn/20191130202106225.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Bwd3dw_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20191130202422969.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Bwd3dw,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Bwd3dw_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20191130201620927.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Bwd3dw,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Bwd3dw_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/20191130201736517.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Bwd3dw,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Bwd3dw_size_16_color_FFFFFF_t_70 3]: https://img-blog.csdnimg.cn/20191130201848399.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Bwd3dw,size_16,color_FFFFFF,t_70