- componentScan掃描@Repository,@Service、@Controller，@Component註解的類
- @Configuration配置類
- xml檔案定義
- 使用工廠bean：FactoryBean
- 使用@Import註解，
通常跟@Configuration一起使用，常常使用在bean依賴場景中，比如springboot的自動配置類經常使用到，會將@Import註解中類註冊到spring容器中，涉及的類會遞迴註冊
- BeanDefinitionRegistryPostProcessor
spring提供的鉤子函式之一，實現該介面的類會在spring容器例項化bean之前執行
- @Import + @ImportSelector
public interface ImportSelector {
/**
* Select and return the names of which class(es) should be imported based on
* the {@link AnnotationMetadata} of the importing @{@link Configuration} class.
* @return the class names, or an empty array if none
*/
String[] selectImports(AnnotationMetadata importingClassMetadata);
/**
* Return a predicate for excluding classes from the import candidates, to be
* transitively applied to all classes found through this selector's imports.
* <p>If this predicate returns {@code true} for a given fully-qualified
* class name, said class will not be considered as an imported configuration
* class, bypassing class file loading as well as metadata introspection.
* @return the filter predicate for fully-qualified candidate class names
* of transitively imported configuration classes, or {@code null} if none
* @since 5.2.4
*/
@Nullable
default Predicate<String> getExclusionFilter() {
return null;
}
selectImports方法需要返回需要註冊為bean的類名陣列，入參是@Import註解類的後設資料，如果類為@Configuration，涉及的類會遞迴註冊
- @Import + @ImportBeanDefinitionRegistrar
/**
* Interface to be implemented by types that register additional bean definitions when
* processing @{@link Configuration} classes. Useful when operating at the bean definition
* level (as opposed to {@code @Bean} method/instance level) is desired or necessary.
*
* <p>Along with {@code @Configuration} and {@link ImportSelector}, classes of this type
* may be provided to the @{@link Import} annotation (or may also be returned from an
* {@code ImportSelector}).
*
* <p>An {@link ImportBeanDefinitionRegistrar} may implement any of the following
* {@link org.springframework.beans.factory.Aware Aware} interfaces, and their respective
* methods will be called prior to {@link #registerBeanDefinitions}:
* <ul>
* <li>{@link org.springframework.context.EnvironmentAware EnvironmentAware}</li>
* <li>{@link org.springframework.beans.factory.BeanFactoryAware BeanFactoryAware}
* <li>{@link org.springframework.beans.factory.BeanClassLoaderAware BeanClassLoaderAware}
* <li>{@link org.springframework.context.ResourceLoaderAware ResourceLoaderAware}
* </ul>
*
* <p>Alternatively, the class may provide a single constructor with one or more of
* the following supported parameter types:
* <ul>
* <li>{@link org.springframework.core.env.Environment Environment}</li>
* <li>{@link org.springframework.beans.factory.BeanFactory BeanFactory}</li>
* <li>{@link java.lang.ClassLoader ClassLoader}</li>
* <li>{@link org.springframework.core.io.ResourceLoader ResourceLoader}</li>
* </ul>
*
* <p>See implementations and associated unit tests for usage examples.
*
* @author Chris Beams
* @author Juergen Hoeller
* @since 3.1
* @see Import
* @see ImportSelector
* @see Configuration
*/
public interface ImportBeanDefinitionRegistrar {
/**
* Register bean definitions as necessary based on the given annotation metadata of
* the importing {@code @Configuration} class.
* <p>Note that {@link BeanDefinitionRegistryPostProcessor} types may <em>not</em> be
* registered here, due to lifecycle constraints related to {@code @Configuration}
* class processing.
* <p>The default implementation delegates to
* {@link #registerBeanDefinitions(AnnotationMetadata, BeanDefinitionRegistry)}.
* @param importingClassMetadata annotation metadata of the importing class
* @param registry current bean definition registry
* @param importBeanNameGenerator the bean name generator strategy for imported beans:
* {@link ConfigurationClassPostProcessor#IMPORT_BEAN_NAME_GENERATOR} by default, or a
* user-provided one if {@link ConfigurationClassPostProcessor#setBeanNameGenerator}
* has been set. In the latter case, the passed-in strategy will be the same used for
* component scanning in the containing application context (otherwise, the default
* component-scan naming strategy is {@link AnnotationBeanNameGenerator#INSTANCE}).
* @since 5.2
* @see ConfigurationClassPostProcessor#IMPORT_BEAN_NAME_GENERATOR
* @see ConfigurationClassPostProcessor#setBeanNameGenerator
*/
default void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry,
BeanNameGenerator importBeanNameGenerator) {
registerBeanDefinitions(importingClassMetadata, registry);
}
/**
* Register bean definitions as necessary based on the given annotation metadata of
* the importing {@code @Configuration} class.
* <p>Note that {@link BeanDefinitionRegistryPostProcessor} types may <em>not</em> be
* registered here, due to lifecycle constraints related to {@code @Configuration}
* class processing.
* <p>The default implementation is empty.
* @param importingClassMetadata annotation metadata of the importing class
* @param registry current bean definition registry
*/
default void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
}