一、准备工作

1、导入spring-context依赖

<dependency><groupId>org.springframework</groupId><artifactId>spring-context</artifactId><version>5.2.22.RELEASE</version>
</dependency>

2、创建实体类Red、Blue、Yellow

public class Red {}
public class Blue {}
public class Yellow {}

二、注解使用

1、创建BeanConfig配置类

import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;//@Import(Red.class)
@Import({Red.class, Yellow.class, Blue.class})
@Configuration
public class BeansConfig {}

2、开始测试

public static void main(String[] args) {AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(BeansConfig.class);String[] names = context.getBeanDefinitionNames();for (String name:names) {System.out.println(name);}/*** @import注入bean的名称为：全类名* 包路径.Red* 包路径.Yellow* 包路径.Blue*/
}

三、ImportSelector

1、创建ColorSelector

import org.springframework.context.annotation.ImportSelector;
import org.springframework.core.type.AnnotationMetadata;public class ColorSelector implements ImportSelector {@Overridepublic String[] selectImports(AnnotationMetadata importingClassMetadata) {// 这里可以通过AnnotationMetadata处理业务逻辑，为了演示我们就尽量简单着来了return new String[]{Red.class.getName(), Blue.class.getName(), Yellow.class.getName()};}}

2、配置到@Import中

import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;//@Import({Red.class, Yellow.class, Blue.class})
@Import(ColorSelector.class)
@Configuration
public class BeansConfig {}

3、重新测试，结果一致

四、ImportBeanDefinitionRegistrar

1、创建ColorRegistrar

import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.RootBeanDefinition;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.type.AnnotationMetadata;public class ColorRegistrar implements ImportBeanDefinitionRegistrar {@Overridepublic void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {// 如果red没有注入，则手动注入if(!registry.containsBeanDefinition(Red.class.getName())){RootBeanDefinition red = new RootBeanDefinition(Red.class);registry.registerBeanDefinition("red",red);}// 如果blue没有注入，则手动注入if(!registry.containsBeanDefinition(Blue.class.getName())){RootBeanDefinition blue = new RootBeanDefinition(Blue.class);registry.registerBeanDefinition("blue",blue);}// 如果yellow没有注入，则手动注入if(!registry.containsBeanDefinition(Yellow.class.getName())){RootBeanDefinition yellow = new RootBeanDefinition(Yellow.class);registry.registerBeanDefinition("yellow",yellow);}}}

2、配置到@Import中

import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;//@Import(ColorSelector.class)
@Import(ColorRegistrar.class)
@Configuration
public class BeansConfig {}

3、再次测试，结果一致

三、总结分析

本章主要学习了，使用@Import注解注入Bean的三种方式。《参考资料》