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 {
@Override
public 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 {
@Override
public 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》