前置
如何动态导入Bean?
@Import注解的作用
- 通常用于导入@Configuration类型
- 导入普通的Bean
- 实现ImportSelector类型
- 实现ImportBeanDefinitionRegistrar
/**
* Indicates one or more <em>component classes</em> to import — typically
* {@link Configuration @Configuration} classes.
*
* <p>Provides functionality equivalent to the {@code <import/>} element in Spring XML.
* Allows for importing {@code @Configuration} classes, {@link ImportSelector} and
* {@link ImportBeanDefinitionRegistrar} implementations, as well as regular component
* classes (as of 4.2; analogous to {@link AnnotationConfigApplicationContext#register}).
*
* <p>{@code @Bean} definitions declared in imported {@code @Configuration} classes should be
* accessed by using {@link org.springframework.beans.factory.annotation.Autowired @Autowired}
* injection. Either the bean itself can be autowired, or the configuration class instance
* declaring the bean can be autowired. The latter approach allows for explicit, IDE-friendly
* navigation between {@code @Configuration} class methods.
*
* <p>May be declared at the class level or as a meta-annotation.
*
* <p>If XML or other non-{@code @Configuration} bean definition resources need to be
* imported, use the {@link ImportResource @ImportResource} annotation instead.
*
* @author Chris Beams
* @author Juergen Hoeller
* @since 3.0
* @see Configuration
* @see ImportSelector
* @see ImportBeanDefinitionRegistrar
* @see ImportResource
*/
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Import {
/**
* {@link Configuration @Configuration}, {@link ImportSelector},
* {@link ImportBeanDefinitionRegistrar}, or regular component classes to import.
*/
Class<?>[] value();
}
Demo
package com.dite;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.RootBeanDefinition;
import org.springframework.context.annotation.*;
import org.springframework.core.type.AnnotationMetadata;
import java.util.Arrays;
/**
* Create by dgx 2022/4/1 23:21
*/
@Import({Person.class,FruitConfiguration.class,SelectImportInstance.class,MyImportBeanDefinitionRegistrar.class})
public class ImportDemo {
public static void main(String[] args) {
AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(ImportDemo.class);
String[] beanDefinitionNames = context.getBeanDefinitionNames();
for (String beanDefinitionName : beanDefinitionNames) {
System.out.println(beanDefinitionName);
}
}
}
/**
* 普通类
*/
class Person{
}
@org.springframework.context.annotation.Configuration
class FruitConfiguration{
@Bean
Fruit fruit(){
return new Fruit();
}
}
class Fruit{
}
/**
* 通过实现ImportSelector 导入
*/
class SelectImportInstance implements ImportSelector{
public String[] selectImports(AnnotationMetadata importingClassMetadata) {
return new String[]{Bike.class.getName()};
}
}
class Bike{
}
/**
* 通过实现ImportSelector 导入
*/
class MyImportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar {
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
registry.registerBeanDefinition("plane",new RootBeanDefinition(Plane.class));
}
}
class Plane{
}
class BooK{
}
