ImportBeanDefinitionRegistrar方式实现Bean的动态装载

springboot中有两种方式实现bean的动态装载

• ImportSelector
• ImportBeanDefinitionRegistrar

ImportSelector在springboot自动装配原理相关文章中已经介绍过了，这里简单记录下ImportBeanDefinitionRegistrar实现bean的动态装载：1. 首先随便定义一个pojo:

package com.gupaoedu.springcloud.example.demo02;

public class HelloService {

}

2. 通过实现ImportBeanDefinitionRegistrar 来完成bean的装载：

package com.gupaoedu.springcloud.example.demo02;

import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.GenericBeanDefinition;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.type.AnnotationMetadata;

public class MyBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar {
    @Override
    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
        BeanDefinition beanDefinition = new GenericBeanDefinition();
        beanDefinition.setBeanClassName(HelloService.class.getName());
        registry.registerBeanDefinition("myhelloService", beanDefinition);
    }
}

3. 自定义注解EnableMyRegistrar，导入动态装载的配置类MyBeanDefinitionRegistrar

package com.gupaoedu.springcloud.example.demo02;

import org.springframework.context.annotation.Import;
import java.lang.annotation.*;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import(MyBeanDefinitionRegistrar.class)
public @interface EnableMyRegistrar {
}

4. springboot启动类类加上自定义注解EnableMyRegistrar

package com.gupaoedu.springcloud.example.springclouduserservice;

import com.gupaoedu.springcloud.example.demo02.EnableGpRegistrara;
import com.gupaoedu.springcloud.example.demo02.EnableMyRegistrar;
import com.gupaoedu.springcloud.example.demo02.HelloService;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ComponentScan;

@EnableMyRegistrar
//@EnableGpRegistrara
// 第三方包里面声明的feign接口，不在SpringBootApplication同级目录下，需要手动指定@FeignClient注解扫描包路径
//@EnableFeignClients(basePackages = "com.gupaoedu.example.clients")
@SpringBootApplication
public class SpringCloudUserServiceApplication {

    public static void main(String[] args) {

        ConfigurableApplicationContext contxt=SpringApplication.run(SpringCloudUserServiceApplication.class, args);
        System.out.println(contxt.getBean(HelloService.class));
        System.out.println(contxt.getBean("myhelloService"));
    }

}

运行查看结果