SpringBoot自动配置之@Import

前言

@Enable*底层依赖于@Import注解导入一些类，使用@Import导入的类会被Spring加载到IOC容器中。而@Import提供4种用法。

@import的4种用法

1.直接导入Bean，即直接导入实体类的class文件：@Import（User.class)

@Import(User.class)
@SpringBootApplication
public class SpringbootEnableApplication {

    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(SpringbootEnableApplication.class, args);

        User user = context.getBean(User.class);
        System.out.println(user);
    }
}

2.导入配置类
我的配置类文件：

package cs.yangtze.springboot_enable_other.config;

import cs.yangtze.springboot_enable_other.entity.Role;
import cs.yangtze.springboot_enable_other.entity.User;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

/**
 * @Version 1.0
 * @Author:cyl
 * @Date:2022/8/10
 * @Content:
 */
//@Configuration
public class UserConfig {

    @Bean
    public User user(){
        return new User();
    }

    @Bean
    public Role role(){
        return new Role();
    }
}

@Import(UserConfig.class)
@SpringBootApplication
public class SpringbootEnableApplication {
    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(SpringbootEnableApplication.class, args);

        User user = context.getBean(User.class);
        System.out.println(user);

        Role role =context.getBean(Role.class);
        System.out.println(role);
    }
}

3.导入ImportSelector实现类，一般用于加载配置文件中的类。
我的ImportSelector实现类：

package cs.yangtze.springboot_enable_other.config;

import org.springframework.context.annotation.ImportSelector;
import org.springframework.core.type.AnnotationMetadata;

/**
 * @Version 1.0
 * @Author:cyl
 * @Date:2022/8/12
 * @Content:
 */
public class MyImportSelect implements ImportSelector {
    @Override
    public String[] selectImports(AnnotationMetadata importingClassMetadata) {
        return new String[]{"cs.yangtze.springboot_enable_other.entity.Role",
                "cs.yangtze.springboot_enable_other.entity.User"};
    }
}

@Import(MyImportSelect.class)
@SpringBootApplication
public class SpringbootEnableApplication {

    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(SpringbootEnableApplication.class, args);
        User user = context.getBean(User.class);
        System.out.println(user);

        Role role =context.getBean(Role.class);
        System.out.println(role);

    }
}

4.导入ImportBeanDefinitionRegistrar实现类。
我的实现类：

package cs.yangtze.springboot_enable_other.config;

import cs.yangtze.springboot_enable_other.entity.Role;
import cs.yangtze.springboot_enable_other.entity.User;
import org.springframework.beans.factory.support.AbstractBeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.BeanNameGenerator;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.type.AnnotationMetadata;

/**
 * @Version 1.0
 * @Author:cyl
 * @Date:2022/8/12
 * @Content:
 */
public class MyImportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar{
    @Override
    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry, BeanNameGenerator importBeanNameGenerator) {

        AbstractBeanDefinition beanDefinition = BeanDefinitionBuilder.rootBeanDefinition(User.class).getBeanDefinition();
        registry.registerBeanDefinition("user",beanDefinition);

        AbstractBeanDefinition beanDefinition2 = BeanDefinitionBuilder.rootBeanDefinition(Role.class).getBeanDefinition();
        registry.registerBeanDefinition("role",beanDefinition2);

    }
}

@Import(MyImportBeanDefinitionRegistrar.class)
@SpringBootApplication
public class SpringbootEnableApplication {

    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(SpringbootEnableApplication.class, args);
        Object user = context.getBean("user");
        System.out.println(user);

        Object role =context.getBean("role");
        System.out.println(role);
    }
}

总结

以上就是Import的四种用法，我个人是用的两个模块，其中一个模块导入另一个模块中的文件，下面是我的目录结构：
我都是用的该模块下的启动类，注意还要在此模块中的pom文件里导入另一个模块的依赖