SpringBoot自动配置原理

1、SpringBoot会自动扫描每一个jar包下的meta-INF/spring.factories文件，读取其中的内容并实例化

其中org.springframework.boot:spring-boot-autoconfigure中的spring.factories包含许多自动配置包

2、以RabbitAutoConfiguration为例

//表明这是一个配置类
@Configuration(
        
        proxyBeanMethods = false
)

@ConditionalOnClass({RabbitTemplate.class, Channel.class})


@EnableConfigurationProperties({RabbitProperties.class})

@import({RabbitAnnotationDrivenConfiguration.class, RabbitStreamConfiguration.class})




public class RabbitAutoConfiguration {
    public RabbitAutoConfiguration() {
    }

    @Configuration(
            proxyBeanMethods = false
    )
    
    @ConditionalOnClass({RabbitMessagingTemplate.class})
    
    @ConditionalOnMissingBean({RabbitMessagingTemplate.class})
    
    @import({RabbitAutoConfiguration.RabbitTemplateConfiguration.class})
    protected static class MessagingTemplateConfiguration {
        protected MessagingTemplateConfiguration() {
        }

        @Bean
        
        @ConditionalOnSingleCandidate(RabbitTemplate.class)
        public RabbitMessagingTemplate rabbitMessagingTemplate(RabbitTemplate rabbitTemplate) {
            return new RabbitMessagingTemplate(rabbitTemplate);
        }
    }