具体分析流程如下图：
点进去@SpringBootApplication,发现其起作用的主要是有两个注解
1.@SpringBootConfiguration@SpringBootConfiguration //SpringBoot的配置
再点进去SpringBootConfiguration发现注解
@Configuration //spring配置类
再点进去@Configuration发现注解
@Component //说明这也是一个spring的组件
这一部分到这也就基本结束了（到头了）
接下来看
2.@EnableAutoConfiguration //自动配置点进去发现
1.@AutoConfigurationPackage //自动配置包点进去 下图为（自动配置包注册）
2.@Import({AutoConfigurationImportSelector.class}) //自动配置导入选择点进去发现getAutoConfigurationEntry(AnnotationMetadata annotationMetadata)
下面有段代码
//获取所有的配置 Listconfigurations = this.getCandidateConfigurations(annotationMetadata, attributes);
发现获取所有的配置有个getCandidateConfigurations方法，那我们再看看这个方法
// 获取候选的配置 protected ListgetCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) { List configurations = SpringFactoriesLoader.loadFactoryNames(this.getSpringFactoriesLoaderFactoryClass(), this.getBeanClassLoader()); Assert.notEmpty(configurations, "No auto configuration classes found in META-INF/spring.factories. If you are using a custom packaging, make sure that file is correct."); return configurations; }
getCandidateConfigurations 传入了一个annotationMetadata 这个东西就是当前这个注解标注在谁的头上，这是一个元数据
里面有一个loadFactoryNames方法，具体方法是干什么的可以自己看看传入的参数，其实这个方法兜兜转转只是为了加载所有的组件的全限类
// 所有资源加载到配置类中 Properties properties = PropertiesLoaderUtils.loadProperties(resource);
该方法下面还加了个断言
Assert.notEmpty(configurations, "No auto configuration classes found in META-INF/spring.factories. If you are using a custom packaging, make sure that file is correct.");
里面出现了个
META-INF/spring.factories //自动配置的核心文件
具体位置如下图所示
点开文件就发现各种配置
# Initializers org.springframework.context.ApplicationContextInitializer= org.springframework.boot.autoconfigure.SharedMetadataReaderFactoryContextInitializer, org.springframework.boot.autoconfigure.logging.ConditionEvaluationReportLoggingListener # Application Listeners org.springframework.context.ApplicationListener= org.springframework.boot.autoconfigure.BackgroundPreinitializer # Auto Configuration Import Listeners org.springframework.boot.autoconfigure.AutoConfigurationImportListener= org.springframework.boot.autoconfigure.condition.ConditionEvaluationReportAutoConfigurationImportListener # Auto Configuration Import Filters org.springframework.boot.autoconfigure.AutoConfigurationImportFilter= org.springframework.boot.autoconfigure.condition.OnBeanCondition, org.springframework.boot.autoconfigure.condition.OnClassCondition, org.springframework.boot.autoconfigure.condition.OnWebApplicationCondition # Auto Configure org.springframework.boot.autoconfigure.EnableAutoConfiguration= org.springframework.boot.autoconfigure.admin.SpringApplicationAdminJmxAutoConfiguration, org.springframework.boot.autoconfigure.aop.AopAutoConfiguration, org.springframework.boot.autoconfigure.amqp.RabbitAutoConfiguration, org.springframework.boot.autoconfigure.batch.BatchAutoConfiguration, org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration, org.springframework.boot.autoconfigure.cassandra.CassandraAutoConfiguration, org.springframework.boot.autoconfigure.context.ConfigurationPropertiesAutoConfiguration, org.springframework.boot.autoconfigure.context.LifecycleAutoConfiguration, org.springframework.boot.autoconfigure.context.MessageSourceAutoConfiguration, org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration, org.springframework.boot.autoconfigure.couchbase.CouchbaseAutoConfiguration, org.springframework.boot.autoconfigure.dao.PersistenceExceptionTranslationAutoConfiguration, org.springframework.boot.autoconfigure.data.cassandra.CassandraDataAutoConfiguration, org.springframework.boot.autoconfigure.data.cassandra.CassandraReactiveDataAutoConfiguration, org.springframework.boot.autoconfigure.data.cassandra.CassandraReactiveRepositoriesAutoConfiguration, org.springframework.boot.autoconfigure.data.cassandra.CassandraRepositoriesAutoConfiguration, org.springframework.boot.autoconfigure.data.couchbase.CouchbaseDataAutoConfiguration, org.springframework.boot.autoconfigure.data.couchbase.CouchbaseReactiveDataAutoConfiguration, org.springframework.boot.autoconfigure.data.couchbase.CouchbaseReactiveRepositoriesAutoConfiguration, org.springframework.boot.autoconfigure.data.couchbase.CouchbaseRepositoriesAutoConfiguration, org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchDataAutoConfiguration, org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchRepositoriesAutoConfiguration, org.springframework.boot.autoconfigure.data.elasticsearch.ReactiveElasticsearchRepositoriesAutoConfiguration, org.springframework.boot.autoconfigure.data.elasticsearch.ReactiveElasticsearchRestClientAutoConfiguration, org.springframework.boot.autoconfigure.data.jdbc.JdbcRepositoriesAutoConfiguration, org.springframework.boot.autoconfigure.data.jpa.JpaRepositoriesAutoConfiguration, org.springframework.boot.autoconfigure.data.ldap.LdapRepositoriesAutoConfiguration, org.springframework.boot.autoconfigure.data.mongo.MongoDataAutoConfiguration, org.springframework.boot.autoconfigure.data.mongo.MongoReactiveDataAutoConfiguration, org.springframework.boot.autoconfigure.data.mongo.MongoReactiveRepositoriesAutoConfiguration, org.springframework.boot.autoconfigure.data.mongo.MongoRepositoriesAutoConfiguration, org.springframework.boot.autoconfigure.data.neo4j.Neo4jDataAutoConfiguration, org.springframework.boot.autoconfigure.data.neo4j.Neo4jRepositoriesAutoConfiguration, org.springframework.boot.autoconfigure.data.solr.SolrRepositoriesAutoConfiguration, org.springframework.boot.autoconfigure.data.r2dbc.R2dbcDataAutoConfiguration, org.springframework.boot.autoconfigure.data.r2dbc.R2dbcRepositoriesAutoConfiguration, org.springframework.boot.autoconfigure.data.r2dbc.R2dbcTransactionManagerAutoConfiguration, org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration, org.springframework.boot.autoconfigure.data.redis.RedisReactiveAutoConfiguration, org.springframework.boot.autoconfigure.data.redis.RedisRepositoriesAutoConfiguration, org.springframework.boot.autoconfigure.data.rest.RepositoryRestMvcAutoConfiguration, org.springframework.boot.autoconfigure.data.web.SpringDataWebAutoConfiguration, org.springframework.boot.autoconfigure.elasticsearch.ElasticsearchRestClientAutoConfiguration, org.springframework.boot.autoconfigure.flyway.FlywayAutoConfiguration, org.springframework.boot.autoconfigure.freemarker.FreeMarkerAutoConfiguration, org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAutoConfiguration, org.springframework.boot.autoconfigure.gson.GsonAutoConfiguration, org.springframework.boot.autoconfigure.h2.H2ConsoleAutoConfiguration, org.springframework.boot.autoconfigure.hateoas.HypermediaAutoConfiguration, org.springframework.boot.autoconfigure.hazelcast.HazelcastAutoConfiguration, org.springframework.boot.autoconfigure.hazelcast.HazelcastJpaDependencyAutoConfiguration, org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration, org.springframework.boot.autoconfigure.http.codec.CodecsAutoConfiguration, org.springframework.boot.autoconfigure.influx.InfluxDbAutoConfiguration, org.springframework.boot.autoconfigure.info.ProjectInfoAutoConfiguration, org.springframework.boot.autoconfigure.integration.IntegrationAutoConfiguration, org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration, org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration, org.springframework.boot.autoconfigure.jdbc.JdbcTemplateAutoConfiguration, org.springframework.boot.autoconfigure.jdbc.JndiDataSourceAutoConfiguration, org.springframework.boot.autoconfigure.jdbc.XADataSourceAutoConfiguration, org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration, org.springframework.boot.autoconfigure.jms.JmsAutoConfiguration, org.springframework.boot.autoconfigure.jmx.JmxAutoConfiguration, org.springframework.boot.autoconfigure.jms.JndiConnectionFactoryAutoConfiguration, org.springframework.boot.autoconfigure.jms.activemq.ActiveMQAutoConfiguration, org.springframework.boot.autoconfigure.jms.artemis.ArtemisAutoConfiguration, org.springframework.boot.autoconfigure.jersey.JerseyAutoConfiguration, org.springframework.boot.autoconfigure.jooq.JooqAutoConfiguration, org.springframework.boot.autoconfigure.jsonb.JsonbAutoConfiguration, org.springframework.boot.autoconfigure.kafka.KafkaAutoConfiguration, org.springframework.boot.autoconfigure.availability.ApplicationAvailabilityAutoConfiguration, org.springframework.boot.autoconfigure.ldap.embedded.EmbeddedLdapAutoConfiguration, org.springframework.boot.autoconfigure.ldap.LdapAutoConfiguration, org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration, org.springframework.boot.autoconfigure.mail.MailSenderAutoConfiguration, org.springframework.boot.autoconfigure.mail.MailSenderValidatorAutoConfiguration, org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongoAutoConfiguration, org.springframework.boot.autoconfigure.mongo.MongoAutoConfiguration, org.springframework.boot.autoconfigure.mongo.MongoReactiveAutoConfiguration, org.springframework.boot.autoconfigure.mustache.MustacheAutoConfiguration, org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration, org.springframework.boot.autoconfigure.quartz.QuartzAutoConfiguration, org.springframework.boot.autoconfigure.r2dbc.R2dbcAutoConfiguration, org.springframework.boot.autoconfigure.rsocket.RSocketMessagingAutoConfiguration, org.springframework.boot.autoconfigure.rsocket.RSocketRequesterAutoConfiguration, org.springframework.boot.autoconfigure.rsocket.RSocketServerAutoConfiguration, org.springframework.boot.autoconfigure.rsocket.RSocketStrategiesAutoConfiguration, org.springframework.boot.autoconfigure.security.servlet.SecurityAutoConfiguration, org.springframework.boot.autoconfigure.security.servlet.UserDetailsServiceAutoConfiguration, org.springframework.boot.autoconfigure.security.servlet.SecurityFilterAutoConfiguration, org.springframework.boot.autoconfigure.security.reactive.ReactiveSecurityAutoConfiguration, org.springframework.boot.autoconfigure.security.reactive.ReactiveUserDetailsServiceAutoConfiguration, org.springframework.boot.autoconfigure.security.rsocket.RSocketSecurityAutoConfiguration, org.springframework.boot.autoconfigure.security.saml2.Saml2RelyingPartyAutoConfiguration, org.springframework.boot.autoconfigure.sendgrid.SendGridAutoConfiguration, org.springframework.boot.autoconfigure.session.SessionAutoConfiguration, org.springframework.boot.autoconfigure.security.oauth2.client.servlet.OAuth2ClientAutoConfiguration, org.springframework.boot.autoconfigure.security.oauth2.client.reactive.ReactiveOAuth2ClientAutoConfiguration, org.springframework.boot.autoconfigure.security.oauth2.resource.servlet.OAuth2ResourceServerAutoConfiguration, org.springframework.boot.autoconfigure.security.oauth2.resource.reactive.ReactiveOAuth2ResourceServerAutoConfiguration, org.springframework.boot.autoconfigure.solr.SolrAutoConfiguration, org.springframework.boot.autoconfigure.task.TaskExecutionAutoConfiguration, org.springframework.boot.autoconfigure.task.TaskSchedulingAutoConfiguration, org.springframework.boot.autoconfigure.thymeleaf.ThymeleafAutoConfiguration, org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration, org.springframework.boot.autoconfigure.transaction.jta.JtaAutoConfiguration, org.springframework.boot.autoconfigure.validation.ValidationAutoConfiguration, org.springframework.boot.autoconfigure.web.client.RestTemplateAutoConfiguration, org.springframework.boot.autoconfigure.web.embedded.EmbeddedWebServerFactoryCustomizerAutoConfiguration, org.springframework.boot.autoconfigure.web.reactive.HttpHandlerAutoConfiguration, org.springframework.boot.autoconfigure.web.reactive.ReactiveWebServerFactoryAutoConfiguration, org.springframework.boot.autoconfigure.web.reactive.WebFluxAutoConfiguration, org.springframework.boot.autoconfigure.web.reactive.error.ErrorWebFluxAutoConfiguration, org.springframework.boot.autoconfigure.web.reactive.function.client.ClientHttpConnectorAutoConfiguration, org.springframework.boot.autoconfigure.web.reactive.function.client.WebClientAutoConfiguration, org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration, org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryAutoConfiguration, org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration, org.springframework.boot.autoconfigure.web.servlet.HttpEncodingAutoConfiguration, org.springframework.boot.autoconfigure.web.servlet.MultipartAutoConfiguration, org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration, org.springframework.boot.autoconfigure.websocket.reactive.WebSocketReactiveAutoConfiguration, org.springframework.boot.autoconfigure.websocket.servlet.WebSocketServletAutoConfiguration, org.springframework.boot.autoconfigure.websocket.servlet.WebSocketMessagingAutoConfiguration, org.springframework.boot.autoconfigure.webservices.WebServicesAutoConfiguration, org.springframework.boot.autoconfigure.webservices.client.WebServiceTemplateAutoConfiguration # Failure analyzers org.springframework.boot.diagnostics.FailureAnalyzer= org.springframework.boot.autoconfigure.data.redis.RedisUrlSyntaxFailureAnalyzer, org.springframework.boot.autoconfigure.diagnostics.analyzer.NoSuchBeanDefinitionFailureAnalyzer, org.springframework.boot.autoconfigure.flyway.FlywayMigrationScriptMissingFailureAnalyzer, org.springframework.boot.autoconfigure.jdbc.DataSourceBeanCreationFailureAnalyzer, org.springframework.boot.autoconfigure.jdbc.HikariDriverConfigurationFailureAnalyzer, org.springframework.boot.autoconfigure.r2dbc.ConnectionFactoryBeanCreationFailureAnalyzer, org.springframework.boot.autoconfigure.session.NonUniqueSessionRepositoryFailureAnalyzer # Template availability providers org.springframework.boot.autoconfigure.template.TemplateAvailabilityProvider= org.springframework.boot.autoconfigure.freemarker.FreeMarkerTemplateAvailabilityProvider, org.springframework.boot.autoconfigure.mustache.MustacheTemplateAvailabilityProvider, org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAvailabilityProvider, org.springframework.boot.autoconfigure.thymeleaf.ThymeleafTemplateAvailabilityProvider, org.springframework.boot.autoconfigure.web.servlet.JspTemplateAvailabilityProvider
结论:
springboot所有自动配置都是在启动的时候扫描并加载: spring.factories所有的自动配置类都在这里面，但是不一定生效，要判断条件是否成立，只要导入了对应的start，就有对应的启动器了，有了启动器，我们自动装配就会生效，然后就配置成功!
参考：狂神说
