配置文件加载位置

SpringBoot会从这四个位置全部加载主配置文件；互补配置；

外部配置加载顺序

自动配置原理

1、自动配置原理：

1）、SpringBoot启动的时候加载主配置类，开启了自动配置功能==@EnableAutoConfiguration==

2）、@EnableAutoConfiguration 作用：

利用EnableAutoConfigurationImportSelector给容器中导入一些组件

可以查看selectImports()方法的内容；

List<String> configurations = getCandidateConfigurations(annotationMetadata, attributes);获取候选的配置

将 类路径下 META-INF/spring.factories 里面配置的所有EnableAutoConfiguration的值加入到了容器中；

# Auto Configureorg.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.cloud.CloudAutoConfiguration,\org.springframework.boot.autoconfigure.context.ConfigurationPropertiesAutoConfiguration,\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.CassandraRepositoriesAutoConfiguration,\org.springframework.boot.autoconfigure.data.couchbase.CouchbaseDataAutoConfiguration,\org.springframework.boot.autoconfigure.data.couchbase.CouchbaseRepositoriesAutoConfiguration,\org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchAutoConfiguration,\org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchDataAutoConfiguration,\org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchRepositoriesAutoConfiguration,\org.springframework.boot.autoconfigure.data.jpa.JpaRepositoriesAutoConfiguration,\org.springframework.boot.autoconfigure.data.ldap.LdapDataAutoConfiguration,\org.springframework.boot.autoconfigure.data.ldap.LdapRepositoriesAutoConfiguration,\org.springframework.boot.autoconfigure.data.mongo.MongoDataAutoConfiguration,\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.redis.RedisAutoConfiguration,\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.jest.JestAutoConfiguration,\org.springframework.boot.autoconfigure.freemarker.FreeMarkerAutoConfiguration,\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.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.flyway.FlywayAutoConfiguration,\org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAutoConfiguration,\org.springframework.boot.autoconfigure.jersey.JerseyAutoConfiguration,\org.springframework.boot.autoconfigure.jooq.JooqAutoConfiguration,\org.springframework.boot.autoconfigure.kafka.KafkaAutoConfiguration,\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.mobile.DeviceResolverAutoConfiguration,\org.springframework.boot.autoconfigure.mobile.DeviceDelegatingViewResolverAutoConfiguration,\org.springframework.boot.autoconfigure.mobile.SitePreferenceAutoConfiguration,\org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongoAutoConfiguration,\org.springframework.boot.autoconfigure.mongo.MongoAutoConfiguration,\org.springframework.boot.autoconfigure.mustache.MustacheAutoConfiguration,\org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration,\org.springframework.boot.autoconfigure.reactor.ReactorAutoConfiguration,\org.springframework.boot.autoconfigure.security.SecurityAutoConfiguration,\org.springframework.boot.autoconfigure.security.SecurityFilterAutoConfiguration,\org.springframework.boot.autoconfigure.security.FallbackWebSecurityAutoConfiguration,\org.springframework.boot.autoconfigure.security.oauth2.OAuth2AutoConfiguration,\org.springframework.boot.autoconfigure.sendgrid.SendGridAutoConfiguration,\org.springframework.boot.autoconfigure.session.SessionAutoConfiguration,\org.springframework.boot.autoconfigure.social.SocialWebAutoConfiguration,\org.springframework.boot.autoconfigure.social.FacebookAutoConfiguration,\org.springframework.boot.autoconfigure.social.LinkedInAutoConfiguration,\org.springframework.boot.autoconfigure.social.TwitterAutoConfiguration,\org.springframework.boot.autoconfigure.solr.SolrAutoConfiguration,\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.DispatcherServletAutoConfiguration,\org.springframework.boot.autoconfigure.web.EmbeddedServletContainerAutoConfiguration,\org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration,\org.springframework.boot.autoconfigure.web.HttpEncodingAutoConfiguration,\org.springframework.boot.autoconfigure.web.HttpMessageConvertersAutoConfiguration,\org.springframework.boot.autoconfigure.web.MultipartAutoConfiguration,\org.springframework.boot.autoconfigure.web.ServerPropertiesAutoConfiguration,\org.springframework.boot.autoconfigure.web.WebClientAutoConfiguration,\org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration,\org.springframework.boot.autoconfigure.websocket.WebSocketAutoConfiguration,\org.springframework.boot.autoconfigure.websocket.WebSocketMessagingAutoConfiguration,\org.springframework.boot.autoconfigure.webservices.WebServicesAutoConfiguration

每一个这样的 xxxAutoConfiguration类都是容器中的一个组件，都加入到容器中；用他们来做自动配置；

3）、每一个自动配置类进行自动配置功能；

4）、以HttpEncodingAutoConfiguration（Http编码自动配置）为例解释自动配置原理；

根据当前不同的条件判断，决定这个配置类是否生效？

一旦这个配置类生效；这个配置类就会给容器中添加各种组件；这些组件的属性是从对应的properties类中获取的，这些类里面的每一个属性又是和配置文件绑定的；

精髓：

​1）、SpringBoot启动会加载大量的自动配置类

​2）、我们看我们需要的功能有没有SpringBoot默认写好的自动配置类；

​3）、我们再来看这个自动配置类中到底配置了哪些组件；（只要我们要用的组件有，我们就不需要再来配置了）

​4）、给容器中自动配置类添加组件的时候，会从properties类中获取某些属性。我们就可以在配置文件中指定这些属性的值；

xxxxAutoConfigurartion：自动配置类；

给容器中添加组件

xxxxProperties:封装配置文件中相关属性；

2、细节

1、@Conditional派生注解（Spring注解版原生的@Conditional作用）

作用：必须是@Conditional指定的条件成立，才给容器中添加组件，配置配里面的所有内容才生效；

自动配置类必须在一定的条件下才能生效；

我们怎么知道哪些自动配置类生效；

==我们可以通过启用 debug=true属性；来让控制台打印自动配置报告==，这样我们就可以很方便的知道哪些自动配置类生效；