SpringBoot入门基础

Posted 2021-06-26 吴二喵

一、自动配置特性

二、SpringBootApplication

@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan(excludeFilters = { @Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class),
@Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) })
public @interface SpringBootApplication {

1、SpringBootConfiguration

@Configuration，代表当前是一个配置类

2、@ComponentScan

指定扫描哪些，spring注解
3、@EnableAutoConfiguration
由下面两个注解合成
@AutoConfigurationPackage
@Import(AutoConfigurationImportSelector.class)
public @interface EnableAutoConfiguration {

3.1@AutoConfigurationPackage
@Import(AutoConfigurationPackages.Registrar.class)//给容器中导入一个组件
//利用registar给容器导入一系列组件，将指定的一个报下的所有组件导入进来
//所以默认导入application所在包下所有组件
public @interface AutoConfigurationPackage {

***@Import的高级用法

3.2@Import(AutoConfigurationImportSelector.class)
A利用AutoConfigurationEntry autoConfigurationEntry = getAutoConfigurationEntry(annotationMetadata)
给容器中批量导入一些组件
B.利用List configurations = getCandidateConfigurations(annotationMetadata, attributes);
获取所有需要导入到的后续配置
C.利用工厂加载得到所有的组件
Map<String, List> loadSpringFactories(@Nullable ClassLoader classLoader)
D.从META-INF/spring.factories位置来加载一个文件，默认扫描我们当前系统里面所有META-INF/spring.factories位置的文件
spring-boot-actuator-autoconfigure-2.3.0.RELEASE.jar包的配置文件里面写死了
springboot一启动就要给容器中加载的所有配置类（127个），虽然所有自动配置启动的时候默认全部加载，最终会按条件装配规则@Conditional按需配置。

# Auto Configure
# 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

3.3 修改默认配置

//给容器中加入了文件上传解析器
//给@Bean标注的方法传入了对象的参数，这个参数的值会从容器中找
//防止有些用户配置的文件上传解析器不符合规范
        @Bean
        @ConditionalOnBean({MultipartResolver.class})
        @ConditionalOnMissingBean(
            name = {"multipartResolver"}
        )
        public MultipartResolver multipartResolver(MultipartResolver resolver) {
            return resolver;
        }
    }

SpringBoot默认会在底层配好所有的组件。但过用户配置了以用户的优先。

    @Bean
    @ConditionalOnMissingBean
    public CharacterEncodingFilter characterEncodingFilter() {
        CharacterEncodingFilter filter = new OrderedCharacterEncodingFilter();
        filter.setEncoding(this.properties.getCharset().name());
        filter.setForceRequestEncoding(this.properties.shouldForce(org.springframework.boot.web.servlet.server.Encoding.Type.REQUEST));
        filter.setForceResponseEncoding(this.properties.shouldForce(org.springframework.boot.web.servlet.server.Encoding.Type.RESPONSE));
        return filter;
    }

总结：
SpringBoot先加载所有的自动配置类 xxxAutoConfiguration
每个自动配置类按照条件进行生效，默认都会绑定配置文件指定的值 xxxProperties里面拿，与xxxProperties配置文件进行了绑定
生效的配置类就会给容器中装配很多组件
只要容器中有这些组件，相当于这些功能就有了。
只要用户自己配置，就以用户的优先
定制化配置的方式：
1、用户直接自己@Bean替换底层的组件
2、用户去看这个组件获取的配置文件什么值进行相应的修改

xxxAutoConfiguration—>组件---->xxxPropertie里面拿值—>application.properties

3.4 最佳实践
1、引入场景依赖 xxx-starter
2、查看自动配置了哪些（选做）
applicaiton.properties中开debug=true