SpringBoot学习笔记

SpringBoot

项目中引入依赖可以从父工程spring-boot-starter-parent继承，无需指定版本号，如果需要覆盖父工程中的版本，只需在当前工程的properties重写父工程的版本号即可（就近优先原则），比如

# 修改springboot父工程mysql版本号
<properties>
	<mysql.version>5.1.43</mysql.version>
</properties>

• 自动配置

• 默认包结构

  • 主程序所在包同级极其所有子包都会加载到IOC容器内，无需配置包扫描

  • 如果想要改变扫描路径，需要使用@SpringBootApplication(scanBasePackages="com.xxx")或者使用@ComponentScan指定扫描路径

    @SpringBootApplication等同于
    @SpringBootConfiguration
    @EnableAutoConfiguration
    @ComponentScan

• 各种配置都有默认值

  • 配置最终都是映射到对应的java类上
  • 按需加载自动配置
  • springboot所有的自动配置功能都在spring-boot-autoconfigure包

常用注解

1. @Configuration标识这个类是一个配置类

   • Full模式：proxyBeanMethods = true表示创建的配置类为代理对象，springboot总会检查容器中是否有配置类中的组件，能够解决依赖问题
   • Lite模式：proxyBeanMethods = false表示创建的配置类的类型为配置类本身，而不是配置类的代理类，当明确配置类中的组件不存在依赖关系可以使用Lite模式，减少检查组件是否在容器中的性能开销，从而加快springboot启动的速度

2. @Bean 创建一个组件

3. @Import导入组件

   • 向容器中导入组件，组件的名字默认为全类名@Import({User.class,Pet.class})接受一个数组

4. @Conditional 条件装配：满足Conditional指定的条件，则进行组件注入

   • @ConditionalOnBean 可以加在方法和类上
   • @ConditionalOnMissingBean 可以加在方法和类上

5. @ImportResource作用是将配置文件作为一个资源导入到容器中

   • @ImportResource("classpath:beans.xml")

配置绑定

方式一：@Component+@ConfigurationProperties(prefix = "前缀")将配置文件中的值与对象实例绑定

方式二：@EnableConfigurationProperties(xxx.class)+@ConfigurationProperties(prefix = "前缀")，xxx表示要开启配置绑定的类

自动装配原理

• @SpringBootConfiguration 相当于@Configuration，是一个配置类

• @EnableAutoConfiguration

  • @AutoConfigurationPackage

    • @Import(AutoConfigurationPackages.Registrar.class) 给容器中导入一个组件，利用Registrar给容器导入一系列组件，将指定的一个包下的所有组件导入进来，即Application所在的包下

  • @Import(AutoConfigurationImportSelector.class)

    1、利用getAutoConfigurationEntry(annotationMetadata);给容器中批量导入一些组件
    2、调用List<String> configurations = getCandidateConfigurations(annotationMetadata, attributes)获取到所有需要导入到容器中的配置类
    3、利用工厂加载 Map<String, List<String>> loadSpringFactories(@Nullable ClassLoader classLoader)；得到所有的组件
    4、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-autoconfigure-2.3.4.RELEASE.jar包里面也有META-INF/spring.factories
        

    文件里面写死了spring-boot一启动就要给容器中加载的所有配置类
    spring-boot-autoconfigure-2.3.4.RELEASE.jar/META-INF/spring.factories
    # 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

    按需开启自动配置项

    虽然我们127个场景的所有自动配置启动的时候默认全部加载。xxxxAutoConfiguration 按照条件装配规则（@Conditional），最终会按需配置。

修改默认配置

        @Bean
		@ConditionalOnBean(MultipartResolver.class)  //容器中有这个类型组件
		@ConditionalOnMissingBean(name = DispatcherServlet.MULTIPART_RESOLVER_BEAN_NAME) //容器中没有这个名字 multipartResolver 的组件
		public MultipartResolver multipartResolver(MultipartResolver resolver) {
            //给@Bean标注的方法传入了对象参数，这个参数的值就会从容器中找。
            //SpringMVC multipartResolver。防止有些用户配置的文件上传解析器不符合规范
			// Detect if the user has created a MultipartResolver but named it incorrectly
			return resolver;
		}
给容器中加入了文件上传解析器；

SpringBoot默认会在底层配好所有的组件。但是如果用户自己配置了以用户的优先

• SpringBoot先加载所有的自动配置类 xxxxxAutoConfiguration

• 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。xxxxProperties里面拿。xxxProperties和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

• 定制化配置

• • 用户直接自己@Bean替换底层的组件
  • 用户去看这个组件是获取的配置文件什么值就去修改。

xxxxxAutoConfiguration —> 组件 —> xxxxProperties里面拿值 —-> application.properties