SPRINGBOOT02_自动配置原理入门Lombokdev-tools快速初始化boot项目

Posted 2022-02-24 所得皆惊喜

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文章目录

①. 整体查看主启动类
②. @SpringBootConfiguration
③. @ComponentScan
④. @EnableAutoConfiguration
⑤. Lombok
⑥. 最佳实践-dev-tools
⑦. 最佳实践-Spring Initailizr

①. 整体查看主启动类

①. 主启动类如下

@SpringBootApplication
public class MainApplication 
    public static void main(String[] args) 
        SpringApplication.run(MainApplication.class, args);

②. 重点分析
@SpringBootConfiguration @EnableAutoConfiguration @ComponentScan

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan(
    excludeFilters = @Filter(
    type = FilterType.CUSTOM,
    classes = TypeExcludeFilter.class
), @Filter(
    type = FilterType.CUSTOM,
    classes = AutoConfigurationExcludeFilter.class
)
)

②. @SpringBootConfiguration

①. 在SpringBootConfiguration中有一个注解@Configuration,标注这个注解的类就是一个配置类

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Configuration
public @interface SpringBootConfiguration 
    @AliasFor(
        annotation = Configuration.class
    )
    boolean proxyBeanMethods() default true;

②. @Configuration这个注解用于以JavaConfig的方式来定义配置类,可替换 xml 配置文件,被注解的类内部包含有一个或多个被@Bean注解的方法,这些方法将会被AnnotationConfigAppli cationContext或AnnotationConfig WebApplicationContext类进行扫描,并用于构建bean定义,初始化Spring容器。这也是SpringBoot中没有xml配置文件的原因,SpringBoot都是通过配置类的方式将Bean注入到SpringIOC的容器中

③. @ComponentScan

扫描标明了@SpringBootApplication的类或及其子包进行一个扫描

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Repeatable(ComponentScans.class)
public @interface ComponentScan

④. @EnableAutoConfiguration

①. 主要的代码如下

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@AutoConfigurationPackage
@Import(AutoConfigurationImportSelector.class)
public @interface EnableAutoConfiguration

②. @AutoConfigurationPackage: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(MainApplication所在的包下)
③. @Import(AutoConfigurationImportSelector.class)
(1). 利用getAutoConfigurationEntry(annotationMetadata);给容器中批量导入一些组件
(2). 调用List 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> 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
并不是所有的Bean都会被初始化,在配置类中使用Condition来加载满足条件的Bean

   public String[] selectImports(AnnotationMetadata annotationMetadata) 
       if (!this.isEnabled(annotationMetadata)) 
           return NO_IMPORTS;
        else 
           //(1). 利用getAutoConfigurationEntry(annotationMetadata);给容器中批量导入一些组件
           AutoConfigurationImportSelector.AutoConfigurationEntry autoConfigurationEntry =
           this.getAutoConfigurationEntry(annotationMetadata);
           return StringUtils.toStringArray(autoConfigurationEntry.getConfigurations());
       
   
   protected AutoConfigurationImportSelector.AutoConfigurationEntry getAutoConfigurationEntry(AnnotationMetadata annotationMetadata) 
      if (!this.isEnabled(annotationMetadata)) 
          return EMPTY_ENTRY;
       else 
          AnnotationAttributes attributes = this.getAttributes(annotationMetadata);
          //(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
          List<String> configurations = this.getCandidateConfigurations(annotationMetadata, attributes);
          configurations = this.removeDuplicates(configurations);
          Set<String> exclusions = this.getExclusions(annotationMetadata, attributes);
          this.checkExcludedClasses(configurations, exclusions);
          configurations.removeAll(exclusions);
          configurations = this.getConfigurationClassFilter().filter(configurations);
          this.fireAutoConfigurationImportEvents(configurations, exclusions);
          return new AutoConfigurationImportSelector.AutoConfigurationEntry(configurations, exclusions);
      
  
   protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) 
      List<String> 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;
  
  //(3). 利用工厂加载 Map<String, List<String>> loadSpringFactories(@Nullable ClassLoader 
  //classLoader)得到所有的组件
  public static List<String> loadFactoryNames(Class<?> factoryType, @Nullable ClassLoader classLoader) 
      String factoryTypeName = factoryType.getName();
      return (List)loadSpringFactories(classLoader).getOrDefault(factoryTypeName, Collections.emptyList());
  
  private static Map<String, List<String>> loadSpringFactories(@Nullable ClassLoader classLoader) 
     MultiValueMap<String, String> result = (MultiValueMap)cache.get(classLoader);
      if (result != null) 
          return result;
       else 
          try 
          //(4). 从META-INF/spring.factories位置来加载一个文件
          Enumeration<URL> urls = classLoader != null ? classLoader.getResources
          ("META-INF/spring.factories") : ClassLoader.getSystemResources("META-INF/spring.factories");
          LinkedMultiValueMap result = new LinkedMultiValueMap();

# 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(@Conditiona),最终会按需配置
# 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,\\
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