• 008-Spring Boot @EnableAutoConfiguration深入分析、内部如何使用EnableAutoConfiguration


    一、EnableAutoConfiguration

    1、EnableAutoConfiguration原理

    springboot程序入口使用注解@SpringBootApplication,SpringBootApplication注解的定义如下

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

    头部有三个注解,

    @SpringBootConfiguration:表示是一个配置类

    @ComponentScan:自动扫描,

    @EnableAutoConfiguration:

    作用:从classpath中搜索所有META-INF/spring.factories配置文件,然后将其中org.springframework.boot.autoconfigure.EnableAutoConfiguration 的key对应的配置项加载到容器中。

    只有spring.boot.enableautoconfiguration 为true【默认为true】的时候,才启用自动配置

    关键点:1》、ImportSelector改接口的方法的返回值都会被纳入到spring容器管理中;2》、SpringFactoriesLoader该类可以从classpath中搜索所有的 META-INF/spring.factories配置文件,并读取配置,交由ImportSelector接口纳入spring处理

    1.5版本以前

    @Import(EnableAutoConfigurationImportSelector.class)
    public @interface EnableAutoConfiguration {

    查看EnableAutoConfigurationImportSelector 查看父类AutoConfigurationImportSelector

        public String[] selectImports(AnnotationMetadata annotationMetadata) {
            if (!isEnabled(annotationMetadata)) {
                return NO_IMPORTS;
            }
            try {
                AutoConfigurationMetadata autoConfigurationMetadata = AutoConfigurationMetadataLoader
                        .loadMetadata(this.beanClassLoader);
                AnnotationAttributes attributes = getAttributes(annotationMetadata);
                List<String> configurations = getCandidateConfigurations(annotationMetadata,
                        attributes);
                configurations = removeDuplicates(configurations);
                configurations = sort(configurations, autoConfigurationMetadata);
                Set<String> exclusions = getExclusions(annotationMetadata, attributes);
                checkExcludedClasses(configurations, exclusions);
                configurations.removeAll(exclusions);
                configurations = filter(configurations, autoConfigurationMetadata);
                fireAutoConfigurationImportEvents(configurations, exclusions);
                return configurations.toArray(new String[configurations.size()]);
            }
            catch (IOException ex) {
                throw new IllegalStateException(ex);
            }
        }
    View Code

    调用了getCandidateConfigurations

        protected List<String> getCandidateConfigurations(AnnotationMetadata metadata,
                AnnotationAttributes attributes) {
            List<String> configurations = SpringFactoriesLoader.loadFactoryNames(
                    getSpringFactoriesLoaderFactoryClass(), 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;
        }

    可以看到自定义包:found in META-INF/spring.factories

    在自定义包的src/main/resource/增加以上META-INF/spring.factories内容

    org.springframework.boot.autoconfigure.EnableAutoConfiguration=com.lhx.spring.springboot_enableauto_example.RunnableConfiguration

    然后这个包就可以自动被导入了。

    public @interface EnableAutoConfiguration {
    
        String ENABLED_OVERRIDE_PROPERTY = "spring.boot.enableautoconfiguration";
    
        /**
         * Exclude specific auto-configuration classes such that they will never be applied.
         * @return the classes to exclude
         */
        Class<?>[] exclude() default {};
    
        /**
         * Exclude specific auto-configuration class names such that they will never be
         * applied.
         * @return the class names to exclude
         * @since 1.3.0
         */
        String[] excludeName() default {};
    
    }

    1、ENABLED_OVERRIDE_PROPERTY 配置项:spring.boot.enableautoconfiguration  控制是否启用此注解,可在application.properties中配置。

        @Override
        protected boolean isEnabled(AnnotationMetadata metadata) {
            if (getClass().equals(EnableAutoConfigurationImportSelector.class)) {
                return getEnvironment().getProperty(
                        EnableAutoConfiguration.ENABLED_OVERRIDE_PROPERTY, Boolean.class,
                        true);
            }
            return true;
        }

    2、exclude、excludeName排除

    使用:@EnableAutoConfiguration(exclude=UserConfig.class)

    @EnableAutoConfiguration(excludeName= {"com.lhx.spring.springboot_enableauto_example.Role"})

    1.5版本以后

    Deprecated. as of 1.5 in favor of AutoConfigurationImportSelector

    DeferredImportSelector to handle auto-configuration. This class can also be subclassed if a custom variant of @EnableAutoConfiguration. is needed.

    这里可以看到其实1.5以后是将EnableAutoConfigurationImportSelector 向上提了一个类。

    二、spring boot 内部如何使用EnableAutoConfiguration

    找到jar:spring-boot-autoconfigure-1.5.9.RELEASE.jar

    查看META-INF,其中也存在spring.facetories文件。

    # Initializers
    org.springframework.context.ApplicationContextInitializer=
    org.springframework.boot.autoconfigure.SharedMetadataReaderFactoryContextInitializer,
    org.springframework.boot.autoconfigure.logging.AutoConfigurationReportLoggingInitializer
    
    # 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.OnClassCondition
    
    # 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.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
    
    # Failure analyzers
    org.springframework.boot.diagnostics.FailureAnalyzer=
    org.springframework.boot.autoconfigure.diagnostics.analyzer.NoSuchBeanDefinitionFailureAnalyzer,
    org.springframework.boot.autoconfigure.jdbc.DataSourceBeanCreationFailureAnalyzer,
    org.springframework.boot.autoconfigure.jdbc.HikariDriverConfigurationFailureAnalyzer
    
    # 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.JspTemplateAvailabilityProvider
    View Code

    示例:

    查看:org.springframework.boot.autoconfigure.gson包

    1.看META-INFO/spring.factories中存在

    2.查看类GsonAutoConfiguration

    @Configuration
    @ConditionalOnClass(Gson.class)
    public class GsonAutoConfiguration {
    
        @Bean
        @ConditionalOnMissingBean
        public Gson gson() {
            return new Gson();
        }
    
    }

    说明:Configuration是一个配置类,ConditionalOnClass(Gson.class)类存在才加载

     @ConditionalOnMissingBean,没有才装配,有就以个人装配为准

    代码地址:https://github.com/bjlhx15/spring-boot.git 中的 springboot-enable即可

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  • 原文地址:https://www.cnblogs.com/bjlhx/p/8338342.html
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