Spring Boot 自动配置

来看下 spring boot中自动配置的注解

@SuppressWarnings("deprecation")@Target(ElementType.TYPE)@Retention(RetentionPolicy.RUNTIME)@Documented@Inherited@AutoConfigurationPackage@Import(EnableAutoConfigurationImportSelector.class)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 {};}

exclude() 可以排除一些自动配置的内容

excludeName 通过名称排除自动配置内容

再来看下， @EnableAutoConfiguration 是怎么处理自动配置的呢？

注意到@Import(EnableAutoConfigurationImportSelector.class)

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

再来看下 AutoConfigurationImportSelector ，主要是 接口的 ImportSelector 的实现

@Override public String[] selectImports(AnnotationMetadata annotationMetadata) { if (!isEnabled(annotationMetadata)) { return NO_IMPORTS; } try { //1、 自动配置的元数据 spring-autocomfigure-metadata.properties // 自动配置的开启条件 AutoConfigurationMetadata autoConfigurationMetadata = AutoConfigurationMetadataLoader .loadMetadata(this.beanClassLoader); AnnotationAttributes attributes = getAttributes(annotationMetadata); // 获取设置的自动配置列表 spring.factories List<String> configurations = getCandidateConfigurations(annotationMetadata, attributes); configurations = removeDuplicates(configurations); configurations = sort(configurations, autoConfigurationMetadata); // 获取要排除的自动配置列表，可以通过 注解@EnableAutoConfiguration 的exclude和 // 配置文件设置 spring.autoconfigure.exclude key的值 Set<String> exclusions = getExclusions(annotationMetadata, attributes); checkExcludedClasses(configurations, exclusions); configurations.removeAll(exclusions); // 通过 spring-autocomfigure-metadata.properties ConditionOnClass 条件进行过滤 configurations = filter(configurations, autoConfigurationMetadata); fireAutoConfigurationImportEvents(configurations, exclusions); return configurations.toArray(new String[configurations.size()]); } catch (IOException ex) { throw new IllegalStateException(ex); } }

看下 spring.factories 文件

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,\

再看下 spring framework中 ConfigurationClassParser 的处理方式，会解析 @Import 里的接口 ImportSelector 返回的所有配置类,那是怎么配置的呢，如 JpaRepositoriesAutoConfiguration

@Configuration@ConditionalOnBean(DataSource.class)@ConditionalOnClass(JpaRepository.class)@ConditionalOnMissingBean({ JpaRepositoryFactoryBean.class, JpaRepositoryConfigExtension.class })@ConditionalOnProperty(prefix = "spring.data.jpa.repositories", name = "enabled", havingValue = "true", matchIfMissing = true)@Import(JpaRepositoriesAutoConfigureRegistrar.class)@AutoConfigureAfter(HibernateJpaAutoConfiguration.class)public class JpaRepositoriesAutoConfiguration {}

从上面可以看到，有很多的@ConditionalOn**的注解，我们来看下 ConditionEvaluator这个 条件计算器，会去计算出当前这个配置类 是否要开启，而这些 @ConditionalOn** 是依赖于 @Conditional 这个注解，如 @ConditionalOnBean 最终是通过 Condition 接口来作条件选择

@Target({ ElementType.TYPE, ElementType.METHOD })@Retention(RetentionPolicy.RUNTIME)@Documented@Conditional(OnBeanCondition.class)public @interface ConditionalOnBean { /** * The class type of bean that should be checked. The condition matches when any of * the classes specified is contained in the {@link ApplicationContext}. * @return the class types of beans to check */ Class<?>[] value() default {}; /** * The class type names of bean that should be checked. The condition matches when any * of the classes specified is contained in the {@link ApplicationContext}. * @return the class type names of beans to check */ String[] type() default {}; /** * The annotation type decorating a bean that should be checked. The condition matches * when any of the annotations specified is defined on a bean in the * {@link ApplicationContext}. * @return the class-level annotation types to check */ Class<? extends Annotation>[] annotation() default {}; /** * The names of beans to check. The condition matches when any of the bean names * specified is contained in the {@link ApplicationContext}. * @return the name of beans to check */ String[] name() default {}; /** * Strategy to decide if the application context hierarchy (parent contexts) should be * considered. * @return the search strategy */ SearchStrategy search() default SearchStrategy.ALL;}

Spring boot 的autoconfigure 是囊括了所有可以和spring 整合的项目，但大部分情况下，并不是所以的项目都会启用，通过 Condition和@Conditional 来判断条件

判断classPath 是否存在指定的类 @ConditionalOnClass

判断 ApplicationContext 中是否存在指定的 Bean @ConditionalOnBean

配置环境中是否存在特定的配置项 @ConditionalOnProperty

配置环境中指定的配置项是否存在指定的值

禁用配置

当前 也是可以禁用某些我们不想要的默认配置，如上面加载时说到，会排除一些配置(exclude)

设置 @EnableAutoConfiguration 的exclude 配置

在配置文件增加 spring.autoconfigure.exclude 配置

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。