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
作者：David_jim
链接：https://www.jianshu.com/p/7261521394e7
来自 “ ITPUB博客 ” ，链接：https://blog.itpub.net/4383/viewspace-2815945/ ，如需转载，请注明出处，否则将追究法律责任。
请登录后发表评论
登录
全部评论
