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";
Class[] exclude() default {};
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 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 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 {
Class[] value() default {};
String[] type() default {};
Class[] annotation() default {};
String[] name() default {};
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考高分网。
