spring boot 自动配置
来看下 spring boot中自动配置的注解
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@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 {};
}
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再来看下， @enableautoconfiguration 是怎么处理自动配置的呢？
注意到@import(enableautoconfigurationimportselector.class)
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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;
}
}
}
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再来看下 autoconfigurationimportselector ，主要是 接口的 importselector 的实现
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@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);
}
}
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看下 spring.factories 文件
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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,\\
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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
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@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 {
}
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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
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@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;
}
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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快网idc。
原文链接：https://www.jianshu.com/p/7261521394e7
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