Springboot第二章 springboot 自動配置原理
springboot 官方文件記錄了properties/yml 能寫的所有配置
1、自動配置原理:
1)Sprintboot 啟動的時候,載入住配置類,開啟自動配置功能,
@EnableAutoConfiguration
利用
@Import(AutoConfigurationImportSelector.class)
給容器匯入元件在第一章中有說過
然後AutoConfigurationImportSelector 主要是他的
public String[] selectImports(AnnotationMetadata annotationMetadata)
這個方法 selectImports返回一個數組,他的數組裡面都是類(元件)全限路徑
List<String> configurations = getCandidateConfigurations(annotationMetadata,
attributes);
getCandidateConfigurations 傳入了一個annotationMetadata 這個東西就是當前這個註解標註在誰的頭上,這是一個元資料
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; }
這個方法返回一個list ,它裡面有一個loadFactoryNames方法, 就是載入所有的元件的全限類 , 他這裡第二個引數是一個類載入器,第一個是一個型別,這個型別
protected Class<?> getSpringFactoriesLoaderFactoryClass() {
return EnableAutoConfiguration.class;
}
public static List<String> loadFactoryNames(Class<?> factoryClass, @Nullable ClassLoader classLoader) { String factoryClassName = factoryClass.getName(); return loadSpringFactories(classLoader).getOrDefault(factoryClassName, Collections.emptyList()); }
返回的是一個 loadSpringFactories 這個方法,傳入了一個class loader
Enumeration<URL> urls = (classLoader != null ?
classLoader.getResources(FACTORIES_RESOURCE_LOCATION) :
ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION));
result = new LinkedMultiValueMap<>();
這個getResources 獲取自動配置元件
public static final String FACTORIES_RESOURCE_LOCATION = "META-INF/spring.factories";
在這裡下面
從properties中獲取到EnableAutoConfiguration.class類(類名)對應的值,然後把他們新增在容器中
SpringFactoriesLoader.loadFactoryNames()
掃描所有jar包類路徑下 META-INF/spring.factories
把掃描到的這些檔案的內容包裝成properties物件
從properties中獲取到EnableAutoConfiguration.class類(類名)對應的值,然後把他們新增在容器中
# 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.CassandraReactiveDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraReactiveRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseReactiveDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseReactiveRepositoriesAutoConfiguration,\
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.MongoReactiveDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.mongo.MongoReactiveRepositoriesAutoConfiguration,\
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.RedisReactiveAutoConfiguration,\
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.flyway.FlywayAutoConfiguration,\
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.http.HttpMessageConvertersAutoConfiguration,\
org.springframework.boot.autoconfigure.http.codec.CodecsAutoConfiguration,\
org.springframework.boot.autoconfigure.influx.InfluxDbAutoConfiguration,\
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.groovy.template.GroovyTemplateAutoConfiguration,\
org.springframework.boot.autoconfigure.jersey.JerseyAutoConfiguration,\
org.springframework.boot.autoconfigure.jooq.JooqAutoConfiguration,\
org.springframework.boot.autoconfigure.jsonb.JsonbAutoConfiguration,\
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.mongo.embedded.EmbeddedMongoAutoConfiguration,\
org.springframework.boot.autoconfigure.mongo.MongoAutoConfiguration,\
org.springframework.boot.autoconfigure.mongo.MongoReactiveAutoConfiguration,\
org.springframework.boot.autoconfigure.mustache.MustacheAutoConfiguration,\
org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration,\
org.springframework.boot.autoconfigure.quartz.QuartzAutoConfiguration,\
org.springframework.boot.autoconfigure.reactor.core.ReactorCoreAutoConfiguration,\
org.springframework.boot.autoconfigure.security.servlet.SecurityAutoConfiguration,\
org.springframework.boot.autoconfigure.security.servlet.UserDetailsServiceAutoConfiguration,\
org.springframework.boot.autoconfigure.security.servlet.SecurityFilterAutoConfiguration,\
org.springframework.boot.autoconfigure.security.reactive.ReactiveSecurityAutoConfiguration,\
org.springframework.boot.autoconfigure.security.reactive.ReactiveUserDetailsServiceAutoConfiguration,\
org.springframework.boot.autoconfigure.sendgrid.SendGridAutoConfiguration,\
org.springframework.boot.autoconfigure.session.SessionAutoConfiguration,\
org.springframework.boot.autoconfigure.security.oauth2.client.OAuth2ClientAutoConfiguration,\
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.client.RestTemplateAutoConfiguration,\
org.springframework.boot.autoconfigure.web.embedded.EmbeddedWebServerFactoryCustomizerAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.HttpHandlerAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.ReactiveWebServerFactoryAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.WebFluxAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.error.ErrorWebFluxAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.function.client.WebClientAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.HttpEncodingAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.MultipartAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration,\
org.springframework.boot.autoconfigure.websocket.reactive.WebSocketReactiveAutoConfiguration,\
org.springframework.boot.autoconfigure.websocket.servlet.WebSocketServletAutoConfiguration,\
org.springframework.boot.autoconfigure.websocket.servlet.WebSocketMessagingAutoConfiguration,\
org.springframework.boot.autoconfigure.webservices.WebServicesAutoConfiguration
每一個這樣的 xxxAutoConfiguration類都是容器中的一個元件,都加入到容器中;用他們來做自動配置;
3)、每一個自動配置類進行自動配置功能;
4)、以HttpEncodingAutoConfiguration(Http編碼自動配置)為例解釋自動配置原理;
@Configuration //表示這是一個配置類,以前編寫的配置檔案一樣,也可以給容器中新增元件
@EnableConfigurationProperties(HttpEncodingProperties.class) //啟動指定類的ConfigurationProperties功能;將配置檔案中對應的值和HttpEncodingProperties繫結起來;並把HttpEncodingProperties加入到ioc容器中
@ConditionalOnWebApplication //Spring底層@Conditional註解(Spring註解版),根據不同的條件,如果滿足指定的條件,整個配置類裡面的配置就會生效; 判斷當前應用是否是web應用,如果是,當前配置類生效
@ConditionalOnClass(CharacterEncodingFilter.class) //判斷當前專案有沒有這個類CharacterEncodingFilter;SpringMVC中進行亂碼解決的過濾器;
@ConditionalOnProperty(prefix = "spring.http.encoding", value = "enabled", matchIfMissing = true) //判斷配置檔案中是否存在某個配置 spring.http.encoding.enabled;如果不存在,判斷也是成立的
//即使我們配置檔案中不配置pring.http.encoding.enabled=true,也是預設生效的;
public class HttpEncodingAutoConfiguration {
//他已經和SpringBoot的配置檔案映射了
private final HttpEncodingProperties properties;
//只有一個有參構造器的情況下,引數的值就會從容器中拿
public HttpEncodingAutoConfiguration(HttpEncodingProperties properties) {
this.properties = properties;
}
@Bean //給容器中新增一個元件,這個元件的某些值需要從properties中獲取
@ConditionalOnMissingBean(CharacterEncodingFilter.class) //判斷容器沒有這個元件?
public CharacterEncodingFilter characterEncodingFilter() {
CharacterEncodingFilter filter = new OrderedCharacterEncodingFilter();
filter.setEncoding(this.properties.getCharset().name());
filter.setForceRequestEncoding(this.properties.shouldForce(Type.REQUEST));
filter.setForceResponseEncoding(this.properties.shouldForce(Type.RESPONSE));
return filter;
}
根據當前不同的條件判斷,決定這個配置類是否生效?
一但這個配置類生效;這個配置類就會給容器中新增各種元件;這些元件的屬性是從對應的properties類中獲取的,這些類裡面的每一個屬性又是和配置檔案繫結的;
5)、所有在配置檔案中能配置的屬性都是在xxxxProperties類中封裝者‘;配置檔案能配置什麼就可以參照某個功能對應的這個屬性類
@ConfigurationProperties(prefix = "spring.http.encoding") //從配置檔案中獲取指定的值和bean的屬性進行繫結
public class HttpEncodingProperties {
public static final Charset DEFAULT_CHARSET = Charset.forName("UTF-8");
精髓:
1)、SpringBoot啟動會載入大量的自動配置類
2)、我們看我們需要的功能有沒有SpringBoot預設寫好的自動配置類;
3)、我們再來看這個自動配置類中到底配置了哪些元件;(只要我們要用的元件有,我們就不需要再來配置了)
4)、給容器中自動配置類新增元件的時候,會從properties類中獲取某些屬性。我們就可以在配置檔案中指定這些屬性的值;
xxxxAutoConfigurartion:自動配置類;
給容器中新增元件
xxxxProperties:封裝配置檔案中相關屬性;
2、細節
1、@Conditional派生註解(Spring註解版原生的@Conditional作用)
作用:必須是@Conditional指定的條件成立,才給容器中新增元件,配置配裡面的所有內容才生效;
@Conditional擴充套件註解 | 作用(判斷是否滿足當前指定條件) |
---|---|
@ConditionalOnJava | 系統的java版本是否符合要求 |
@ConditionalOnBean | 容器中存在指定Bean; |
@ConditionalOnMissingBean | 容器中不存在指定Bean; |
@ConditionalOnExpression | 滿足SpEL表示式指定 |
@ConditionalOnClass | 系統中有指定的類 |
@ConditionalOnMissingClass | 系統中沒有指定的類 |
@ConditionalOnSingleCandidate | 容器中只有一個指定的Bean,或者這個Bean是首選Bean |
@ConditionalOnProperty | 系統中指定的屬性是否有指定的值 |
@ConditionalOnResource | 類路徑下是否存在指定資原始檔 |
@ConditionalOnWebApplication | 當前是web環境 |
@ConditionalOnNotWebApplication | 當前不是web環境 |
@ConditionalOnJndi | JNDI存在指定項 |
自動配置類必須在一定的條件下才能生效;
我們怎麼知道哪些自動配置類生效;
==我們可以通過啟用 debug=true屬性;來讓控制檯列印自動配置報告==,這樣我們就可以很方便的知道哪些自動配置類生效;
=========================
AUTO-CONFIGURATION REPORT
=========================
Positive matches:(自動配置類啟用的)
-----------------
DispatcherServletAutoConfiguration matched:
- @ConditionalOnClass found required class 'org.springframework.web.servlet.DispatcherServlet'; @ConditionalOnMissingClass did not find unwanted class (OnClassCondition)
- @ConditionalOnWebApplication (required) found StandardServletEnvironment (OnWebApplicationCondition)
Negative matches:(沒有啟動,沒有匹配成功的自動配置類)
-----------------
ActiveMQAutoConfiguration:
Did not match:
- @ConditionalOnClass did not find required classes 'javax.jms.ConnectionFactory', 'org.apache.activemq.ActiveMQConnectionFactory' (OnClassCondition)
AopAutoConfiguration:
Did not match:
- @ConditionalOnClass did not find required classes 'org.aspectj.lang.annotation.Aspect', 'org.aspectj.lang.reflect.Advice' (OnClassCondition)
debug=true 在properties 中配置