SpringBoot02-自动配置原理

自动配置原理

原理

SpringBoot启动时加载主配置类, 开启了自动配置功能@EnableAutoConfiguration.

@EnableAutoConfiguration作用

利用@Import({AutoConfigurationImportSelector.class})给容器导入了一些组件.

查看selectImports()方法

List<String> configurations = getCandidateConfigurations(annotationMetadata,attributes); //获取了候选的配置

getCandidateConﬁgurations()中

List<String> configurations = SpringFactoriesLoader.loadFactoryNames(getSpringFactoriesLoaderFactoryClass(), getBeanClassLoader());

loadFactoryNames()中

try {
            //扫描了所有jar包类路径下: META-INF/spring.factories
            Enumeration<URL> urls = classLoader != null ? classLoader.getResources("META-INF/spring.factories") : ClassLoader.getSystemResources("META-INF/spring.factories");
            ArrayList result = new ArrayList();
            //把扫描到的文件包装成properties对象
            while(urls.hasMoreElements()) {
                URL url = (URL)urls.nextElement();
                Properties properties = PropertiesLoaderUtils.loadProperties(new UrlResource(url));
                String factoryClassNames = properties.getProperty(factoryClassName);
                //从properties中获取到EnableAutoConfiguration.class类（类名）对应的值，然后把他们添加在容器 中
                result.addAll(Arrays.asList(StringUtils.commaDelimitedListToStringArray(factoryClassNames)));
            }

            return result;
        }

将类路径下 META-INF/spring.factories 里面配置的所有EnableAutoConﬁguration的值加入到了容器中

# 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.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.ElasticsearchRepositoriesAutoConfi guration,\ 
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,\ 
org.springframework.boot.autoconfigure.hazelcast.HazelcastAutoConfiguration,\ 
org.springframework.boot.autoconfigure.hazelcast.HazelcastJpaDependencyAutoConfiguration,\ 
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.flyway.FlywayAutoConfiguration,\ 
org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAutoConfiguration,\ 
org.springframework.boot.autoconfigure.jersey.JerseyAutoConfiguration,\ org.springframework.boot.autoconfigure.jooq.JooqAutoConfiguration,\ 
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.mobile.DeviceResolverAutoConfiguration,\ 
org.springframework.boot.autoconfigure.mobile.DeviceDelegatingViewResolverAutoConfiguration, \ 
org.springframework.boot.autoconfigure.mobile.SitePreferenceAutoConfiguration,\ 
org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongoAutoConfiguration,\ 
org.springframework.boot.autoconfigure.mongo.MongoAutoConfiguration,\ org.springframework.boot.autoconfigure.mustache.MustacheAutoConfiguration,\
org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration,\
org.springframework.boot.autoconfigure.reactor.ReactorAutoConfiguration,\ 
org.springframework.boot.autoconfigure.security.SecurityAutoConfiguration,\ 
org.springframework.boot.autoconfigure.security.SecurityFilterAutoConfiguration,\ 
org.springframework.boot.autoconfigure.security.FallbackWebSecurityAutoConfiguration,\ 
org.springframework.boot.autoconfigure.security.oauth2.OAuth2AutoConfiguration,\ 
org.springframework.boot.autoconfigure.sendgrid.SendGridAutoConfiguration,\ 
org.springframework.boot.autoconfigure.session.SessionAutoConfiguration,\ 
org.springframework.boot.autoconfigure.social.SocialWebAutoConfiguration,\ 
org.springframework.boot.autoconfigure.social.FacebookAutoConfiguration,\ 
org.springframework.boot.autoconfigure.social.LinkedInAutoConfiguration,\ 
org.springframework.boot.autoconfigure.social.TwitterAutoConfiguration,\ 
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.DispatcherServletAutoConfiguration,\ 
org.springframework.boot.autoconfigure.web.EmbeddedServletContainerAutoConfiguration,\ 
org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration,\ 
org.springframework.boot.autoconfigure.web.HttpEncodingAutoConfiguration,\ 
org.springframework.boot.autoconfigure.web.HttpMessageConvertersAutoConfiguration,\ 
org.springframework.boot.autoconfigure.web.MultipartAutoConfiguration,\ 
org.springframework.boot.autoconfigure.web.ServerPropertiesAutoConfiguration,\ 
org.springframework.boot.autoconfigure.web.WebClientAutoConfiguration,\ 
org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration,\ 
org.springframework.boot.autoconfigure.websocket.WebSocketAutoConfiguration,\ 
org.springframework.boot.autoconfigure.websocket.WebSocketMessagingAutoConfiguration,\ 
org.springframework.boot.autoconfigure.webservices.WebServicesAutoConfiguratio

每一个这样的xxxAutoConfiguration类都是容器中的一个组件, 都加入到容器中, 用他们来做自动配置.

每个自动配置类进入容器中后, 进行自动配置功能.

以HttpEncodingAutoConfiguration为例解释自动配置原理

@Configuration //表示这是一个配置类
/*
 * 启动指定类的 ConfigurationProperties功能；将配置文件中对应的值和HttpEncodingProperties绑定起来；
 * 并把 HttpEncodingProperties加入到ioc容器中.
*/
@EnableConfigurationProperties(HttpEncodingProperties.class)
@ConditionalOnWebApplication //判断当前应用是否是web应用, 如果是, 当前配置类生效 
/*
 * 判断当前项目有没有这个类
 * CharacterEncodingFilter: SpringMVC中进行乱码解决的过滤器
*/
@ConditionalOnClass(CharacterEncodingFilter.class)
/*
 * 判断配置文件中是否存在某个配置
*/
@ConditionalOnProperty(prefix = "spring.http.encoding", value = "enabled", matchIfMissing = true) //即使我们配置文件中不配置pring.http.encoding.enabled=true，也是默认生效的；
public class HttpEncodingAutoConfiguration {

    private final HttpEncodingProperties properties;

    //只有一个有参构造器的情况下，参数的值就会从容器中拿
    public HttpEncodingAutoConfiguration(HttpEncodingProperties properties) {
        this.properties = properties;
    }

    //给容器中添加一个组件，这个组件的某些值需要从properties中获取
    @Bean
    @ConditionalOnMissingBean(CharacterEncodingFilter.class) //判断容器没有这个组件
    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;
    }

根据当前不同的条件判断, 觉得这个配置类是否生效.
一旦该配置类生效, 就会给容器添加各种组件, 这些组件的属性是从对应的properties类中获取的，这些类里面的每一个属性又是和配置文件绑定的.

所有在配置文件中能配置的属性都是在xxxxProperties类中封装的, 配置文件能配置什么就可以参照某个功能对应的这个属性类.

@ConfigurationProperties(prefix = "spring.http.encoding")
public class HttpEncodingProperties {

    public static final Charset DEFAULT_CHARSET = Charset.forName("UTF-8");

    private Charset charset = DEFAULT_CHARSET;

    private Boolean force;

    private Boolean forceRequest;

    private Boolean forceResponse;

    ......

总结
1. SpringBoot启动时会加载大量的自动配置类.
2. 我们看我们需要的功能有没有被SpringBoot写入默认的自动配置类.
3. 我们再来看这个自动配置类中到底配置了哪些组件(只要我们要用的组件有, 我们就不需要再来配置了)
4. 给容器中自动配置类添加组件的时候, 会从properties类中获取某些属性, 我们就可以在配置文件中指定这些属性的值.

细节

@Conditional派生注解
自动配置类只有在一定条件下才能生效
1. 在application.properties/yml中启用debug=true属性, 来让控制台打印自动配置报告, 这样就可以很方便的知道哪些自动配置类生效.

posted @ 2020-05-11 21:04 yellowstreak 阅读(235) 评论(0) 编辑收藏举报

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SpringBoot02-自动配置原理

自动配置原理

原理

细节

公告