springboot自动配置原理（高低版本比较）spring.factories文件的作用

@SpringBootApplication
public class SpringSecurityApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringSecurityApplication.class, args);
    }

}

注解@SpringBootApplication
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan(
excludeFilters = {@Filter(
type = FilterType.CUSTOM,
classes = {TypeExcludeFilter.class}
), @Filter(
type = FilterType.CUSTOM,
classes = {AutoConfigurationExcludeFilter.class}
)}
)
public @interface SpringBootApplication {
@AliasFor(
annotation = EnableAutoConfiguration.class
)
Class<?>[] exclude() default {};

@AliasFor(
    annotation = EnableAutoConfiguration.class
)
String[] excludeName() default {};

@AliasFor(
    annotation = ComponentScan.class,
    attribute = "basePackages"
)
String[] scanBasePackages() default {};

@AliasFor(
    annotation = ComponentScan.class,
    attribute = "basePackageClasses"
)
Class<?>[] scanBasePackageClasses() default {};

@AliasFor(
    annotation = ComponentScan.class,
    attribute = "nameGenerator"
)
Class<? extends BeanNameGenerator> nameGenerator() default BeanNameGenerator.class;

@AliasFor(
    annotation = Configuration.class
)
boolean proxyBeanMethods() default true;

}



核心3个注解：
@SpringBootConfiguration     改注解和@Configuration类似，表面这个类是配置类
@EnableAutoConfiguration    springboot实现自动化配置的核心注解
@ComponentScan    默认扫描启动类当前包以及子包

要了解springboot自动配置原理当然我们需要看@EnableAutoConfiguration

在这2.4版本以前
@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 {};

}

3.4.1版本
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@AutoConfigurationPackage
@Import({AutoConfigurationImportSelector.class})
public @interface EnableAutoConfiguration {
String ENABLED_OVERRIDE_PROPERTY = “spring.boot.enableautoconfiguration”;

Class<?>[] exclude() default {};

String[] excludeName() default {};

}

开启自动配置注解我们需要看这个注解做了什么事？
看上面的代码我们可以发现一个关键的@import注解，
低版本：开启导入自动配置选择器：
源码：
@Deprecated
public class EnableAutoConfigurationImportSelector extends AutoConfigurationImportSelector {
    public EnableAutoConfigurationImportSelector() {
    }

    protected boolean isEnabled(AnnotationMetadata metadata) {
        return this.getClass().equals(EnableAutoConfigurationImportSelector.class) ? (Boolean)this.getEnvironment().getProperty("spring.boot.enableautoconfiguration", Boolean.class, true) : true;
    }
}
``

3.4.1版本
public class AutoConfigurationImportSelector implements DeferredImportSelector, BeanClassLoaderAware, ResourceLoaderAware, BeanFactoryAware, EnvironmentAware, Ordered {
    static final int ORDER = 2147483646;
    private static final AutoConfigurationEntry EMPTY_ENTRY = new AutoConfigurationEntry();
    private static final String[] NO_IMPORTS = new String[0];
    private static final Log logger = LogFactory.getLog(AutoConfigurationImportSelector.class);
    private static final String PROPERTY_NAME_AUTOCONFIGURE_EXCLUDE = "spring.autoconfigure.exclude";
    private final Class<?> autoConfigurationAnnotation;
    private ConfigurableListableBeanFactory beanFactory;
    private Environment environment;
    private ClassLoader beanClassLoader;
    private ResourceLoader resourceLoader;
    private volatile ConfigurationClassFilter configurationClassFilter;
    private volatile AutoConfigurationReplacements autoConfigurationReplacements;

    public AutoConfigurationImportSelector() {
        this((Class)null);
    }

    AutoConfigurationImportSelector(Class<?> autoConfigurationAnnotation) {
        this.autoConfigurationAnnotation = autoConfigurationAnnotation != null ? autoConfigurationAnnotation : AutoConfiguration.class;
    }

    public String[] selectImports(AnnotationMetadata annotationMetadata) {
        if (!this.isEnabled(annotationMetadata)) {
            return NO_IMPORTS;
        } else {
            AutoConfigurationEntry autoConfigurationEntry = this.getAutoConfigurationEntry(annotationMetadata);
            return StringUtils.toStringArray(autoConfigurationEntry.getConfigurations());
        }
    }

    public Predicate<String> getExclusionFilter() {
        return this::shouldExclude;
    }

    private boolean shouldExclude(String configurationClassName) {
        return this.getConfigurationClassFilter().filter(Collections.singletonList(configurationClassName)).isEmpty();
    }

    protected AutoConfigurationEntry getAutoConfigurationEntry(AnnotationMetadata annotationMetadata) {
        if (!this.isEnabled(annotationMetadata)) {
            return EMPTY_ENTRY;
        } else {
            AnnotationAttributes attributes = this.getAttributes(annotationMetadata);
            List<String> configurations = this.getCandidateConfigurations(annotationMetadata, attributes);
            configurations = this.removeDuplicates(configurations);
            Set<String> exclusions = this.getExclusions(annotationMetadata, attributes);
            this.checkExcludedClasses(configurations, exclusions);
            configurations.removeAll(exclusions);
            configurations = this.getConfigurationClassFilter().filter(configurations);
            this.fireAutoConfigurationImportEvents(configurations, exclusions);
            return new AutoConfigurationEntry(configurations, exclusions);
        }
    }

    public Class<? extends DeferredImportSelector.Group> getImportGroup() {
        return AutoConfigurationGroup.class;
    }

    protected boolean isEnabled(AnnotationMetadata metadata) {
        return this.getClass() == AutoConfigurationImportSelector.class ? (Boolean)this.getEnvironment().getProperty("spring.boot.enableautoconfiguration", Boolean.class, true) : true;
    }

    protected AnnotationAttributes getAttributes(AnnotationMetadata metadata) {
        String name = this.getAnnotationClass().getName();
        AnnotationAttributes attributes = AnnotationAttributes.fromMap(metadata.getAnnotationAttributes(name, true));
        Assert.notNull(attributes, () -> {
            String var10000 = metadata.getClassName();
            return "No auto-configuration attributes found. Is " + var10000 + " annotated with " + ClassUtils.getShortName(name) + "?";
        });
        return attributes;
    }

    protected Class<?> getAnnotationClass() {
        return EnableAutoConfiguration.class;
    }

    protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) {
        ImportCandidates importCandidates = ImportCandidates.load(this.autoConfigurationAnnotation, this.getBeanClassLoader());
        List<String> configurations = importCandidates.getCandidates();
        Assert.notEmpty(configurations, "No auto configuration classes found in META-INF/spring/" + this.autoConfigurationAnnotation.getName() + ".imports. If you are using a custom packaging, make sure that file is correct.");
        return configurations;
    }

    private void checkExcludedClasses(List<String> configurations, Set<String> exclusions) {
        List<String> invalidExcludes = new ArrayList(exclusions.size());
        Iterator var4 = exclusions.iterator();

        while(var4.hasNext()) {
            String exclusion = (String)var4.next();
            if (ClassUtils.isPresent(exclusion, this.getClass().getClassLoader()) && !configurations.contains(exclusion)) {
                invalidExcludes.add(exclusion);
            }
        }

        if (!invalidExcludes.isEmpty()) {
            this.handleInvalidExcludes(invalidExcludes);
        }

    }

    protected void handleInvalidExcludes(List<String> invalidExcludes) {
        StringBuilder message = new StringBuilder();
        Iterator var3 = invalidExcludes.iterator();

        while(var3.hasNext()) {
            String exclude = (String)var3.next();
            message.append("\t- ").append(exclude).append(String.format("%n"));
        }

        throw new IllegalStateException(String.format("The following classes could not be excluded because they are not auto-configuration classes:%n%s", message));
    }

    protected Set<String> getExclusions(AnnotationMetadata metadata, AnnotationAttributes attributes) {
        Set<String> excluded = new LinkedHashSet();
        excluded.addAll(this.asList(attributes, "exclude"));
        excluded.addAll(this.asList(attributes, "excludeName"));
        excluded.addAll(this.getExcludeAutoConfigurationsProperty());
        return this.getAutoConfigurationReplacements().replaceAll(excluded);
    }

    protected List<String> getExcludeAutoConfigurationsProperty() {
        Environment environment = this.getEnvironment();
        if (environment == null) {
            return Collections.emptyList();
        } else if (environment instanceof ConfigurableEnvironment) {
            Binder binder = Binder.get(environment);
            return (List)binder.bind("spring.autoconfigure.exclude", String[].class).map(Arrays::asList).orElse(Collections.emptyList());
        } else {
            String[] excludes = (String[])environment.getProperty("spring.autoconfigure.exclude", String[].class);
            return excludes != null ? Arrays.asList(excludes) : Collections.emptyList();
        }
    }

    protected List<AutoConfigurationImportFilter> getAutoConfigurationImportFilters() {
        return SpringFactoriesLoader.loadFactories(AutoConfigurationImportFilter.class, this.beanClassLoader);
    }

    private ConfigurationClassFilter getConfigurationClassFilter() {
        ConfigurationClassFilter configurationClassFilter = this.configurationClassFilter;
        if (configurationClassFilter == null) {
            List<AutoConfigurationImportFilter> filters = this.getAutoConfigurationImportFilters();
            Iterator var3 = filters.iterator();

            while(var3.hasNext()) {
                AutoConfigurationImportFilter filter = (AutoConfigurationImportFilter)var3.next();
                this.invokeAwareMethods(filter);
            }

            configurationClassFilter = new ConfigurationClassFilter(this.beanClassLoader, filters);
            this.configurationClassFilter = configurationClassFilter;
        }

        return configurationClassFilter;
    }

    private AutoConfigurationReplacements getAutoConfigurationReplacements() {
        AutoConfigurationReplacements autoConfigurationReplacements = this.autoConfigurationReplacements;
        if (autoConfigurationReplacements == null) {
            autoConfigurationReplacements = AutoConfigurationReplacements.load(this.autoConfigurationAnnotation, this.beanClassLoader);
            this.autoConfigurationReplacements = autoConfigurationReplacements;
        }

        return autoConfigurationReplacements;
    }

    protected final <T> List<T> removeDuplicates(List<T> list) {
        return new ArrayList(new LinkedHashSet(list));
    }

    protected final List<String> asList(AnnotationAttributes attributes, String name) {
        String[] value = attributes.getStringArray(name);
        return Arrays.asList(value);
    }

    private void fireAutoConfigurationImportEvents(List<String> configurations, Set<String> exclusions) {
        List<AutoConfigurationImportListener> listeners = this.getAutoConfigurationImportListeners();
        if (!listeners.isEmpty()) {
            AutoConfigurationImportEvent event = new AutoConfigurationImportEvent(this, configurations, exclusions);
            Iterator var5 = listeners.iterator();

            while(var5.hasNext()) {
                AutoConfigurationImportListener listener = (AutoConfigurationImportListener)var5.next();
                this.invokeAwareMethods(listener);
                listener.onAutoConfigurationImportEvent(event);
            }
        }

    }

    protected List<AutoConfigurationImportListener> getAutoConfigurationImportListeners() {
        return SpringFactoriesLoader.loadFactories(AutoConfigurationImportListener.class, this.beanClassLoader);
    }

    private void invokeAwareMethods(Object instance) {
        if (instance instanceof Aware) {
            if (instance instanceof BeanClassLoaderAware) {
                BeanClassLoaderAware beanClassLoaderAwareInstance = (BeanClassLoaderAware)instance;
                beanClassLoaderAwareInstance.setBeanClassLoader(this.beanClassLoader);
            }

            if (instance instanceof BeanFactoryAware) {
                BeanFactoryAware beanFactoryAwareInstance = (BeanFactoryAware)instance;
                beanFactoryAwareInstance.setBeanFactory(this.beanFactory);
            }

            if (instance instanceof EnvironmentAware) {
                EnvironmentAware environmentAwareInstance = (EnvironmentAware)instance;
                environmentAwareInstance.setEnvironment(this.environment);
            }

            if (instance instanceof ResourceLoaderAware) {
                ResourceLoaderAware resourceLoaderAwareInstance = (ResourceLoaderAware)instance;
                resourceLoaderAwareInstance.setResourceLoader(this.resourceLoader);
            }
        }

    }

    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        Assert.isInstanceOf(ConfigurableListableBeanFactory.class, beanFactory);
        this.beanFactory = (ConfigurableListableBeanFactory)beanFactory;
    }

    protected final ConfigurableListableBeanFactory getBeanFactory() {
        return this.beanFactory;
    }

    public void setBeanClassLoader(ClassLoader classLoader) {
        this.beanClassLoader = classLoader;
    }

    protected ClassLoader getBeanClassLoader() {
        return this.beanClassLoader;
    }

    public void setEnvironment(Environment environment) {
        this.environment = environment;
    }

    protected final Environment getEnvironment() {
        return this.environment;
    }

    public void setResourceLoader(ResourceLoader resourceLoader) {
        this.resourceLoader = resourceLoader;
    }

    protected final ResourceLoader getResourceLoader() {
        return this.resourceLoader;
    }

    public int getOrder() {
        return 2147483646;
    }

    protected static class AutoConfigurationEntry {
        private final List<String> configurations;
        private final Set<String> exclusions;

        private AutoConfigurationEntry() {
            this.configurations = Collections.emptyList();
            this.exclusions = Collections.emptySet();
        }

        AutoConfigurationEntry(Collection<String> configurations, Collection<String> exclusions) {
            this.configurations = new ArrayList(configurations);
            this.exclusions = new HashSet(exclusions);
        }

        public List<String> getConfigurations() {
            return this.configurations;
        }

        public Set<String> getExclusions() {
            return this.exclusions;
        }
    }

    private static class ConfigurationClassFilter {
        private final AutoConfigurationMetadata autoConfigurationMetadata;
        private final List<AutoConfigurationImportFilter> filters;

        ConfigurationClassFilter(ClassLoader classLoader, List<AutoConfigurationImportFilter> filters) {
            this.autoConfigurationMetadata = AutoConfigurationMetadataLoader.loadMetadata(classLoader);
            this.filters = filters;
        }

        List<String> filter(List<String> configurations) {
            long startTime = System.nanoTime();
            String[] candidates = StringUtils.toStringArray(configurations);
            boolean skipped = false;
            Iterator var6 = this.filters.iterator();

            int i;
            while(var6.hasNext()) {
                AutoConfigurationImportFilter filter = (AutoConfigurationImportFilter)var6.next();
                boolean[] match = filter.match(candidates, this.autoConfigurationMetadata);

                for(i = 0; i < match.length; ++i) {
                    if (!match[i]) {
                        candidates[i] = null;
                        skipped = true;
                    }
                }
            }

            if (!skipped) {
                return configurations;
            } else {
                List<String> result = new ArrayList(candidates.length);
                String[] var12 = candidates;
                int var14 = candidates.length;

                for(i = 0; i < var14; ++i) {
                    String candidate = var12[i];
                    if (candidate != null) {
                        result.add(candidate);
                    }
                }

                if (AutoConfigurationImportSelector.logger.isTraceEnabled()) {
                    int numberFiltered = configurations.size() - result.size();
                    AutoConfigurationImportSelector.logger.trace("Filtered " + numberFiltered + " auto configuration class in " + TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startTime) + " ms");
                }

                return result;
            }
        }
    }

    private static final class AutoConfigurationGroup implements DeferredImportSelector.Group, BeanClassLoaderAware, BeanFactoryAware, ResourceLoaderAware {
        private final Map<String, AnnotationMetadata> entries = new LinkedHashMap();
        private final List<AutoConfigurationEntry> autoConfigurationEntries = new ArrayList();
        private ClassLoader beanClassLoader;
        private BeanFactory beanFactory;
        private ResourceLoader resourceLoader;
        private AutoConfigurationMetadata autoConfigurationMetadata;
        private AutoConfigurationReplacements autoConfigurationReplacements;

        private AutoConfigurationGroup() {
        }

        public void setBeanClassLoader(ClassLoader classLoader) {
            this.beanClassLoader = classLoader;
        }

        public void setBeanFactory(BeanFactory beanFactory) {
            this.beanFactory = beanFactory;
        }

        public void setResourceLoader(ResourceLoader resourceLoader) {
            this.resourceLoader = resourceLoader;
        }

        public void process(AnnotationMetadata annotationMetadata, DeferredImportSelector deferredImportSelector) {
            Assert.state(deferredImportSelector instanceof AutoConfigurationImportSelector, () -> {
                return String.format("Only %s implementations are supported, got %s", AutoConfigurationImportSelector.class.getSimpleName(), deferredImportSelector.getClass().getName());
            });
            AutoConfigurationImportSelector autoConfigurationImportSelector = (AutoConfigurationImportSelector)deferredImportSelector;
            AutoConfigurationReplacements autoConfigurationReplacements = autoConfigurationImportSelector.getAutoConfigurationReplacements();
            Assert.state(this.autoConfigurationReplacements == null || this.autoConfigurationReplacements.equals(autoConfigurationReplacements), "Auto-configuration replacements must be the same for each call to process");
            this.autoConfigurationReplacements = autoConfigurationReplacements;
            AutoConfigurationEntry autoConfigurationEntry = autoConfigurationImportSelector.getAutoConfigurationEntry(annotationMetadata);
            this.autoConfigurationEntries.add(autoConfigurationEntry);
            Iterator var6 = autoConfigurationEntry.getConfigurations().iterator();

            while(var6.hasNext()) {
                String importClassName = (String)var6.next();
                this.entries.putIfAbsent(importClassName, annotationMetadata);
            }

        }

        public Iterable<DeferredImportSelector.Group.Entry> selectImports() {
            if (this.autoConfigurationEntries.isEmpty()) {
                return Collections.emptyList();
            } else {
                Set<String> allExclusions = (Set)this.autoConfigurationEntries.stream().map(AutoConfigurationEntry::getExclusions).flatMap(Collection::stream).collect(Collectors.toSet());
                Set<String> processedConfigurations = (Set)this.autoConfigurationEntries.stream().map(AutoConfigurationEntry::getConfigurations).flatMap(Collection::stream).collect(Collectors.toCollection(LinkedHashSet::new));
                processedConfigurations.removeAll(allExclusions);
                return this.sortAutoConfigurations(processedConfigurations, this.getAutoConfigurationMetadata()).stream().map((importClassName) -> {
                    return new DeferredImportSelector.Group.Entry((AnnotationMetadata)this.entries.get(importClassName), importClassName);
                }).toList();
            }
        }

        private AutoConfigurationMetadata getAutoConfigurationMetadata() {
            if (this.autoConfigurationMetadata == null) {
                this.autoConfigurationMetadata = AutoConfigurationMetadataLoader.loadMetadata(this.beanClassLoader);
            }

            return this.autoConfigurationMetadata;
        }

        private List<String> sortAutoConfigurations(Set<String> configurations, AutoConfigurationMetadata autoConfigurationMetadata) {
            MetadataReaderFactory var10002 = this.getMetadataReaderFactory();
            AutoConfigurationReplacements var10004 = this.autoConfigurationReplacements;
            Objects.requireNonNull(var10004);
            return (new AutoConfigurationSorter(var10002, autoConfigurationMetadata, var10004::replace)).getInPriorityOrder(configurations);
        }

        private MetadataReaderFactory getMetadataReaderFactory() {
            try {
                return (MetadataReaderFactory)this.beanFactory.getBean("org.springframework.boot.autoconfigure.internalCachingMetadataReaderFactory", MetadataReaderFactory.class);
            } catch (NoSuchBeanDefinitionException var2) {
                return new CachingMetadataReaderFactory(this.resourceLoader);
            }
        }
    }
}

在这里插入图片描述

对于spring.factories文件
3.4.1版本
# Auto Configuration Import Filters
org.springframework.boot.autoconfigure.AutoConfigurationImportFilter=\
org.springframework.boot.autoconfigure.condition.OnBeanCondition,\
org.springframework.boot.autoconfigure.condition.OnClassCondition,\
org.springframework.boot.autoconfigure.condition.OnWebApplicationCondition

1.5.2版本
# Auto Configuration Import Filters
org.springframework.boot.autoconfigure.AutoConfigurationImportFilter=\
org.springframework.boot.autoconfigure.condition.OnClassCondition

3.4.1版本可以看到，实现方式发生了变化，引入了配置类过滤器ConfigurationClassFilter来完成bean自动配置的加载
在这里插入图片描述
调用getAutoConfigurationEntry来获取要自动配置的类放入AutoConfigurationEntry对象，这个对象包含2个集合，一个是要自动配置的集合，一个是排除自动配置的集合

spring会跟进这两个集合完成自动配置

低版本的只需要读取spring.factories文件，获取自动配置类进行自动加载bean

spring.factories文件自动配置信息

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,\
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.WebServicesAutoConfiguration

总结：
1.通过@SpringBootConfiguration 引入了@EnableAutoConfiguration(负责启动自动配置功能)
2.@EnableAutoConfiguration引入了@Import
3.Spring容器启动时:加载loc容器时会解析@Import 注解
4.@lmport导入了一个deferredlmportSelector，它会使SpringBoot的自动配置类的顺序在最后，这样方便我们扩展和覆盖?
5.然后读取所有的/META-INF/spring.factories文件(SPI)
6.过滤出所有AutoConfigurtionClass类型的类
7.最后通过@Condition排除无效的自动配置类