spring.factories
在Spring中有一种非常解耦的扩展机制：Spring Factories。这种扩展机制实际上是仿照Java中的SPI扩展机制来实现的。

Java SPI约定

Java SPI机制SPI的全名为Service Provider Interface.这个是针对厂商或者插件的。在java.util.ServiceLoader的文档里有比较详细的介绍。我们系统里抽象的各个模块，往往有很多不同的实现方案，比如日志模块的方案，xml解析模块、jdbc模块的方案等。面向的对象的设计里，我们一般推荐模块之间基于接口编程，模块之间不对实现类进行硬编码。一旦代码里涉及具体的实现类，就违反了可拔插的原则，如果需要替换一种实现，就需要修改代码。为了实现在模块装配的时候能不在程序里动态指明，这就需要一种服务发现机制。 java spi就是提供这样的一个机制：为某个接口寻找服务实现的机制。有点类似IOC的思想，就是将装配的控制权移到程序之外，在模块化设计中这个机制尤其重要。

java spi的具体约定为:当服务的提供者，提供了服务接口的一种实现之后，在jar包的META-INF/services/目录里同时创建一个以服务接口命名的文件。该文件里就是实现该服务接口的具体实现类。而当外部程序装配这个模块的时候，就能通过该jar包META-INF/services/里的配置文件找到具体的实现类名，并装载实例化，完成模块的注入。基于这样一个约定就能很好的找到服务接口的实现类，而不需要再代码里制定。jdk提供服务实现查找的一个工具类：java.util.ServiceLoader

Spring中的SPI机制

在Spring中也有一种类似与Java SPI的加载机制。它在META-INF/spring.factories文件中配置接口的实现类名称，然后在程序中读取这些配置文件并实例化。这种自定义的SPI机制是Spring Boot Starter实现的基础。

Spring Factories实现原理

spring-core包里定义了SpringFactoriesLoader类，这个类实现了检索META-INF/spring.factories（org.springframework.core.io.support.SpringFactoriesLoader#FACTORIES_RESOURCE_LOCATION）文件，并获取指定接口的配置的功能。在这个类中定义了两个对外的方法：

loadFactories：根据接口类获取其实现类的实例，这个方法返回的是对象列表。

loadFactoryNames：根据接口获取其接口类的名称，这个方法返回的是类名的列表。

上面的两个方法的关键都是从指定的ClassLoader中获取spring.factories文件，并解析得到类名列表，具体代码如下


/*** General purpose factory loading mechanism for internal use within the framework.** <p>{@code SpringFactoriesLoader} {@linkplain #loadFactories loads} and instantiates* factories of a given type from {@value #FACTORIES_RESOURCE_LOCATION} files which* may be present in multiple JAR files in the classpath. The {@code spring.factories}* file must be in {@link Properties} format, where the key is the fully qualified* name of the interface or abstract class, and the value is a comma-separated list of* implementation class names. For example:** <pre class="code">example.MyService=example.MyServiceImpl1,example.MyServiceImpl2</pre>** where {@code example.MyService} is the name of the interface, and {@code MyServiceImpl1}* and {@code MyServiceImpl2} are two implementations.** @author Arjen Poutsma* @author Juergen Hoeller* @author Sam Brannen* @since 3.2*/
public final class SpringFactoriesLoader {/*** The location to look for factories.* <p>Can be present in multiple JAR files.*/public static final String FACTORIES_RESOURCE_LOCATION = "META-INF/spring.factories";private static final Log logger = LogFactory.getLog(SpringFactoriesLoader.class);private static final Map<ClassLoader, MultiValueMap<String, String>> cache = new ConcurrentReferenceHashMap<>();private SpringFactoriesLoader() {}/*** Load and instantiate the factory implementations of the given type from* {@value #FACTORIES_RESOURCE_LOCATION}, using the given class loader.* <p>The returned factories are sorted through {@link AnnotationAwareOrderComparator}.* <p>If a custom instantiation strategy is required, use {@link #loadFactoryNames}* to obtain all registered factory names.* @param factoryClass the interface or abstract class representing the factory* @param classLoader the ClassLoader to use for loading (can be {@code null} to use the default)* @throws IllegalArgumentException if any factory implementation class cannot* be loaded or if an error occurs while instantiating any factory* @see #loadFactoryNames*/public static <T> List<T> loadFactories(Class<T> factoryClass, @Nullable ClassLoader classLoader) {Assert.notNull(factoryClass, "'factoryClass' must not be null");ClassLoader classLoaderToUse = classLoader;if (classLoaderToUse == null) {classLoaderToUse = SpringFactoriesLoader.class.getClassLoader();}List<String> factoryNames = loadFactoryNames(factoryClass, classLoaderToUse);if (logger.isTraceEnabled()) {logger.trace("Loaded [" + factoryClass.getName() + "] names: " + factoryNames);}List<T> result = new ArrayList<>(factoryNames.size());for (String factoryName : factoryNames) {result.add(instantiateFactory(factoryName, factoryClass, classLoaderToUse));}AnnotationAwareOrderComparator.sort(result);return result;}/*** Load the fully qualified class names of factory implementations of the* given type from {@value #FACTORIES_RESOURCE_LOCATION}, using the given* class loader.* @param factoryClass the interface or abstract class representing the factory* @param classLoader the ClassLoader to use for loading resources; can be* {@code null} to use the default* @throws IllegalArgumentException if an error occurs while loading factory names* @see #loadFactories*/public static List<String> loadFactoryNames(Class<?> factoryClass, @Nullable ClassLoader classLoader) {String factoryClassName = factoryClass.getName();return loadSpringFactories(classLoader).getOrDefault(factoryClassName, Collections.emptyList());}private static Map<String, List<String>> loadSpringFactories(@Nullable ClassLoader classLoader) {MultiValueMap<String, String> result = cache.get(classLoader);if (result != null) {return result;}try {Enumeration<URL> urls = (classLoader != null ?classLoader.getResources(FACTORIES_RESOURCE_LOCATION) :ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION));result = new LinkedMultiValueMap<>();while (urls.hasMoreElements()) {URL url = urls.nextElement();UrlResource resource = new UrlResource(url);Properties properties = PropertiesLoaderUtils.loadProperties(resource);for (Map.Entry<?, ?> entry : properties.entrySet()) {String factoryClassName = ((String) entry.getKey()).trim();for (String factoryName : StringUtils.commaDelimitedListToStringArray((String) entry.getValue())) {result.add(factoryClassName, factoryName.trim());}}}cache.put(classLoader, result);return result;}catch (IOException ex) {throw new IllegalArgumentException("Unable to load factories from location [" +FACTORIES_RESOURCE_LOCATION + "]", ex);}}@SuppressWarnings("unchecked")private static <T> T instantiateFactory(String instanceClassName, Class<T> factoryClass, ClassLoader classLoader) {try {Class<?> instanceClass = ClassUtils.forName(instanceClassName, classLoader);if (!factoryClass.isAssignableFrom(instanceClass)) {throw new IllegalArgumentException("Class [" + instanceClassName + "] is not assignable to [" + factoryClass.getName() + "]");}return (T) ReflectionUtils.accessibleConstructor(instanceClass).newInstance();}catch (Throwable ex) {throw new IllegalArgumentException("Unable to instantiate factory class: " + factoryClass.getName(), ex);}}}

加载factories文件

从代码中我们可以知道，在这个方法中会遍历整个ClassLoader中所有jar包下的spring.factories文件。也就是说我们可以在自己的jar中配置spring.factories文件，不会影响到其它地方的配置，也不会被别人的配置覆盖。

spring.factories的是通过Properties解析得到的，所以我们在写文件中的内容都是安装下面这种方式配置的：

com.xxx.interface=com.xxx.ClassName

如果一个接口希望配置多个实现类，可以使用’,'进行分割。

在Spring Boot的很多包中都能够找到spring.factories文件

在日常工作中，我们可能需要实现一些SDK或者Spring Boot Starter给被人使用，这个使用我们就可以使用Factories机制。Factories机制可以让SDK或者Starter的使用只需要很少或者不需要进行配置，只需要在服务中引入我们的jar包。

如何使用指定构造方法实例化？

对于loadFactories方法而言，在获取类列表的基础上，还有进行实例化的过程，它只支持没有参数的构造函数。但是我们可以通过loadFactoryNames方法获取类名，然后自己通过获取指定的构造方法进行实例化，SpringBoot中就使用了这样的技巧。

 private <T> Collection<? extends T> getSpringFactoriesInstances(Class<T> type) {return getSpringFactoriesInstances(type, new Class<?>[] {});}private <T> Collection<? extends T> getSpringFactoriesInstances(Class<T> type,Class<?>[] parameterTypes, Object... args) {ClassLoader classLoader = Thread.currentThread().getContextClassLoader();// Use names and ensure unique to protect against duplicatesSet<String> names = new LinkedHashSet<String>(SpringFactoriesLoader.loadFactoryNames(type, classLoader));List<T> instances = createSpringFactoriesInstances(type, parameterTypes,classLoader, args, names);AnnotationAwareOrderComparator.sort(instances);return instances;}@SuppressWarnings("unchecked")private <T> List<T> createSpringFactoriesInstances(Class<T> type,Class<?>[] parameterTypes, ClassLoader classLoader, Object[] args,Set<String> names) {List<T> instances = new ArrayList<T>(names.size());for (String name : names) {try {Class<?> instanceClass = ClassUtils.forName(name, classLoader);Assert.isAssignable(type, instanceClass);Constructor<?> constructor = instanceClass.getDeclaredConstructor(parameterTypes);T instance = (T) BeanUtils.instantiateClass(constructor, args);instances.add(instance);}catch (Throwable ex) {throw new IllegalArgumentException("Cannot instantiate " + type + " : " + name, ex);}}return instances;}

然后实例化 ApplicationContextInitializer、ApplicationListener、SpringApplicationRunListener 都使用了以上方法。

Spring Boot Factories

Spring boot中默认使用了很多factories机制，主要包含：

ApplicationContextInitializer：用于在spring容器刷新之前初始化Spring ConfigurableApplicationContext的回调接口。
ApplicationListener：用于处理容器初始化各个阶段的事件。
AutoConfigurationImportListener：导入配置类的时候，获取类的详细信息（Listener that can be registered with spring.factories to receive details of imported auto-configurations.）。
AutoConfigurationImportFilter：用于按条件过滤导入的配置类（Filter that can be registered in spring.factories to limit the auto-configuration classes considered. This interface is designed to allow fast removal of auto-configuration classes before their bytecode is even read.）
EnableAutoConfiguration：指定自动加载的配置类列表（Enable auto-configuration of the Spring Application Context, attempting to guess and configure beans that you are likely to need. Auto-configuration classes are usually applied based on your classpath and what beans you have defined. For example, if you have tomcat-embedded.jar on your classpath you are likely to want a TomcatServletWebServerFactory (unless you have defined your own ServletWebServerFactory bean).
FailureAnalyzer：在启动时拦截异常并将其转换为易读的消息，并将其包含在FailureAnalysis中。 Spring Boot为应用程序上下文相关异常、JSR-303验证等提供了此类分析器（A FailureAnalyzer is used to analyze a failure and provide diagnostic information that can be displayed to the user.）
TemplateAvailabilityProvider：模版引擎配置。（Collection of TemplateAvailabilityProvider beans that can be used to check which (if any) templating engine supports a given view. Caches responses unless the spring.template.provider.cache property is set to false.）

从SpringBoot的使用方式中我们知道，spring.factories中的key不一定必须是接口，甚至都可以是注解。比如org.springframework.boot.autoconfigure.EnableAutoConfiguration。因为没有这方面要求，spring.factories机制只提供获取某个key有哪些值，并不要求必须是接口和实现类的关系。

spring boot 自带factories文件示例

Initializers

org.springframework.context.ApplicationContextInitializer=
org.springframework.boot.autoconfigure.SharedMetadataReaderFactoryContextInitializer,
org.springframework.boot.autoconfigure.logging.ConditionEvaluationReportLoggingListener

Application Listeners

org.springframework.context.ApplicationListener=
org.springframework.boot.autoconfigure.BackgroundPreinitializer

Auto Configuration Import Listeners

org.springframework.boot.autoconfigure.AutoConfigurationImportListener=
org.springframework.boot.autoconfigure.condition.ConditionEvaluationReportAutoConfigurationImportListener

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

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.context.ConfigurationPropertiesAutoConfiguration,
org.springframework.boot.autoconfigure.context.LifecycleAutoConfiguration,
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.ElasticsearchDataAutoConfiguration,
org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchRepositoriesAutoConfiguration,
org.springframework.boot.autoconfigure.data.elasticsearch.ReactiveElasticsearchRepositoriesAutoConfiguration,
org.springframework.boot.autoconfigure.data.elasticsearch.ReactiveElasticsearchRestClientAutoConfiguration,
org.springframework.boot.autoconfigure.data.jdbc.JdbcRepositoriesAutoConfiguration,
org.springframework.boot.autoconfigure.data.jpa.JpaRepositoriesAutoConfiguration,
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.r2dbc.R2dbcDataAutoConfiguration,
org.springframework.boot.autoconfigure.data.r2dbc.R2dbcRepositoriesAutoConfiguration,
org.springframework.boot.autoconfigure.data.r2dbc.R2dbcTransactionManagerAutoConfiguration,
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.ElasticsearchRestClientAutoConfiguration,
org.springframework.boot.autoconfigure.flyway.FlywayAutoConfiguration,
org.springframework.boot.autoconfigure.freemarker.FreeMarkerAutoConfiguration,
org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAutoConfiguration,
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.jersey.JerseyAutoConfiguration,
org.springframework.boot.autoconfigure.jooq.JooqAutoConfiguration,
org.springframework.boot.autoconfigure.jsonb.JsonbAutoConfiguration,
org.springframework.boot.autoconfigure.kafka.KafkaAutoConfiguration,
org.springframework.boot.autoconfigure.availability.ApplicationAvailabilityAutoConfiguration,
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.r2dbc.R2dbcAutoConfiguration,
org.springframework.boot.autoconfigure.rsocket.RSocketMessagingAutoConfiguration,
org.springframework.boot.autoconfigure.rsocket.RSocketRequesterAutoConfiguration,
org.springframework.boot.autoconfigure.rsocket.RSocketServerAutoConfiguration,
org.springframework.boot.autoconfigure.rsocket.RSocketStrategiesAutoConfiguration,
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.security.rsocket.RSocketSecurityAutoConfiguration,
org.springframework.boot.autoconfigure.security.saml2.Saml2RelyingPartyAutoConfiguration,
org.springframework.boot.autoconfigure.sendgrid.SendGridAutoConfiguration,
org.springframework.boot.autoconfigure.session.SessionAutoConfiguration,
org.springframework.boot.autoconfigure.security.oauth2.client.servlet.OAuth2ClientAutoConfiguration,
org.springframework.boot.autoconfigure.security.oauth2.client.reactive.ReactiveOAuth2ClientAutoConfiguration,
org.springframework.boot.autoconfigure.security.oauth2.resource.servlet.OAuth2ResourceServerAutoConfiguration,
org.springframework.boot.autoconfigure.security.oauth2.resource.reactive.ReactiveOAuth2ResourceServerAutoConfiguration,
org.springframework.boot.autoconfigure.solr.SolrAutoConfiguration,
org.springframework.boot.autoconfigure.task.TaskExecutionAutoConfiguration,
org.springframework.boot.autoconfigure.task.TaskSchedulingAutoConfiguration,
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.ClientHttpConnectorAutoConfiguration,
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,
org.springframework.boot.autoconfigure.webservices.client.WebServiceTemplateAutoConfiguration

Failure analyzers

org.springframework.boot.diagnostics.FailureAnalyzer=
org.springframework.boot.autoconfigure.data.redis.RedisUrlSyntaxFailureAnalyzer,
org.springframework.boot.autoconfigure.diagnostics.analyzer.NoSuchBeanDefinitionFailureAnalyzer,
org.springframework.boot.autoconfigure.flyway.FlywayMigrationScriptMissingFailureAnalyzer,
org.springframework.boot.autoconfigure.jdbc.DataSourceBeanCreationFailureAnalyzer,
org.springframework.boot.autoconfigure.jdbc.HikariDriverConfigurationFailureAnalyzer,
org.springframework.boot.autoconfigure.r2dbc.ConnectionFactoryBeanCreationFailureAnalyzer,
org.springframework.boot.autoconfigure.session.NonUniqueSessionRepositoryFailureAnalyzer

Template availability providers

org.springframework.boot.autoconfigure.template.TemplateAvailabilityProvider=
org.springframework.boot.autoconfigure.freemarker.FreeMarkerTemplateAvailabilityProvider,
org.springframework.boot.autoconfigure.mustache.MustacheTemplateAvailabilityProvider,
org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAvailabilityProvider,
org.springframework.boot.autoconfigure.thymeleaf.ThymeleafTemplateAvailabilityProvider,
org.springframework.boot.autoconfigure.web.servlet.JspTemplateAvailabilityProvider

参考文献
https://www.cnblogs.com/itplay/p/9927892.html

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