1. 问题原因Spring Data MongoDB 3.x不在提供自动创建索引

> 2021-03-18 15:29:14 |WARN  |restartedMain |JustOnceLogger.java:72 |org.springframework.data.mongodb.core.index.MongoPersistentEntityIndexCreator |Automatic index creation will be disabled by default as of Spring Data MongoDB 3.x.
	Please use 'MongoMappingContext#setAutoIndexCreation(boolean)' or override 'MongoConfigurationSupport#autoIndexCreation()' to be explicit.
	However, we recommend setting up indices manually in an application ready block. You may use index derivation there as well.

	> -----------------------------------------------------------------------------------------
	> @EventListener(ApplicationReadyEvent.class)
	> public void initIndicesAfterStartup() {
	>
	>     IndexOperations indexOps = mongoTemplate.indexOps(DomainType.class);
	>
	>     IndexResolver resolver = new MongoPersistentEntityIndexResolver(mongoMappingContext);
	>     resolver.resolveIndexFor(DomainType.class).forEach(indexOps::ensureIndex);
	> }
	> -----------------------------------------------------------------------------------------

2.解决办法：自动创建改为false

spring:
  data:
    mongodb:
      auto-index-creation: false