Having "APPLICATION FAILED TO START" error on Spring Boot startup - mongodb

Question

I'm developing an API on Spring Boot using Vault and Mongo, but it refuses to start.
2022-09-07 13:58:56.510 WARN 23885 --- [ main] s.c.a.AnnotationConfigApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'org.springframework.cloud.vault.config.VaultReactiveBootstrapConfiguration': Unsatisfied dependency expressed through constructor parameter 0; nested exception is org.springframework.boot.context.properties.ConfigurationPropertiesBindException: Error creating bean with name 'spring.cloud.vault-org.springframework.cloud.vault.config.VaultProperties': Could not bind properties to 'VaultProperties' : prefix=spring.cloud.vault, ignoreInvalidFields=false, ignoreUnknownFields=true; nested exception is javax.validation.NoProviderFoundException: Unable to create a Configuration, because no Jakarta Bean Validation provider could be found. Add a provider like Hibernate Validator (RI) to your classpath.
2022-09-07 13:58:56.513 INFO 23885 --- [ main] ConditionEvaluationReportLoggingListener :
Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2022-09-07 13:58:56.521 ERROR 23885 --- [ main] o.s.b.d.LoggingFailureAnalysisReporter :
***************************
APPLICATION FAILED TO START
***************************
Description:
The Bean Validation API is on the classpath but no implementation could be found
Action:
Add an implementation, such as Hibernate Validator, to the classpath
EDIT: I think the problem is that Spring Boot tries to use javax and jakarta at the same time according to this part of the error:
nested exception is javax.validation.NoProviderFoundException: Unable to create a Configuration, because no Jakarta Bean Validation provider could be found.. Is this a normal behavior?

Answer 1

Consider to bypass the problem: try to add compile 'de.flapdoodle.embed:de.flapdoodle.embed.mongo' to your build.gradle, and #Bean public MongoClient embeddedMongoClient() to return a dummy Mongo client during the Init phase.
The real mongo Url could be fetched (and used) from the Vault later, during run time, once required, via a customized extends of spring-data-mongodb's MongoDbFactory.

Answer 2

Adding hibernate-validator 6 and spring-boot-starter-validation solved the problem.
Thing to know: hibernate-validator < 7 uses Javax, hibernate-validator => 7 uses Jakarta.
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-validation</artifactId>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-validator</artifactId>
<version>6.2.4.Final</version>
</dependency>