Perform failure analysis of PersistenceException caused by a FileNotFoundException

[wilkinsona]

#6635 contains an example of the failure:

Caused by: javax.persistence.PersistenceException: Unable to resolve persistence unit root URL
    at org.springframework.orm.jpa.persistenceunit.DefaultPersistenceUnitManager.determineDefaultPersistenceUnitRootUrl(DefaultPersistenceUnitManager.java:603) ~[spring-orm-4.3.1.RELEASE.jar!/:4.3.1.RELEASE]
    at org.springframework.orm.jpa.persistenceunit.DefaultPersistenceUnitManager.preparePersistenceUnitInfos(DefaultPersistenceUnitManager.java:443) ~[spring-orm-4.3.1.RELEASE.jar!/:4.3.1.RELEASE]
    at org.springframework.orm.jpa.persistenceunit.DefaultPersistenceUnitManager.afterPropertiesSet(DefaultPersistenceUnitManager.java:424) ~[spring-orm-4.3.1.RELEASE.jar!/:4.3.1.RELEASE]
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:310) ~[spring-orm-4.3.1.RELEASE.jar!/:4.3.1.RELEASE]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:373) ~[spring-orm-4.3.1.RELEASE.jar!/:4.3.1.RELEASE]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:362) ~[spring-orm-4.3.1.RELEASE.jar!/:4.3.1.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1637) ~[spring-beans-4.3.1.RELEASE.jar!/:4.3.1.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1574) ~[spring-beans-4.3.1.RELEASE.jar!/:4.3.1.RELEASE]
    ... 24 common frames omitted
Caused by: java.io.FileNotFoundException: class path resource [] cannot be resolved to URL because it does not exist
    at org.springframework.core.io.ClassPathResource.getURL(ClassPathResource.java:187) ~[spring-core-4.3.1.RELEASE.jar!/:4.3.1.RELEASE]
    at org.springframework.orm.jpa.persistenceunit.DefaultPersistenceUnitManager.determineDefaultPersistenceUnitRootUrl(DefaultPersistenceUnitManager.java:600) ~[spring-orm-4.3.1.RELEASE.jar!/:4.3.1.RELEASE]
    ... 31 common frames omitted

It happens when JPA is auto-configured but the persistence context is empty. That could be because there are no entities or because scanning is misconfigured.

[wilkinsona]

This may not be necessary depending on the outcome of #6635

[mbhave]

@wilkinsona what outcome of #6635 would make this unnecessary?

[wilkinsona]

An outcome where we manage to provide a default persistence root URL which is what I think #6635 has largely achieved. There's still a case where it doesn't quite work. See https://jira.spring.io/browse/SPR-17297 and #14279. I'm not sure what benefit a failure analyser would be for that specific scenario and that's the only one left as far as I know. I think we can close this one.