Call
log.debugf("On call to EntityIdentifierReaderImpl#resolve [for %s], EntityKey was already known; " +
"should only happen on root returns with an optional identifier specified"
);
throws an Exception:
java.util.MissingFormatArgumentException: Format specifier 's'
at java.util.Formatter.format(Formatter.java:2487)
at java.util.Formatter.format(Formatter.java:2423)
at java.lang.String.format(String.java:2797)
at org.jboss.logging.Slf4jLocationAwareLogger.doLogf(Slf4jLocationAwareLogger.java:81)
at org.jboss.logging.Logger.debugf(Logger.java:553)
at org.hibernate.loader.plan.exec.process.internal.EntityReferenceInitializerImpl.resolveEntityKey(EntityReferenceInitializerImpl.java:142)
at org.hibernate.loader.plan.exec.process.spi.AbstractRowReader.resolveEntityKey(AbstractRowReader.java:146)
at org.hibernate.loader.plan.exec.process.spi.AbstractRowReader.readRow(AbstractRowReader.java:95)
at org.hibernate.loader.plan.exec.spi.EntityLoadQueryDetails$EntityLoaderRowReader.readRow(EntityLoadQueryDetails.java:282)
at org.hibernate.loader.plan.exec.process.internal.ResultSetProcessorImpl.extractResults(ResultSetProcessorImpl.java:129)
at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:129)
at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:93)

This happened after I called flush() and clear() on EntityManager in a JUnit-test