BatchJobUtils#purgeOwnedRepositoryData(String tagName) throws unexpected exception

[scottkurz]

From: haotian@java.net

When calling BatchJobUtils#purgeOwnedRepositoryData(String tagName), if the datasource is not available or the batch schema not created, both will throw NullPointerException

Expected Results:

1. If the available datasource not available, a meaningful exception should be thrown rather than NullPointerException.

2. If the batch schema not created, then this method should return silently because there is no data to purge.