What we need to provide is not a default *Configuration*, but a default *AppConfigurationEntry* for the JGSS named entries.
The reason is that users may still have JAAS configuration files as ~/java.login.config etc etc for their JAAS programs. However, when they write JGSS programs, they may not realize that entries like com.sun.security.jgss.krb5.* are needed *inside* the file, I believe this is the case we want to give them a default setting.
So, I'd like to --
1. In Configuration.getConfiguration
a. Throw Exception if bad file syntax, or files specified by don't exist (for java.security.auth.login.config and/or login.config.url.n)
b. return empty if not specified at all
c. return something if there's such a valid file (may still be empty ;) )
2. In LoginConfigImpl.java
1) find the entry and return the content
2) if entry not found, return default