The realm documentaion e.g. http://jakarta.apache.org/tomcat/tomcat-5.0-doc/config/realm.html doesn't mention that JDBCRealm (and DataSourceRealm) currently cannot support DIGEST authentication. There is an old bug report, bug#19767, which analysis the problem in detail: some basic functions which are required for the Digest authentication are not implemented. Based on google search several people were affected by the problem. Moreover, there isn't any kind of error message or log entry which could help, this makes the problem more severe.
Care to submit a doc patch?
The user database implementation in Tomcat 5.0.29 doesn't seem to work with DIGEST authentication.
OK, docs clarified. Thanks for your suggestion.