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From Knut Anders Hatlen <Knut.Hat...@Sun.COM>
Subject Re: NPE when connecting to database with securityMechanism=8
Date Sat, 25 Aug 2007 06:55:50 GMT
Alan Burlison <Alan.Burlison@Sun.COM> writes:

> Knut Anders Hatlen wrote:
>
>> You shouldn't load the client driver unless your application uses
>> jdbc:derby://localhost/mydb. The reason why the client driver seems to
>> work in your case, is that the server already has loaded the embedded
>> driver. So the code that runs inside the same JVM as the server should
>> use jdbc:derby:mydb and not load the client driver, whereas the external
>> scripts should load the client driver and use
>> jdbc:derby://localhost/mydb.
>
> Unfortunately it's not that simple.  If you use the embedded driver
> with STRONG_PASSWORD_SUBSTITUTE_SECURITY & securityMechanism=8, you
> get a NPE is you open, close and then reopen the database - which is
> necessary if you want to be sure that the static database properties
> you set are used.

OK, I think I see the problem now. It seems like if you connect to a
database which has derby.connection.requireAuthentication=true using the
embedded driver, Derby throws a NPE if the securityMechanism connection
attribute is specified. Specifying the securityMechanism attribute for
an embedded connection doesn't really make any sense, I think, since it
says how to send passwords over a network connection, and the embedded
driver doesn't use the network.

This means you will have to connect without securityMechanism when you
connect from within Tomcat (with the embedded driver), and with
securityMechanism when you connect from the external scripts (with the
client driver).

Of course, you should have got an exception with a message explaining
the problem, not a NPE.

HTH,
-- 
Knut Anders

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