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From Knut Anders Hatlen <Knut.Hat...@Sun.COM>
Subject Re: NPE when connecting to database with securityMechanism=8
Date Thu, 23 Aug 2007 14:23:26 GMT
Alan Burlison <Alan.Burlison@Sun.COM> writes:

> Alan Burlison wrote:
>
>>> The network server actually uses the embedded driver to perform database
>>> operations, so any application running in the same JVM as the server
>>> could have access to the database directly through the embedded
>>> driver. In your setup, I think it would make sense to use Derby this
>>> way. The servlets could access the database without doing any network
>>> I/O, and thereby improving the performance, whereas the external scripts
>>> could use the network client driver and don't involve Tomcat. Derby's
>>> manuals call this configuration an "Embedded Server" (see
>>> http://db.apache.org/derby/docs/10.3/adminguide/cadminov17524.html).
>>
>> I knew it worked, but I didn't know if it was correct to use the
>> embedded driver in that situation.  After following the link you
>> sent I found the following in:
>>
>> http://db.apache.org/derby/docs/10.3/adminguide/radminembeddedserverex.html
>>
>> "The program that starts the Network Server can access the database
>> by using either the embedded driver or the Network Client driver."
>
> One other question: If I am attaching to a derby instance that is
> running inside the same JVM, should I be using the client driver or
> the embedded driver?  From observation the client driver works with
> both "jdbc:derby://locahost/mydb" and "jdbc:derby:mydb", but should I
> be using the client driver only for "jdbc:derby://locahost/mydb" and
> the embedded driver for "jdbc:derby:mydb"?

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.

-- 
Knut Anders

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