RE: [OFF-TOPIC]Yoav --> RE: Some pretty basic TomcatConnectionPooling Questions????

["Shapira, Yoav" <Yo...@mpi.com>]

Hi,
That's a pretty good solution, yeah.  The "include" you refer to can be
done in several nice OO ways, such as a common parent class or a
singleton utility.

Yoav Shapira
Millennium Research Informatics


>-----Original Message-----
>From: Luke (Terry) Vanderfluit [mailto:luke@chipcity.com.au]
>Sent: Friday, September 10, 2004 11:15 PM
>To: tomcat-user@jakarta.apache.org
>Subject: RE: [OFF-TOPIC]Yoav --> RE: Some pretty basic
>TomcatConnectionPooling Questions????
>
>Hi Yoav and all,
>
>Thanks for your reply,
>
>> But you went a bit too far: the DataSource lookup is potentially
>> expensive.  That you can do in the init() method and keep a reference
to
>> the DataSource, because keeping that reference doesn't use a
connection
>> resource.
>> Then in your servlet methods, get a connection from the DataSource,
use
>> it, and release it.
>> In your servlet destroy method, null out your DataSource reference.
>> So the DataSource lookup is done once, the DataSource reference is
kept
>> as a private non-static member variable of the servlet class, and the
>> Connenctions are used only within methods, they're not class member
>> variables.
>
>So now I have changed my code to:
>1. Declaration of private global variables:
><code>
>   private Context ctx = null;
>   private DataSource ds = null;
>   private Connection conn;
></code>
>
>2. an init() method:
><code>
>// "init" does DataSource lookup
>   public void init(ServletConfig config) throws ServletException {
>      super.init(config);
>      try {
>         ctx = new InitialContext();
>         if(ctx == null) {
>            throw new Exception("No Context");
>         }
>         ds = (DataSource)ctx.lookup("java:comp/env/jdbc/mb");
>      } // end try block
>      catch(Exception e) {
>         e.printStackTrace();
>      }
>   } // end init()
></code>
>
>3. an openConnection() method:
><code>
>   private void openConnection() {
>      try {
>         if(ds != null) {
>            conn = ds.getConnection();
>            if(conn != null) {
>               message = "Got Connection to DB " + conn.toString();
>               }
>            }
>         } // end try block
>      catch(Exception e) {
>         e.printStackTrace();
>         }
>      } //end method openConnection()
></code>
>
>4. a destroy() method that nulls the DataSource:
><code>
>   public void destroy() {
>   ds = null;
>   }
></code>
>
><remarks>
>-the conn.close() is called in the methods that call openConnection().
>-I'm thinking of doing an 'include' for the openConnection method, so I
>don't have the code for the same method sitting in multiple classes.
>Would that be a good idea? (maintainability, yes but in terms of
>overhead?)
></remarks>
>
>Would this be the 'leanest' scenario for a database connection?
>thanks again,
>Luke
>
>--
>========================
>Luke (Terry) Vanderfluit
>Mobile: 0421 276 282
>========================
>
>
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