How to use DBConnectionPool implemented by Singleton Pattern in struts

[Yun Sang Jung <na...@channeli.net>]

Hi.. all

I hope to use DBConnectionPool in struts.
So I made DBActionBase class (extends ActionBase) to use DBConnectionPool with struts
and I have called getDBConnection and freeDBConnection in perform method.
DBConnectionManager is implemented by using Singleton Pattern.

My question is "Is my below code for DBConnectionPool correct?"
Is there no chance for DBConnection to be gced?
If yes, how can I avoid gc?

====================== code begin ======================
import java.sql.*;
import org.apache.struts.action.*;

abstract public class DBActionBase extends ActionBase {
 protected String dbname = "idb";
 DBConnectionManager connMgr = null;

 protected Connection getDBConnection() throws SQLException {
  connMgr = DBConnectionManager.getInstance();
  if (connMgr == null)
   throw new SQLException ("Cannot access DBPoolManager");
  else
   return connMgr.getConnection (dbname);
 }

 protected void freeDBConnection (Connection conn) {
  connMgr.freeConnection (dbname, conn);
 }
}
====================== code end ======================

Regards,
Jung

Re: How to use DBConnectionPool implemented by Singleton Pattern in struts

[Pierre Metras <ge...@sympatico.ca>]

Hi Jung,

I don't know exactly how the class instances are shared between all the servlets in an application (nor the attributes. I'll have to investigate servlets documentation). What I have done and it seems to work is follow struts documentation:

1) I wrote a Startup servlet that creates a single instance of ConnectionManager, and then keep it with
        setAttribute("com.acme.idb.pool", connMgr);

2) From the ActionBase, in the perform call to obtain a reference to the servlet, retrieve the pool with
        connMgr = (ConnectionMgr) servlet.getAttribute("com.acme.idb.pool");

I hope the server is responsible for synchronization on attributes access. I only have to write synchronized method to obtain and release DB connections.

Regards

Pierre Metras
  ----- Original Message ----- 
  From: Yun Sang Jung 
  To: struts-user@jakarta.apache.org 
  Sent: Friday, August 18, 2000 2:55 AM
  Subject: How to use DBConnectionPool implemented by Singleton Pattern in struts


   
  Hi.. all

  I hope to use DBConnectionPool in struts.
  So I made DBActionBase class (extends ActionBase) to use DBConnectionPool with struts
  and I have called getDBConnection and freeDBConnection in perform method.
  DBConnectionManager is implemented by using Singleton Pattern.

  My question is "Is my below code for DBConnectionPool correct?"
  Is there no chance for DBConnection to be gced?
  If yes, how can I avoid gc?

  ====================== code begin ======================
  import java.sql.*;
  import org.apache.struts.action.*;

  abstract public class DBActionBase extends ActionBase {
   protected String dbname = "idb";
   DBConnectionManager connMgr = null;

   protected Connection getDBConnection() throws SQLException {
    connMgr = DBConnectionManager.getInstance();
    if (connMgr == null)
     throw new SQLException ("Cannot access DBPoolManager");
    else
     return connMgr.getConnection (dbname);
   }

   protected void freeDBConnection (Connection conn) {
    connMgr.freeConnection (dbname, conn);
   }
  }
  ====================== code end ======================

  Regards,
  Jung