Re: Help Needed with Connection Pooling for Java Swing Based - Mailing list pgsql-jdbc

Derek:

Are you sure instantiating a Swing component launches a new thread?
Simply instantiating 2 JButtons will launch 2 threads?  I don't think
that is the case.

Derek S wrote:

> Instantiating any Swing component does in fact start a new thread -
> the AWT Event Dispatch thread.  My experience with it has been that
> this thread quite often doesn't terminate the way you might expect
> when the main method ends.  This is a well known issue that Swing and
> AWT programmers simply have to deal with and has absolutely nothing to
> do with JDBC.  Generally speaking, all Swing/AWT based applications
> call System.exit when they are finished doing whatever it is they do
> in order to ensure that the AWT Event Dispatch thread shuts down
> properly.
>
> Barry Lind wrote:
>
>> I just ran your test case and everything seems to be working
>> correctly as far as I can tell.  The program creates one and only one
>> connection to the database.  I don't see multiple connections created
>> as you are reporting.
>>
>> I don't know anything about swing, but it is clear that the code for
>> swing you have below isn't correct.  Because with this swing call the
>> program doesn't exit.  It seems the swing code is starting some other
>> threads that are running and thus the main program doesn't exit until
>> those threads stop running (and I don't know what swing calls are
>> necessary to stop the swing threads from running).
>>
>> So with the swing call in place I have to ctrl-C to stop the app from
>> running, but from the jdbc side of things everything seems to be
>> working correctly.
>>
>> Perhaps I don't understand the problem you are seeing?
>>
>> thanks,
>> --Barry
>>
>>
>> Shanmugasundaram Doraisamy wrote:
>>
>>> Dear group,
>>>
>>> We are having some problems when using JDBC Connection Pool using
>>> Postgrsql Jdbc3PoolingDataSource.
>>>
>>> The Pool behaves fine if there is no Swing Component in the Program.
>>> If there is a swing Component ,then the connection seems to be not
>>> returning to the pool and calling for an additional instance of the
>>> class leeds to the creation of fresh Connection objects ,at times it
>>> even exceeds the maximum number allowed in the pool.
>>> If we go for System.exit(0);(Killing) then only the Connection is
>>> returned .
>>>
>>> But if we comment the swing component line (here in the attached
>>> Program a JOptionPane is Used) then the pool behaves fine.
>>>
>>>
>>> Herewith Iam attaching a Program which is behaving as detailed.
>>>
>>> Any Help is Welcome.
>>>
>>> ##################################################################
>>>
>>>
>>> ##################################################################
>>>
>>> /*
>>>  * ConPool.java
>>>  *
>>>  * Created on 26 March 2003, 11:54
>>>  */
>>>
>>> /**
>>>  *
>>>  * @author  naks from vpsd,Erode
>>>  *   */
>>> import org.postgresql.jdbc3.*;
>>> import java.sql.*;
>>>
>>> public class ConPool {
>>>        Jdbc3PoolingDataSource source = null;
>>>     private Connection conn = null;
>>>        /** Creates a new instance of ConPool */
>>>     public ConPool() {
>>>            }
>>>        /** Setting the Pool which intializes the Pool to 2. */
>>>     public void setPool() {
>>>         // DataSource initialization
>>>         System.out.println("setPool()");
>>>         try {
>>>             System.out.println("setting pool");
>>>             // constructs a pool only when source is not assigned.
>>>             // this will prevent problems if the same pool is set
>>> more than
>>>             // one time
>>>             if (source == null) {
>>>                 source = new Jdbc3PoolingDataSource();
>>>                 // DataSource configuration.
>>>                       source.setServerName("192.168.0.51");
>>>         source.setDatabaseName("kec_test_pool");
>>>         source.setUser("venbro");
>>>         source.setPassword("venbro");
>>>         source.setMaxConnections(2);
>>>                                } else {
>>>                 System.out.println("pool is set");
>>>                 return;
>>>             }
>>>         } catch (Exception loException) {
>>>             // logger.logToFile(loException);
>>>             loException.printStackTrace();
>>>         }
>>>
>>>     } //End of setPool method
>>>           /**
>>>      * Method inserts data to a table "test" which is like
>>>      * create table test (param1 varchar(2),param2 varchar(2)) ;
>>>          */
>>>      public int insertDatas(){
>>>            int count=-1;
>>>              try{
>>>                conn=source.getConnection();
>>>
>>>       PreparedStatement st = conn.prepareStatement("INSERT INTO test
>>> values('P1','P2')");
>>>            count = st.executeUpdate();
>>>
>>>       st.close();
>>>            conn.commit();
>>>       conn.close();
>>>          }
>>>     catch (SQLException ex) {
>>>        count=0;
>>>       ex.printStackTrace();
>>>     }
>>>        return count;
>>>     }//End of Insert Method
>>>               public static void main(String args[]){
>>>                       ConPool cp=new ConPool();
>>>         cp. setPool();
>>>         int sucess_flag=cp.insertDatas();
>>>         System.out.println("Sucess"+sucess_flag);
>>>                /**
>>>           * Upto this level the Connection pooling is working fine .
>>>           * But if this Swing Component is added then it creates new
>>> Connection
>>>           * which is even more than the intial connection of the pool..
>>>          *  We have to kill the application (System.exit(0))to
>>> remove the Connection
>>>          ** But on commenting line :105 "Swingline " the Pool is
>>> working fine..
>>>                  */
>>>
>>> javax.swing.JOptionPane.showMessageDialog(null,"VENBRO-ERODE","MESSAGE",1);//
>>> Swing line 105
>>>                 }
>>>
>>> }//End of the class
>>> ##########################################################################################
>>>
>>> ###########################################################################################
>>>
>>>
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