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Thread: jdbc connection

jdbc connection

From
"michel verplancke"
Date:
Please can you help me
 
I try to connect a java application from a windows W2K to a Linux postgresql with a very simple query, which is "select * from table".
 
The error message is "connection is closed, operation is not permitted"
 
here is the class definition
 
 import java.sql.*;
 
public class JdbcQuery {
    private Connection con = null;
    public int recordnb = 0;
    private Statement stmt = null;
    private ResultSet result = null;
 
    private String driver = "org.postgresql.Driver";
    private String url = "jdbc:postgresql://COMPUTERNAME:5432/DATABASE";
    private String username = "michels";
    private String password = "";
 
boolean ConnectPostgresql(String Valquery) { 
 try   // Attempt to load the JDBC driver
     {     
     Class.forName(driver);
     } 
    catch( Exception e )  // error
     {
  JOptionPane.showMessageDialog(null, "Failed to load the following JDBC driver : " + e.getMessage(), "Error ! ", JOptionPane.PLAIN_MESSAGE);
  return false;
      }
    try
     {
  con = DriverManager.getConnection ( url, username, password);
  stmt = con.createStatement();
     }
    catch ( Exception e)
     {
   JOptionPane.showMessageDialog(null, "Problems connecting to " + url + ":" + e.getMessage(), "Error ! ", JOptionPane.PLAIN_MESSAGE);
  return false;
   }
      if( con != null)
       {
         try { con.close(); }
         catch( Exception e2 ) {}
      }
    try
     {
  result = stmt.executeQuery(Valquery);           IT's HERE THAT I GET THE PROBLEM !!!!!!!
     }
    catch (Exception e) 
  {
   JOptionPane.showMessageDialog(null, "Problems with resultset : " + e.getMessage(), "Error ! ", JOptionPane.PLAIN_MESSAGE);
  return false;
  }
 return true;
  }
 
int GetRecordnb()
 {
     try
     {
  result.last();
  recordnb = result.getRow();
  result.beforeFirst();
 
     } // end try
    catch ( Exception e)
     {
        System.err.println( "problems in GetRecordnb managing resultset" );
        System.err.println( e.getMessage() );
      if( con != null)
       {
         try { con.close(); }
         catch( Exception e2 ) {}
      }
     } // end catch 
  return recordnb;
 }
 
// alternative (donne le même résultat que la manière précédente)
 
// System.out.println(result.getFetchSize()); 
 
ResultSet GetRecordData()
 {
 return result;
 }
 
void CloseConnection()
 {
  try { stmt.close(); }
        catch( Exception e ) {}
        try { con.close(); }
        catch( Exception e ) {}
       }
 
} // end class
 
If I try the same query from the Cygwin psql it works !!
 
Does somebody have an idea ?
 
Thanks
 
  
 

Re: jdbc connection

From
"Paul Stead"
Date:
Just a real quick look, but it seems to me that you're closing your connection before you use it....
 
      if( con != null) 
       {
         try { con.close(); }                          You're closing it here
         catch( Exception e2 ) {}
      }
    try
     {
  result = stmt.executeQuery(Valquery);           IT's HERE THAT I GET THE PROBLEM !!!!!!!
     }

Re: jdbc connection

From
Abel Muiño
Date:
El dom, 19-01-2003 a las 20:46, michel verplancke escribió:
>
> The error message is "connection is closed, operation is not
> permitted"
>
    Most linux distributions ship PostgreSQL with remote access disabled.
Some even disable TCP/IP communication with the server.

    This is documented on the postgreSQL documentation.

    Check your /etc/postgresql/postgresql.conf (see if TCP/IP is enabled)
and /etc/postgresql/pg_hba.conf to see if access from your host is
allowed.
--
Abel Muiño Vizcaino