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Re: Troubles with informix jdbc driver ...

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In article <slrnnejkme.456.avl@login.logic.tuwien.ac.at>,
 Andreas Leitgeb <avl@logic.at> wrote:

> Andreas Leitgeb <avl@logic.at> wrote:
> > Kevin McMurtrie <mcmurtrie@pixelmemory.us> wrote:
> >> There's too much legacy cruft and unreliable magic in DriverManager.
> >> I strongly recommend finding your driver using Class.forName(classname), 
> >> creating an instance, then calling it directly through its 
> >> java.sql.Driver interface.
> > I put this on my todo-list of things I'll experiment with.
> > For now, a coworker will prepare a simple class that will connect
> > to a selected db server (one of a few) and pick a row from some table
> > that will allow us to check whether the row comes from the right server.
> 
> I'm now that one step further, and with that test program (which is still
> far away from an <sccee>) I can now reproduce cases of mixup from within
> eclipse debugger.
> 
> Informix's Connection instance has an internal field "connInfo", which
> seems to be some kind of map that contains Properties and other stuff.
> 
> Most notably, for the thread I trapped on the wrong DB, it contained a pair
> for the original (and correct) DB-URL:
>   USERURL=jdbc:informix-sqli://machine:12345/dbA:informixserver=ifxserver
> but it also contained another pair:
>   DATABASE=dbB
> which contained a wrong database name. This one probably got mixed in from
> some other concurrent attempt to connect to dbB on the same informixserver.
> That other thread targetting dbB got its own connection (to dbB) just fine.
> Each of the threads had got an individual instance of Connection.
> 
> > It wouldn't have occurred to me to suspect DriverManager (isn't that 
> > a class of the JRE, rather than of the specific driver?), so thanks
> > for that heads-up.
> 
> Tomorrow I'll locally change the code to avoid DriverManager and instead
> deal with instances of IfxDriver directly - just for testing.
> 
> Btw., so far I need about 5 to 20 bursts (of about 10 concurrent connection
> attempts each time) to get to see the misbehaviour happening.
> 
> Thanks for caring.

Wow, I guess the Informix driver still sucks a decade later.
Here's some totally untested code to start with :)


import java.lang.ref.WeakReference;
import java.sql.Connection;
import java.sql.Driver;
import java.sql.DriverPropertyInfo;
import java.sql.SQLException;
import java.util.Properties;

public class IfxDriver implements Driver
{
   private final Class<Driver> driverClass;
   private final ThreadLocal<WeakReference<Driver>> driverCache = new ThreadLocal<WeakReference<Driver>>();

   public IfxDriver() throws SQLException
   {
      try
      {
         driverClass = (Class<Driver>) Class.forName("com.informix.jdbc.IfxDriver");
      }
      catch (ClassNotFoundException e)
      {
         throw new SQLException("Missing driver", e);
      }
   }

   private Driver getDriver() throws SQLException
   {
      final WeakReference<Driver> driverRef = driverCache.get();
      Driver driver = (driverRef != null) ? driverRef.get() : null;

      if (driver == null)
      {
         try
         {
            driver = driverClass.newInstance();
         }
         catch (InstantiationException e)
         {
            throw new SQLException(e.getMessage(), e.getCause());
         }
         catch (IllegalAccessException e)
         {
            throw new SQLException("Wrong driver class", e);
         }
         driverCache.set(new WeakReference<Driver>(driver));
      }
      return driver;
   }

   @Override
   public boolean acceptsURL(String url) throws SQLException
   {
      return getDriver().acceptsURL(url);
   }

   @Override
   public Connection connect(String url, Properties info) throws SQLException
   {
      return getDriver().connect(url, info);
   }

   @Override
   public int getMajorVersion()
   {
      try
      {
         return getDriver().getMajorVersion();
      }
      catch (SQLException e)
      {
         throw new RuntimeException(e);
      }
   }

   @Override
   public int getMinorVersion()
   {
      try
      {
         return getDriver().getMajorVersion();
      }
      catch (SQLException e)
      {
         throw new RuntimeException(e);
      }
   }

   @Override
   public DriverPropertyInfo[] getPropertyInfo(String url, Properties info) throws SQLException
   {
      return getDriver().getPropertyInfo(url, info);
   }

   @Override
   public boolean jdbcCompliant()
   {
      try
      {
         return getDriver().jdbcCompliant();
      }
      catch (SQLException e)
      {
         throw new RuntimeException(e);
      }
   }
}

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Thread

Troubles with informix jdbc driver ... Andreas Leitgeb <avl@logic.at> - 2016-03-14 13:54 +0000
  Re: Troubles with informix jdbc driver ... Marcel Mueller <news.5.maazl@spamgourmet.org> - 2016-03-14 21:23 +0100
    Re: Troubles with informix jdbc driver ... Andreas Leitgeb <avl@logic.at> - 2016-03-14 21:30 +0000
  Re: Troubles with informix jdbc driver ... Arne Vajhøj <arne@vajhoej.dk> - 2016-03-14 18:16 -0400
    Re: Troubles with informix jdbc driver ... Marcel Mueller <news.5.maazl@spamgourmet.org> - 2016-03-15 21:57 +0100
      Re: Troubles with informix jdbc driver ... Arne Vajhøj <arne@vajhoej.dk> - 2016-03-15 21:18 -0400
    Re: Troubles with informix jdbc driver ... Andreas Leitgeb <avl@logic.at> - 2016-03-15 22:25 +0000
      Re: Troubles with informix jdbc driver ... Arne Vajhøj <arne@vajhoej.dk> - 2016-03-15 21:25 -0400
  Re: Troubles with informix jdbc driver ... Kevin McMurtrie <mcmurtrie@pixelmemory.us> - 2016-03-14 21:26 -0700
    Re: Troubles with informix jdbc driver ... Andreas Leitgeb <avl@logic.at> - 2016-03-15 22:09 +0000
      Re: Troubles with informix jdbc driver ... Andreas Leitgeb <avl@logic.at> - 2016-03-16 21:37 +0000
        Re: Troubles with informix jdbc driver ... Kevin McMurtrie <mcmurtrie@pixelmemory.us> - 2016-03-16 22:36 -0700
          Re: Troubles with informix jdbc driver ... -- workaround found Andreas Leitgeb <avl@logic.at> - 2016-03-17 17:23 +0000
            Re: Troubles with informix jdbc driver ... -- workaround found Andreas Leitgeb <avl@logic.at> - 2016-03-18 11:13 +0000

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