RE: [Proxool-developer] Release 0.5

[Bill H. <bi...@lo...>]

Hi Martin,

On Wed, 2002-12-04 at 18:58, Martin Crawford wrote:

> Just upgraded to proxool-0.5 on a webapp using tomcat 4.0. I'm using the Sun
> Java SDK 1.4.0.
> 
> Everything worked fine with proxool-0.4, but the upgrade throws the
> following exception:
> 
> java.lang.ClassCastException: $Proxy2
> 	at $Proxy1.createStatement(Unknown Source)

Knowing the line that it occurred on would be really handy. Would you
mind picking up this jar file that is compiled with debug information:

http://proxool.sourceforge.net/download/proxool-cvs-debug.jar

Or, failing that, compile from source. Then I will know what line is
causing the problem. (Maybe we should create all the JARs with debug
information in until we get to 1.0...)

> I've attached my driver initialisation code 

Which looks fine.

> The stack trace shows that my exception occurs when calling
> Connection.createStatement(). 

The createStatement method is called a lot during our unit tests (as
you'd expect) and it seems to work fine.

> Perhaps a VM or JDBC version issue? 

I think the VM should be okay. What JDBC driver are you using? 

>   try {
>     // Register the JDBC driver
>     Class.forName(sJdbcDriver);
>   } catch (Exception e) {
>     throw new SQLException("Cannot find JDBC driver: " + sJdbcDriver);
>   }

For what it's worth, Proxool registers the delegate JDBC driver for you.
But it doesn't do any harm to do it twice.

---

I've had a quick review of the code that could be responsible and I have
tried doing the creation of the Statement proxy a slightly different
way:

diff -r1.5 ProxyFactory.java
54c54,55
<         return
Proxy.newProxyInstance(delegate.getClass().getClassLoader(),
delegate.getClass().getInterfaces(), new ProxyStatement(delegate,
connectionPool,
proxyConnection, sqlStatement));
---
>         Class[] interfaces = {Statement.class};
>         return
Proxy.newProxyInstance(delegate.getClass().getClassLoader(), interfaces,
new ProxyStatement(delegate, connectionPool, proxyConnection,
sqlStatement));

I have built another JAR that includes that experimental fix:

http://proxool.sourceforge.net/download/proxool-crawford.jar

Let me know if that fixes it. Or if it doesn't, the full stack trace for
the ClassCastException.

Regards,
Bill