classpath issue with c3p0

Hi all,

I am trying to solve a frustrating problem with a servlet running under tomcat 6. Running under Windows there was no problems, but now after trying to move it over to OS X there are odd problems occurring.

We are using c3p0 to do connection pooling, however c3p0 is having trouble creating the database connections, it gives the following error:

java.sql.SQLException: No suitable driver

After looking at the c3p0 code, it attempts to get a reference to the driver by calling:

But this is throwing the exception.

If I place the following code into my webapp (which is copied from the c3p0 xml file im using):

It works without a problem.

Does this mean that is is not finding the com.mysql.jdbc.Driver class or is it caused by something else? I have tried copying the mysql connector jar file into tomcat_home/lib but that didn't help either.

The only other thing I can think of is the jdbcUrl being used by c3p0 is getting mangled some how, but checking that is going to be bit of a pain.

Hi Henrik and welcome to Javaranch!

Originally posted by Henrik Axelsson:
Hi all,

I am trying to solve a frustrating problem with a servlet running under tomcat 6. Running under Windows there was no problems, but now after trying to move it over to OS X there are odd problems occurring.

We are using c3p0 to do connection pooling, however c3p0 is having trouble creating the database connections, it gives the following error:

java.sql.SQLException: No suitable driver

After looking at the c3p0 code, it attempts to get a reference to the driver by calling:
driver = DriverManager.getDriver( jdbcUrl );
But this is throwing the exception.

If I place the following code into my webapp (which is copied from the c3p0 xml file im using):
DriverManager.getDriver( "jdbc:mysql://localhost/testdb" );
It works without a problem.

Does this mean that is is not finding the com.mysql.jdbc.Driver class or is it caused by something else? I have tried copying the mysql connector jar file into tomcat_home/lib but that didn't help either.

The only other thing I can think of is the jdbcUrl being used by c3p0 is getting mangled some how, but checking that is going to be bit of a pain.

Indeed you are going to have to check what the value of the jdbcUrl variable is (you obviously want it to be "jdbc:mysql://localhost/testdb"). I'm not familiar with c3p0, but is it open source? Can you modify the code to put a logger statement or two in there to get that value out?

thanks for the reply, yes it is open source, the source tree is bit of a mess though! I tried loading into netbeans but it wasn't too happy with it. I'll have to spend a bit more time on it.

Considering the same file is working fine under windows, I'm fairly certain that it is being caused by classpath/classloader issues.

I was having another problem loading the c3p0 configuration files, it was located in: project_dir/config and I was accessing it using .

This worked fine on windows, and after adding the directory to the tomcat classpath I could access it from the main servlet class using

but if i tried accessing it from another class, using

it wouldn't find the file.

In the end I move the config files into project_dir/deployment/WEB-INF/classes/config where it was found by both classes.

Now I'm not tomcat expert, but it seems to me like there are some security or classpath settings that I could be missing that is likely causing both issues. Who knows though, it could be the urls getting messed up. Argh so frustrating!

I'm pretty sure it will be the class loaders yes. The c3p0.cfg file problem you had is definitely an indication of that (the Servlet is using a different class loader to your Otherclass)

Another question, where is the value of jdbcUrl ultimately coming from? c3p0 must be reading it in from a configuration file somewhere...

The value of the jdbcUrl comes from the c3p0-config.xml file. As this is the same file that we are using under windows (where it works fine) I don't think that this would be the issue. Just to make sure, I copy/pasted the connection strings from the config file into SquirrelSQL and it didn't have a problem with them.

Ok solved the problem!

It ended up being this:
c3p0 was trying to find the configuration file using the system class loader, which doesn't have access to the /lib dir of the web app.

Because it wasn't reading the config file, when I was trying to get connections, there were no pool configurations set up. The reason I got confused it that I also parse the config file to get the pool names and actually create the pools. (c3p0 just creates the pool configs, not the actual pools).

So, if I added /project_dir/config to the class path of tomcat in the catalina.bat file it all works fine.

I'll have to check to make 100% sure but, to me this seems like an error in c3p0, it really should be using Class.class.getClassLoader().getResource(); instead of ClassLoader.getSystemResource(); I've seen that other people have had this problem with different libraries when trying to run them in web containers.

Hopefully this will save someone else wasting 2 days of their time hunting this down!

Great to hear you solved the problem and thanks for posting the solution for others to share!