Requesting explanation on process DBCP takes

[javawanabe]

Hi all,
I am trying to implement DBCP to a DB2 database on Tomcat 4.1.X and am having a few problems.

I can successfully connect directly (no DBCP) from within my code using the supplied DB2 driver, so I don't think there are any issues with either my version of Tomcat or of the DBCP jar or the DB2 driver.

However, using DBCP is proving more difficult. I have configured my web.xml and server.xml files accordingly. I then created an application listener which retrieves the info via JNDI and places my DAO objects into the application context. This too appears to wok fine, as I do successfully retrieve a generic datasource object.

But, when I then try the getConnection() method, I receive a 'cannot load driver class null' error. Obviously, something is nsf with that stage.

So I guess my questions are:

1- Is the pool actually being created successfully? Does it not use the driver to actually create the pool?
2- Am I possibly running into a scope issue?

Any info appreciated.

JW

 

[sedj]

Sounds like DBCP cannot find the driver you wish to use - where/how have you specified the driver for DBCP to use ? Perhaps post your config relating to the DBCP config.

--------------------------------------------------
Free Database Connection Pooling Software

http://www.primrose.org.uk

 

[javawanabe]

Hi again,
I finally have a bit of time to get back to this. To recap, I am trying to get DBCP connection pooling to work with Tomcat 4.1.24 and DB2 8.X. I can connect directly, but whenever I try to use DBCP, I receive a "Cannot load driver class 'null'" error. The DB2 and JNDI jar files are located in <tomcat-root>\common\lib.

This code snippet works:
...
String url = "jdbc:db2://myserver:50000/mydb";
String user = "test";
String pass = "password";
Class.forName("com.ibm.db2.jcc.DB2Driver");
Connection conn = DriverManager.getConnection(url,user,pass);
Statement stmt = conn.createStatement();
ResultSet myRs = stmt.executeQuery("select * from myTable");
...

This leads me to believe that:
a) My driver is fine and jar file location is ok
b) My login credentials are fine
I use the same driver and connection info in my DBCP config.

-------------------------------------------
Now when I try to use DBCP, this code snippet does NOT work.
...
Context jndiCtx = new InitialContext();
Context ctx = (Context) jndiCtx.lookup("java:comp/env");
DataSource ds = (DataSource) ctx.lookup("jdbc/mydb");
Connection conn = ds.getConnection();
Statement stmt = conn.createStatement();
ResultSet myRs = stmt.executeQuery("select * from myTable");
...

Tomcat does not throw any errors at startup in any logs and when I execute the above code, the DataSource retrieved (ds) is not null and a getClassName() call reveals a generic commons DataSource object. However, once it gets to the getConnection() method, the evil "Cannot load driver class 'null'" error occurs.

I tried messing around with the JNDI entries to prove that was OK, and as expected I get a naming error if I put a wrong value. This tells me that the "lookup" portion works, yes?

Here are the relevant server.xml and the web.xml entries:

------------------------------------------------------
server.xml (note: I also tried it without the factory param)
------------------------------------------------------
...
<Context...>
<Resource name="jdbc/mydb" scope="Shareable" type="javax.sql.DataSource" auth="Container" />

<Resourceparams name="jdbc/mydb">
<parameter>
<name>factory</name>
<value>org.apache.commons.dbcp.BasicDataSourceFactory</value>
</parameter>
<parameter>
<name>username</name>
<value>test</value>
</parameter>
<parameter>
<name>password</name>
<value>password</value>
</parameter>
<parameter>
<name>driverClassName</name>
<value>com.ibm.db2.jcc.DB2Driver</value>
</parameter>
<parameter>
<name>url</name>
<value>jdbc:db2://myserver:50000/mydb</value>
</parameter>
</Resourceparams>
</Context>

------------------------------------------------------
web.xml
------------------------------------------------------
...
<resource-ref>
<resource-ref-name>jdbc/mydb<resource-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
</resource-ref>


So, that is pretty much it. I have consulted 2 books, countless websites, and would appreciate any help.

Thanks

JW

 

[sedj]

I never got on with DBCP ...
Have you tried this tutorial ?

http://jakarta.apache.org/tomcat/tomcat-4.1-doc/printer/jndi-datasource-examples-howto.html

--------------------------------------------------
Free Database Connection Pooling Software

http://www.primrose.org.uk

 

[alexander1113]

I think i know what the problem is javawanabe. It worked for me but keep in mind im using tomcat 5.0.28 and mysql 4.1.

In this:

<Context...>
<Resource name="jdbc/mydb" scope="Shareable" type="javax.sql.DataSource" auth="Container" />

<Resourceparams name="jdbc/mydb">
<parameter>
<name>factory</name>
<value>org.apache.commons.dbcp.BasicDataSourceFactory</value>
</parameter>
<parameter>
<name>username</name>
<value>test</value>
</parameter>
<parameter>
<name>password</name>
<value>password</value>
</parameter>
<parameter>
<name>driverClassName</name>
<value>com.ibm.db2.jcc.DB2Driver</value>
</parameter>
<parameter>
<name>url</name>
<value>jdbc:db2://myserver:50000/mydb</value>
</parameter>
</Resourceparams>
</Context>

needs to be changed. It looks like tomcat doesn't read the ResourceParams tag. So eliminate it altogether. So you can do the following:

<Context...>
<Resource name="jdbc/mydb"
scope="Shareable"
type="javax.sql.DataSource"
auth="Container"
username="test"
password="password"
driverClassName="com.ibm.db2.jcc.DB2Driver"
url="jdbc:db2://myserver:50000/mydb"/>

</Context>

hopefully this solves it. Do keep us updated.