JNDI ClassCastException

Question

I am attempting to use JNDI with a custom DataSource called CEDataSource. From my understanding for this to work I would have to create a custom factory as well.

So I created a custom factory that would return the CEDataSource object but now when I attempt to use this in Java with

Context initCtx = new InitialContext();
Context envCtx = (Context) initCtx.lookup("java:comp/env");
// Look up our data source
   CEDataSource ds = (CEDataSource)envCtx.lookup("jdbc/cePu");

I get the exception ClassCastException "CEDataSource cannot be mapped to CEDataSource". I added the CEDataSource and the CEDataSourceFactory to the TOMCAT/lib folder as well as referenced this same jar on my deployed application.

Any help would be greatly appreciated on why this possible error may occur. Thanks

Code seems right. you could show your context.xml. – 卢声远 Shengyuan Lu Jan 18 '11 at 01:47 — 卢声远 Shengyuan Lu, Jan 18 '11 at 01:47

score 5 · Accepted Answer · answered Jan 18 '11 at 07:54

5

"CEDataSource cannot be mapped to CEDataSource" seems to point to the fact that it's not the same "CEDataSource" in both places.

What could be different is the classloader and this usually happens if you have the same jars/.class(es) in multiple locations.

Do you have multiple copies of your jar? Try to have a single copy, maybe in the shared tomcat lib so it's loaded by the same classloader no matter from where you access it from.

answered Jan 18 '11 at 07:54

Cristian Vat

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Same class coming from different classloader is actually not the same class and can not be castor assigned to it. Usually one has to place such custom class into server wide classloader and ensure that applications delegate to it ( could be tricky in some environments ) – Konstantin Pribluda Sep 03 '12 at 13:20

Alain Pannetier · Answer 2 · 2011-01-18T04:11:15.037

It is actually not too difficult to start Tomcat under an Eclipse debug session (just put all the Bootstrap.jar in a project and add the System properties in the JVM parameters). II've done that many times, if only to dissect the bowels of that feline. Once this is done you can break on the class cast exception of the JNDI connection factory and you will then be able to see if your factory is called or not.

From what I remember Tomcat uses the DBCP DataSource. Actually repackaged under com.apache.tomcat.dbcp.dbcp.DataSource (IIRC).

So I would not be surprised if this is what you end up with as a result of your look-up.

With hindsight, I now realize I also forgot to mention that if any underlying class (for instance a JDBC driver) needed to create the instance of your CEDataSource is missing you also get this ClassCastException. Fair enough, but you always focus on the class itself and not on the other jars...

score 0 · Answer 3 · answered Jan 18 '11 at 07:04

CEDataSource ds = (CEDataSource)envCtx.lookup("jdbc/cePu");

The lookup you are doing on jdbc/cePu is not of class type CEDataSource , it belongs to some other class type, that is why you are getting class cast exception. if you could show me the configuration for jdbc/cePu that would be helpful.

JNDI ClassCastException

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