Unable to checkout connection, stack blown due to internal ClassCastException

[konrad-garus]

After upgrade from 0.9.1.2 to 0.9.2.1, the pool is unable to check out connections. It fails each time in the loop in BaseResourcePool due to unexpected ClassCastException in attemptRefurbishResourceOnCheckout, eventually blowing the stack.

Stack trace:

Exception in thread "main" java.lang.StackOverflowError
    at java.lang.Exception.<init>(Exception.java:41)
    at java.lang.RuntimeException.<init>(RuntimeException.java:43)
    at java.lang.ClassCastException.<init>(ClassCastException.java:39)
    at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$C3P0PooledConnectionNestedLockLockFetcher.getInUseLock(C3P0PooledConnectionPool.java:127)
    at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.refurbishResourceOnCheckout(C3P0PooledConnectionPool.java:298)
    at com.mchange.v2.resourcepool.BasicResourcePool.attemptRefurbishResourceOnCheckout(BasicResourcePool.java:1682)
    at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:528)
    at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:563)
    at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:563)
    at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:563)
    at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:563)
// ... and so on

The root cause seems to be:

013-05-13 06:18:12 [main] DEBUG: A resource could not be refurbished for checkout. [com.mchange.v2.c3p0.impl.C3P0PooledConnection@5a296cad]
java.lang.ClassCastException: com.mchange.v2.c3p0.impl.C3P0PooledConnection cannot be cast to com.mchange.v2.c3p0.impl.NewPooledConnection

[konrad-garus]

It only happens with usesTraditionalReflectiveProxies=true.

[swaldman]

hi,

thanks for reporting the issue. usesTraditionalReflectiveProxies is now deprecated; i don't promise to maintain the reflective proxies. nevertheless, i've fixed this issue (in github source and the current snapshot of c3p0-0.9.5-pre3.

thanks again!

[konrad-garus]

Thank you!

Is 0.9.5-preX stable and production ready? Or should it be considered alpha/experimental?

[swaldman]

I think that it is pretty solid, and would selfishly love for you to use it and report any issues.

That said, the series has not stabilized and should still be considered a bit experimental. Your safest bet is to use 0.9.2.1 with usesTraditionalReflectiveProxies=false, unless you wish to use JDBC4 features (or if you want to configure in typesafe-config/hocon format or if you want c3p0 to log through the slf4j interface).