This problem is a major performance bottleneck in Grails 2.0 applications.
Currently this problem shows up when resources plugin has been installed and used in a Grails app. (see attached screenshot)
Exceptions are relatively heavy weight in Java. Filling the stacktrace takes most of the time. Normal execution flow should never throw exceptions.
(it is possible to disable filling the stacktrace like has been done for MissingMethodExceptionNoStack, in that case the performance overhead is usually acceptable.)
The problem shows up whenever there is 2 classes sharing the same base class and when the other class is a Java class and the other one is a Groovy class (GroovyObject).
I was able to reproduce the problem with this code. Run this code in a debugger and make a breakpoint for the construction of ClassCastException.
In this example the base class is java.util.Map , the Java class is LinkedHashMap and the Groovy class is MyMap (extends LinkedHashMap).
In a Grails app the 2 different java.util.Map implementations usually triggering this problem are LinkedHashMap and GrailsParameterMap (GroovyObject).
In Grails core I've worked around some of the problem with this type of hack:
At that time I didn't have time to investigate the reason that caused the problem and just made some changes until the problem went away.