JSONWriter is causing locks in class loader, because it always invokes Introspector.getBeanInfo(). That in turn tries to load a class with "BeanInfo" suffix in Introspector.findExplicitBeanInfo(). Such class does not exists, but we try to load it over and over again for every JSON result. Class loading involves a lock in the application server, and this causes performance issue in heavily multithreaded applications.
This could be solved by caching the BeanInfo for the classes, for which I have created a patch.
The issue is also mentioned here: