[2.2] ThreadLocal use in PoolableProxyHandler

[Alexander Daniel]

Does somebody know why ThreadLocal is used in PoolableProxyHandler [1]  
for the componentHolder in Cocoon 2.2?

Thanks, Alex
[1] 
http://svn.apache.org/repos/asf/cocoon/trunk/core/cocoon-sitemap/cocoon-sitemap-impl/src/main/java/org/apache/cocoon/core/container/spring/avalon/PoolableFactoryBean.java