Reverse Proxy with Cache configuration problem

I would like to config an apache web server act as a reverse proxy to
internal application servers, and it works. But i would like the
apache also cache the results. I am using the disk cache mode, but I
cant see anything in the specific disk directory.

Below is the configuration:

LoadModule cache_module modules/mod_cache.so
LoadModule disk_cache_module modules/mod_disk_cache.so
LoadModule mem_cache_module modules/mod_mem_cache.so

LoadModule proxy_module modules/mod_proxy.so
LoadModule proxy_http_module modules/mod_proxy_http.so

CacheRoot "d:\webcache"
CacheEnable disk /
CacheDirLevels 2
CacheDirLength 1

ProxyRequests Off

<Proxy *>
Order deny,allow
Allow from all
</Proxy>

ProxyPass /jsp-examples http://localhost:8080/jsp-examples
ProxyPassReverse /jsp-examples http://localhost:8080/jsp-examples

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Can somebody tell me why the Cache not works? and how can we enable
caches?

Very thanks