Existing Servlet Proxy for J2EE engine [like tomcat ]

*_ 1) J2EP_* : J2EP is a reverse proxy running on a J2EE engine. The proxy is written in java and was originally designed with Tomcat in mind, but any engine should work fine. A set of basic mapping rules are included for reverse proxing.
A set of servers is specified to be used as mappings between the proxy and Webpages. The servers all need to include a rule that is used to match any incoming request. The rules are there to decide what server to use for each request. A round robin cluster of servers is made for servicing the requests.

Link: http://sourceforge.net/projects/j2ep

*_ 2) Noodle_* : Noodle is a set of Java classes for transparently making arbitrary changes to an HTTP request and response. You can use Noodle to create a servlet that, on every HTTP request, runs Java 'filters' that you define on the request, sends the new request off to another web server, and streams the resulting response through another set of filters.

Link: http://noodle.tigris.org/

*_ 3) Http Proxy Servlet_* : a simple Java servlet written to allow Tomcat and Apache to both appear to occupy port 80

Link: http://edwardstx.net/wiki/Wiki.jsp?page=HttpProxyServlet

+ * These are only some of the existing proxies.* +

References :

[1] J2EP documentation.

[2] http://noodle.tigris.org/, “home page – noodle”.

[3] http://edwardstx.net/wiki/Wiki.jsp?page=HttpProxyServlet, “ Http proxy Servlet – main page”.