[opencms-dev] Removing /opencms by a Filter class (web.xml)

[Peter Birchmeier]

Hi all,

My situation is: I'm using an OpenCms instance on a ISP server, so it's 
difficult for me to update http.conf-rewrite statements. When I started 
recently with the installation of jforum which should be included into the 
same context, I realised that I would have to find another approach to solve 
the path rewriting issue.

By chance i had the idea to use a Filter class that catches all requests to 
the tomcat context and "rewrites" the uris by forwarding the requests to 
other pathes.

Here's a basic example how it would look like:

public class ForwarderFilter implements Filter {
..
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		try {
			HttpServletRequest req = (HttpServletRequest) request;
			String uri = req.getRequestURI(); // e.g. /forum/list.page

			int pos1 = 1, pos2 = uri.indexOf("/", pos1);
			if ( pos != -1 ) {
				String part = uri.substring( pos1, pos2 );
				if ( part.equals( "forum" ) ) {
					chain.doFilter(request, response);
					return;
				}
			}
			String forward = "/opencms" + uri;
			RequestDispatcher dispatcher = request.getRequestDispatcher(forward);
			dispatcher.forward(request, response);
		} catch ( Exception e ) { chain.doFilter(request, response); }
	}
...
}

and the web.xml directives:
	<filter>
		<filter-name>ForwarderFilter</filter-name>
		<filter-class>.....ForwarderFilter</filter-class>
	</filter>
	<filter-mapping>
		<filter-name>ForwarderFilter</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>


My main question is now: Is this a PERFORMANCE problem?
I haven't tested this method 100% but it looks promising. At the moment, I 
go the bidirect way, meaning, Apache is rewriting everything to /opencms, 
and my ForwarderFilter removes /opencms if necessary...
If this approach hasn't got significant performance issues, I would greatly 
prefer it over all others, in my situation of course, due to the fact that I 
can easily change the filter class and do not have to ask the ISP everytime. 
Additionally, I would be able to realise a fine grained rewriting (what I 
couldn't achieve in Apache 1.3)...

Thanks for your opinion,
regard Peter

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