Re: Tomcat filter to overwrite the requestURL of incoming httprequest object

[Martin Bromley]

You have to wrap the HttpServletRequest with a class that overrides the methods 
relating to the URI.  I've attached an abstract class that I wrote to make this 
a bit easier.

You will have to implement the rewriteURL method to do the necessary String 
parsing.

Then in your filter doFilter:

chain.doFilter(new WrappedRequest(request), response);

(assuming you've written WrappedRequest - that extends the abstract class I've 
attached).

Good luck.
Martin

PS You're question actually has nothing to do with Tomcat specifically...

Jaynika Barot wrote:

hi all,

I want to write a filter which will overwrite the request URL in
incoming httprequest.

if incoming request's URI contains *./myservletName/extra1/extra2.*

I want to reset it to *./myservletName?param1=extra1&param2=extra2 and
pass this request object to subsequent processing (filter chain).

Is it possible to do?? If so how?

thx,
Jaynika

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package com.mbromley.util.servlet;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

/** This enables the URLs in an HttpServletRequest to be consistently rewritten.
 * This needs to be extended for it to do anything useful.  At least one of the
 * rewriteURL methods needs to be overridden.
 */
public abstract class URLRewritingRequestWrapper 
                extends HttpServletRequestWrapper {
        
        public URLRewritingRequestWrapper(
                        final HttpServletRequest request) {
                super(request);
        }
        
        @Override
        public final String getPathInfo() {
                return getPossiblyNull(super.getPathInfo());
        }
        
        @Override
        public final String getPathTranslated() {
                return getPossiblyNull(super.getPathTranslated());
        }
        
        @Override
        public final String getRequestURI() {
                return rewriteURL(super.getRequestURI());
        }
        
        @Override
        public final StringBuffer getRequestURL() {
                return rewriteURL(super.getRequestURL());
        }
        
        @Override
        public final String getServletPath() {
                return rewriteURL(super.getServletPath());
        }
        
        private String getPossiblyNull(final String s) {
                if (s == null) {
                        return null;
                }
                return rewriteURL(s);
        }
        
        /** Subclasses can override this if they can improve efficiency by 
rewriting
         * a StringBuffer.  By default this calls the other method and creates 
a new
         * StringBuffer from the result.
         */
        protected StringBuffer rewriteURL(final StringBuffer sB) {
                return new StringBuffer(rewriteURL(sB.toString()));
        }
        
        protected abstract String rewriteURL(final String url);
        
        @Override
        public String toString() {
                return super.toString() + " wrapping " + 
getRequest().toString();
        }
        
}

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