Servlet Filter for JAX-RS content negotiation which fixes WebKit Accept header and adds extension support

AcceptFilter.java

package org.example.www.filters;

import java.io.IOException;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;

/**
 * Modifies Accept headers and allows URL extensions to improve JAX-RS content negotiation
 * Adds "Vary: accept" header to response
 * 
 * Adapted from: http://www.zienit.nl/blog/2010/01/rest/control-jax-rs-content-negotiation-with-filters
 */
public class AcceptFilter implements Filter {

	private final Map<String,String> extensions = new HashMap<String,String>();

	@SuppressWarnings("unchecked")
	public void init(FilterConfig config) throws ServletException {
		Enumeration<String> exts = config.getInitParameterNames();
		while (exts.hasMoreElements()) {
			String ext = exts.nextElement();
			if (ext != null && !ext.isEmpty()) {
				this.extensions.put("."+ext.toLowerCase(), config.getInitParameter(ext));
			}
		}
	}

	public void destroy() {}

	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
		HttpServletRequest httpRequest = (HttpServletRequest)request;
		String uri = httpRequest.getRequestURI();
		String ext = this.getExtension(uri);
		String accept = this.extensions.get(ext);

		if (accept == null) {
			// This workaround may no longer needed with the ";qs=2" answer
			// http://stackoverflow.com/questions/5250923/http-content-negotiation-conflicts-in-jax-rs-jersey/5536837#5536837

			accept = httpRequest.getHeader("accept");
			if (accept != null && accept.indexOf("text/html") > 0) {
				// patch WebKit-style Accept headers by elevating "text/html"
				accept = "text/html,"+accept;
				request = new RequestWrapper(httpRequest, uri, accept);
			}

		} else {
			// remove extension and remap the Accept header
			uri = uri.substring(0, uri.length() - ext.length());
			request = new RequestWrapper(httpRequest, uri, accept);
		}

		// add "Vary: accept" to the response headers
		HttpServletResponse httpResponse = (HttpServletResponse)response;
		httpResponse.addHeader("Vary", "accept");

		chain.doFilter(request, response);
	}

	private String getExtension(String path) {
		int index = path.lastIndexOf('.');
		if (index < 0 || path.lastIndexOf('/') > index) {
			return "";
		}

		return path.substring(index);
	}

	private static class RequestWrapper extends HttpServletRequestWrapper {

		private final String uri;
		private final String accept;

		public RequestWrapper(HttpServletRequest request, String uri, String accept) {
			super(request);

			this.uri = uri;
			this.accept = accept;
		}

		@Override
		public String getRequestURI() {
			return this.uri;
		}

		@Override
		public Enumeration getHeaders(String name) {
			if (!"accept".equalsIgnoreCase(name)) {
				return super.getHeaders(name);
			}

			Vector<String> values = new Vector<String>(1);
			values.add(this.accept);
			return values.elements();
		}
	}
}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
	xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
	<filter>
		<filter-name>accept-filter</filter-name>
		<filter-class>org.example.www.filters.AcceptFilter</filter-class>
		<init-param>
			<param-name>html</param-name>
			<param-value>text/html</param-value>
		</init-param>
		<init-param>
			<param-name>xml</param-name>
			<param-value>application/xml</param-value>
		</init-param>
		<init-param>
			<param-name>json</param-name>
			<param-value>application/json</param-value>
		</init-param>
	</filter>
	<filter-mapping>
		<filter-name>accept-filter</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>
</web-app>

At line 52 you have "Very"... when comment says "Vary".. IIRC comment is correct!
Also I'd not, prefix extensions hashmap key with dots and convert returned ext to lowercase without the dot, so .XML or .xml would work...

ie.
Line 24:
this.extensions.put(ext.toLowerCase(), config.getInitParameter(ext));
Line 46:
uri = uri.substring(0, uri.length() - ext.length()-1);

private String getExtension(String path) {
	String result = "";
	int index = path.lastIndexOf('.');
	if (!(index < 0 || path.lastIndexOf('/') > index)) {
		result =  path.substring(index+1).toLowerCase();
	}
	return result;
}