jgit/org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/glue/RegexGroupFilter.java

/*
 * Copyright (C) 2009-2010, Google Inc.
 * and other copyright owners as documented in the project's IP log.
 *
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Distribution License v1.0 which
 * accompanies this distribution, is reproduced below, and is
 * available at http://www.eclipse.org/org/documents/edl-v10.php
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
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 *
 * - Redistributions of source code must retain the above copyright
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 *   names of its contributors may be used to endorse or promote
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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package org.eclipse.jgit.http.server.glue;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

/**
 * Switch servlet path and path info to use another regex match group.
 * <p>
 * This filter is meant to be installed in the middle of a pipeline created by
 * {@link MetaServlet#serveRegex(String)}. The passed request's servlet path is
 * updated to be all text up to the start of the designated capture group, and
 * the path info is changed to the contents of the capture group.
 **/
public class RegexGroupFilter implements Filter {
	private final int groupIdx;

	/**
	 * @param groupIdx
	 *            capture group number, 1 through the number of groups.
	 */
	public RegexGroupFilter(final int groupIdx) {
		if (groupIdx < 1)
			throw new IllegalArgumentException("Invalid index: " + groupIdx);
		this.groupIdx = groupIdx - 1;
	}

	public void init(FilterConfig config) throws ServletException {
		// Do nothing.
	}

	public void destroy() {
		// Do nothing.
	}

	public void doFilter(final ServletRequest request,
			final ServletResponse rsp, final FilterChain chain)
			throws IOException, ServletException {
		final WrappedRequest[] g = groupsFor(request);
		if (groupIdx < g.length)
			chain.doFilter(g[groupIdx], rsp);
		else
			throw new ServletException("Invalid regex group " + (groupIdx + 1));
	}

	private static WrappedRequest[] groupsFor(final ServletRequest r) {
		return (WrappedRequest[]) r.getAttribute(MetaServlet.REGEX_GROUPS);
	}
}