RegexPipeline.java

/*
 * Copyright (C) 2009-2010, Google Inc. and others
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0 which is available at
 * https://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

package org.eclipse.jgit.http.server.glue;

import static javax.servlet.http.HttpServletResponse.SC_NOT_FOUND;
import static org.eclipse.jgit.http.server.glue.MetaFilter.REGEX_GROUPS;

import java.io.IOException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import javax.servlet.Filter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Selects requests by matching the URI against a regular expression.
 * <p>
 * The pattern is bound and matched against the path info of the servlet
 * request, as this class assumes it is invoked by {@link MetaServlet}.
 * <p>
 * If there are capture groups in the regular expression, the matched ranges of
 * the capture groups are stored as an array of modified HttpServetRequests,
 * into the request attribute {@link MetaFilter#REGEX_GROUPS}. Using a capture
 * group that may not capture, e.g. {@code "(/foo)?"}, will cause an error at
 * request handling time.
 * <p>
 * Each servlet request has been altered to have its {@code getServletPath()}
 * method return the original path info up to the beginning of the corresponding
 * capture group, and its {@code getPathInfo()} method return the matched text.
 * A {@link RegexGroupFilter} can be applied in the pipeline to switch the
 * current HttpServletRequest to reference a different capture group before
 * running additional filters, or the final servlet.
 * <p>
 * Note that for {@code getPathInfo()} to start with a leading "/" as described
 * in the servlet documentation, capture groups must actually capture the
 * leading "/".
 * <p>
 * This class dispatches the remainder of the pipeline using the first capture
 * group as the current request, making {@code RegexGroupFilter} required only
 * to access capture groups beyond the first.
 */
class RegexPipeline extends UrlPipeline {
    static class Binder extends ServletBinderImpl {
        private final Pattern pattern;

        Binder(String p) {
            pattern = Pattern.compile(p);
        }

        Binder(Pattern p) {
            pattern = p;
        }

        @Override
        UrlPipeline create() {
            return new RegexPipeline(pattern, getFilters(), getServlet());
        }
    }

    private final Pattern pattern;

    RegexPipeline(final Pattern pattern, final Filter[] filters,
            final HttpServlet servlet) {
        super(filters, servlet);
        this.pattern = pattern;
    }

    @Override
    boolean match(HttpServletRequest req) {
        final String pathInfo = req.getPathInfo();
        return pathInfo != null && pattern.matcher(pathInfo).matches();
    }

    @Override
    void service(HttpServletRequest req, HttpServletResponse rsp)
            throws ServletException, IOException {
        final String reqInfo = req.getPathInfo();
        if (reqInfo == null) {
            rsp.sendError(SC_NOT_FOUND);
            return;
        }

        final Matcher cur = pattern.matcher(reqInfo);
        if (!cur.matches()) {
            rsp.sendError(SC_NOT_FOUND);
            return;
        }

        final String reqPath = req.getServletPath();
        final Object old = req.getAttribute(REGEX_GROUPS);
        try {
            if (1 <= cur.groupCount()) {
                // If there are groups extract every capture group and
                // build a request for them so RegexGroupFilter can pick
                // a different capture group later. Continue using the
                // first capture group as the path info.
                WrappedRequest[] groups = new WrappedRequest[cur.groupCount()];
                for (int groupId = 1; groupId <= cur.groupCount(); groupId++) {
                    final int s = cur.start(groupId);
                    final String path, info;

                    path = reqPath + reqInfo.substring(0, s);
                    info = cur.group(groupId);
                    groups[groupId - 1] = new WrappedRequest(req, path, info);
                }
                req.setAttribute(REGEX_GROUPS, groups);
                super.service(groups[0], rsp);

            } else {
                // No capture groups were present, service the whole request.
                final String path = reqPath + reqInfo;
                final String info = null;
                super.service(new WrappedRequest(req, path, info), rsp);
            }
        } finally {
            if (old != null)
                req.setAttribute(REGEX_GROUPS, old);
            else
                req.removeAttribute(REGEX_GROUPS);
        }
    }

    /** {@inheritDoc} */
    @Override
    public String toString() {
        return "Pipeline[regex: " + pattern + " ]";
    }
}