com.pushinginertia.commons.net.util.HttpServletRequestUtils.java Source code

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Here is the source code for com.pushinginertia.commons.net.util.HttpServletRequestUtils.java

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/* Copyright (c) 2011-2013 Pushing Inertia
 * All rights reserved.  http://pushinginertia.com
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.pushinginertia.commons.net.util;

import com.pushinginertia.commons.core.validation.ValidateAs;
import com.pushinginertia.commons.net.IpAddress;
import com.pushinginertia.commons.net.IpAddressUtils;
import org.apache.http.HttpHeaders;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.servlet.http.HttpServletRequest;
import java.util.Enumeration;
import java.util.StringTokenizer;

/**
 * Utility methods for extracting information out of a {@link javax.servlet.http.HttpServletRequest}.
 */
public final class HttpServletRequestUtils {
    private static final Logger LOG = LoggerFactory.getLogger(HttpServletRequestUtils.class);

    public static final String HOST = "Host";
    public static final String X_FORWARDED_HOST = "X-Forwarded-Host";
    public static final String X_FORWARDED_FOR = "X-Forwarded-For";

    private HttpServletRequestUtils() {
    }

    /**
     * Parses the host name from the request.
     * @param req request received from the user agent
     * @return null if unable to parse
     */
    public static String getRequestHostName(final HttpServletRequest req) {
        // maybe we are behind a proxy
        String header = req.getHeader(X_FORWARDED_HOST);
        if (header != null) {
            // we are only interested in the first header entry
            header = new StringTokenizer(header, ",").nextToken().trim();
        }
        if (header == null)
            header = req.getHeader(HOST);

        return header;
    }

    /**
     * Identifies the remote IP address from a request, even if the application is running behind a forwarding agent.
     * @param req request received from the user agent
     * @return null if the ip address cannot be identified
     */
    public static String getRemoteIpAddress(final HttpServletRequest req) {
        ValidateAs.notNull(req, "req");

        final String xForwardedFor = req.getHeader(X_FORWARDED_FOR); // method is case insensitive
        if (xForwardedFor == null) {
            return req.getRemoteAddr();
        }

        final IpAddress remoteIpAddress = getRemoteIpAddressFromXForwardedFor(xForwardedFor);
        if (IpAddressUtils.isNonRoutable(remoteIpAddress)) {
            final String remoteAddr = req.getRemoteAddr();
            LOG.warn(X_FORWARDED_FOR + " reports a non-routable IP [" + xForwardedFor
                    + "]. This should always report the remote IP address. Servlet reports remote addr ["
                    + remoteAddr + "]. Full request:\n" + toString(req));
            if (!IpAddressUtils.isNonRoutable(new IpAddress(remoteAddr))) {
                // return the ip address reported by the servlet if it's routable
                return remoteAddr;
            }
        }
        return remoteIpAddress.getIpAddress();
    }

    private static IpAddress getRemoteIpAddressFromXForwardedFor(final String xForwardedFor) {
        if (xForwardedFor.contains(",")) {
            // sometimes the header is of form: client ip,proxy 1 ip,proxy 2 ip,...,proxy n ip
            // we just want the client
            final String first = xForwardedFor.split(",")[0].trim();
            return new IpAddress(first);
        }

        return new IpAddress(xForwardedFor);
    }

    /**
     * Identifies the user agent from a request.
     * @param req request received from the user agent
     * @return null if no user agent in the request
     */
    public static String getUserAgent(final HttpServletRequest req) {
        ValidateAs.notNull(req, "req");
        return req.getHeader(HttpHeaders.USER_AGENT);
    }

    /**
     * Converts all of the headers in a request to a newline-separated string of name-value pairs. This is required
     * because not all implementations of {@link javax.servlet.http.HttpServletRequest} implement the toString method.
     * @param req request received from the user agent
     * @return null if req is null
     */
    public static String toString(final HttpServletRequest req) {
        ValidateAs.notNull(req, "req");

        final StringBuilder sb = new StringBuilder();
        for (Enumeration<String> headerNames = req.getHeaderNames(); headerNames.hasMoreElements();) {
            final String headerName = headerNames.nextElement();
            for (Enumeration<String> headers = req.getHeaders(headerName); headers.hasMoreElements();) {
                final String value = headers.nextElement();
                sb.append(headerName).append('=').append(value).append('\n');
            }
        }
        return sb.toString();
    }
}