java - How can I retrieve IP address from HTTP header in Java

Question

I am curious if there is any library that handles already this kind of stuff, or I have to do it by myself once again. So, the thing is I want to get IP address field from the visitors HTTP header request on my server, and do the whole thing in Java? Any help would be nice. Thanks in advance.

Answer 1

Use the getHeader(String Name) method of the javax.servlet.http.HttpServletRequest object to retrieve the value of Remote_Addr variable. Here is the sample code:

String ipAddress = request.getHeader("Remote_Addr");

If this code returns empty string, then use this way:

String ipAddress = request.getHeader("HTTP_X_FORWARDED_FOR");

if (ipAddress == null) {
    ipAddress = request.getRemoteAddr();
}

Answer 2

即使有一个被高度支持的公认答案，我还是想提出一个替代方案并指出公认答案的缺点。

request.getHeader("Remote_Addr")指定返回与完全相同request.getRemoteAddr()。因此，两者都检查是没有意义的。另请注意，这getRemoteAddr是一种javax.servlet.ServletRequest（即与 HTTP 无关的）whilegetHeader方法javax.servlet.http.HttpServletRequest。

此外，一些代理使用Client-IP而不是X-Forwarded-For. 有关讨论，请参阅https://stackoverflow.com/a/7446010/131929。

我不知道使用HTTP_X_FORWARDED_FORoverX-Forwarded-For的可靠性如何。在 Java 中，我宁愿使用直接的简短形式。有关讨论，请参阅https://stackoverflow.com/a/3834169/131929。大写/小写没有区别，因为getHeader被指定为区分大小写。

Java 替代方案

public final class ClientIpAddress {

  // CHECKSTYLE:OFF
  // https://stackoverflow.com/a/11327345/131929
  private static Pattern PRIVATE_ADDRESS_PATTERN = Pattern.compile(
      "(^127\\.)|(^192\\.168\\.)|(^10\\.)|(^172\\.1[6-9]\\.)|(^172\\.2[0-9]\\.)|(^172\\.3[0-1]\\.)|(^::1$)|(^[fF][cCdD])",
      Pattern.CANON_EQ);
  // CHECKSTYLE:ON

  private ClientIpAddress() {
  }

  /**
   * Extracts the "real" client IP address from the request. It analyzes request headers
   * {@code REMOTE_ADDR}, {@code X-Forwarded-For} as well as {@code Client-IP}. Optionally
   * private/local addresses can be filtered in which case an empty string is returned.
   *
   * @param request HTTP request
   * @param filterPrivateAddresses true if private/local addresses (see
   * https://en.wikipedia.org/wiki/Private_network#Private_IPv4_address_spaces and
   * https://en.wikipedia.org/wiki/Unique_local_address) should be filtered i.e. omitted
   * @return IP address or empty string
   */
  public static String getFrom(HttpServletRequest request, boolean filterPrivateAddresses) {
    String ip = request.getRemoteAddr();

    String headerClientIp = request.getHeader("Client-IP");
    String headerXForwardedFor = request.getHeader("X-Forwarded-For");
    if (StringUtils.isEmpty(ip) && StringUtils.isNotEmpty(headerClientIp)) {
      ip = headerClientIp;
    } else if (StringUtils.isNotEmpty(headerXForwardedFor)) {
      ip = headerXForwardedFor;
    }
    if (filterPrivateAddresses && isPrivateOrLocalAddress(ip)) {
      return StringUtils.EMPTY;
    } else {
      return ip;
    }
  }

  private static boolean isPrivateOrLocalAddress(String address) {
    Matcher regexMatcher = PRIVATE_ADDRESS_PATTERN.matcher(address);
    return regexMatcher.matches();
  }
}

PHP 替代方案

function getIp()
{
    $ip = $_SERVER['REMOTE_ADDR'];

    if (empty($ip) && !empty($_SERVER['HTTP_CLIENT_IP'])) {
        $ip = $_SERVER['HTTP_CLIENT_IP'];
    } elseif (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
        // omit private IP addresses which a proxy forwarded
        $tmpIp = $_SERVER['HTTP_X_FORWARDED_FOR'];
        $tmpIp = filter_var(
            $tmpIp,
            FILTER_VALIDATE_IP,
            FILTER_FLAG_IPV4 | FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE
        );
        if ($tmpIp != false) {
            $ip = $tmpIp;
        }
    }
    return $ip;
}