Java获取远程IP地址:request.getRemoteAddr()警惕

request.getLocalAddr()//获取本机IP

request.getRemoteAddr()//Java获取远程IP地址:

public static String getClientAddress(HttpServletRequest request) {
String address = request.getHeader("X-Forwarded-For");
if (address != null && IpUtil.isIpAddress(address)) {
return address;
}
return request.getRemoteAddr();
}

request.getRemoteAddr():获得IP地址

System.out.println("request.getRemoteAddr(): <wbr><wbr>" <wbr><wbr>+ <wbr><wbr>request.getRemoteAddr());<wbr><wbr><wbr><br> System.out.println("request.getRemoteHost(): <wbr><wbr>" <wbr><wbr>+ <wbr><wbr>request.getRemoteHost());</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

得到的结果相同（局域网内试验的结果）。 <wbr><wbr><wbr><br> 那么getRemoteAddr()和getRemoteHost()到底有什么区别？ <wbr><wbr><wbr><br> 我的目的就是要得到发出request的机器的IP地址，到底用以上哪个方法？ <wbr><br> --------------------------------------------------------------- <wbr><br><wbr><br> 前一个是获得客户端的ip地址 <wbr><br> 后一个是获得客户端的主机名 <wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

在JSP里，获取客户端的IP地址的方法是：request.getRemoteAddr()，这种方法在大部分情况下都是有效的。但是在通过了Apache,Squid等反向代理软件就不能获取到客户端的真实IP地址了。

如果使用了反向代理软件，将http://192.168.1.110:2046/ 的URL反向代理为http://www.xxx.com/ 的URL时，用request.getRemoteAddr()方法获取的IP地址是：127.0.0.1　或　192.168.1.110，而并不是客户端的真实ＩＰ。

经过代理以后，由于在客户端和服务之间增加了中间层，因此服务器无法直接拿到客户端的 IP，服务器端应用也无法直接通过转发请求的地址返回给客户端。但是在转发请求的HTTP头信息中，增加了X－FORWARDED－FOR信息。用以跟踪原有的客户端IP地址和原来客户端请求的服务器地址。当我们访问http://www.xxx.com/index.jsp/ 时，其实并不是我们浏览器真正访问到了服务器上的index.jsp文件，而是先由代理服务器去访问http://192.168.1.110:2046/index.jsp ，代理服务器再将访问到的结果返回给我们的浏览器，因为是代理服务器去访问index.jsp的，所以index.jsp中通过request.getRemoteAddr()的方法获取的IP实际上是代理服务器的地址，并不是客户端的IP地址。

于是可得出获得客户端真实IP地址的方法一：

public String getRemortIP(HttpServletRequest request) {
<wbr><wbr><wbr><wbr>if (request.getHeader("x-forwarded-for") == null) {<br><wbr><wbr><wbr><wbr><wbr><wbr>return request.getRemoteAddr();<br><wbr><wbr><wbr><wbr>}<br><wbr><wbr><wbr><wbr>return request.getHeader("x-forwarded-for");</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr>}</wbr></wbr>

可是当我访问http://www.xxx.com/index.jsp/ 时，返回的IP地址始终是unknown，也并不是如上所示的127.0.0.1　或　192.168.1.110了，而我访问http://192.168.1.110:2046/index.jsp 时，则能返回客户端的真实IP地址，写了个方法去验证。原因出在了Squid上。squid.conf 的配制文件　forwarded_for 项默认是为on，如果 forwarded_for 设成了 off 　则：X-Forwarded-For: unknown

于是可得出获得客户端真实IP地址的方法二：

<wbr><wbr>1</wbr></wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>public<wbr><wbr>String<wbr><wbr>getIpAddr(HttpServletRequest <wbr><wbr>request) <wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>{
<wbr><wbr>2</wbr></wbr> <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>String<wbr><wbr>ip<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>=<wbr><wbr>request.getHeader(</wbr></wbr>"x-forwarded-for");
<wbr><wbr>3</wbr></wbr> <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>if(ip<wbr><wbr></wbr></wbr>==<wbr><wbr></wbr></wbr>null<wbr><wbr></wbr></wbr>||<wbr><wbr>ip.length()<wbr><wbr></wbr></wbr></wbr></wbr>==<wbr><wbr></wbr></wbr>0<wbr><wbr></wbr></wbr>||<wbr><wbr></wbr></wbr>"unknown".equalsIgnoreCase(ip))<wbr><wbr></wbr></wbr>{
<wbr><wbr>4</wbr></wbr> <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>ip<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>=<wbr><wbr>request.getHeader(</wbr></wbr>"Proxy-Client-IP");
<wbr><wbr>5</wbr></wbr> <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>}</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
<wbr><wbr>6</wbr></wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>if(ip<wbr><wbr></wbr></wbr>==<wbr><wbr></wbr></wbr>null<wbr><wbr></wbr></wbr>||<wbr><wbr>ip.length()<wbr><wbr></wbr></wbr></wbr></wbr>==<wbr><wbr></wbr></wbr>0<wbr><wbr></wbr></wbr>||<wbr><wbr></wbr></wbr>"unknown".equalsIgnoreCase(ip))<wbr><wbr></wbr></wbr>{
<wbr><wbr>7</wbr></wbr> <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>ip<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>=<wbr><wbr>request.getHeader(</wbr></wbr>"WL-Proxy-Client-IP");
<wbr><wbr>8</wbr></wbr> <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>}</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
<wbr><wbr>9</wbr></wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>if(ip<wbr><wbr></wbr></wbr>==<wbr><wbr></wbr></wbr>null<wbr><wbr></wbr></wbr>||<wbr><wbr>ip.length()<wbr><wbr></wbr></wbr></wbr></wbr>==<wbr><wbr></wbr></wbr>0<wbr><wbr></wbr></wbr>||<wbr><wbr></wbr></wbr>"unknown".equalsIgnoreCase(ip))<wbr><wbr></wbr></wbr>{
10 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>ip<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>=<wbr><wbr>request.getRemoteAddr();<br></wbr></wbr>11 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>}</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
12<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>return<wbr><wbr>ip;<br></wbr></wbr>13 <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>}</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

　　可是，如果通过了多级反向代理的话，X-Forwarded-For的值并不止一个，而是一串Ｉｐ值，究竟哪个才是真正的用户端的真实IP呢？

　　答案是取X-Forwarded-For中第一个非unknown的有效IP字符串。

　　如：
　　X-Forwarded-For：192.168.1.110, 192.168.1.120, 192.168.1.130, 192.168.1.100
　　用户真实IP为： 192.168.1.110