Java获取客户端IP[通俗易懂]

大家好，又见面了，我是全栈君。

转载地址：Java获取客户端IP
这里虽然是转载的博文，在看博文之前先说明一下，如果你使用的是公司的内网访问，那么对外的出口可能只有一个或者几个，那么客户端的IP就有可能两个人获取的同样的IP！
在开发工作中,我们常常需要获取客户端的IP。一般获取客户端的IP地址的方法是:request.getRemoteAddr();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。

原因:由于在客户端和服务之间增加了中间代理,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。

现在图示代理上网和IP的关系：

第二种情况：通过代理服务器如:Nginx,Squid等一层代理或多层代理上网，如下图:
这里写图片描述
需要注意的是X-Forwarded-For和X-Real-IP都不是http的正式协议头，而是squid等反向代理软件最早引入的，之所以resin能拿到，是因为NGINX里一般缺省都会这么配置转发的http请求：

location / {

         proxy_pass       http://yourdomain.com;

         proxy_set_header   Host             $host;

         proxy_set_header   X-Real-IP        $remote_addr;

         proxy_set_header   X-Forwarded-For  $proxy_add_x_forwarded_for;

         }

从X-Forwarded-For的定义来看，ips[0]才是原始客户端ip，如果这个都不是，那拿第二个就更不靠谱了，我们平时检验的时候，可能是直接在内网挂代理去访问的，跟外面网友访问经过的网络路径不一样，后面不停添加的是经过的每一层代理ip才对,下面举例说明;

request.getRemoteAddr() 192.168.239.196

request.getHeader(“X-Forwarded-For”) 58.63.227.162, 192.168.237.178, 192.168.238.218

request.getHeader(“X-Real-IP”) 192.168.238.218

所以访问的流程应该是这样，客户端58.63.227.162发出请求，经过192.168.237.178, 192.168.238.218两层转发，到了192.168.239.196这台NGINX上，NGINX就把X-Real-IP头设成了自己看到的remote_addr，也就是直接发给到他的192.168.238.218，这时候resin收到这个包，对resin来说直接发给他的remote_addr就是NGINX的ip，也就是192.168.239.196，那么resin里面的request.getRemoteAddr()就是192.168.239.196，那么在resin里拿最原始的ip逻辑（也就是拿能够知道的最外层的ip）应该是这样：

        如果XFF不为空，拿XFF的左边第一个

        如果XFF为空，拿XRI

        如果XRI为空，只能拿request.getRemoteAddr()，也就是只能拿到最直接发给他的机器ip了，

其他都不可考究,参考代码如下：

第一种代码：

/** * 从Request对象中获得客户端IP，处理了HTTP代理服务器和Nginx的反向代理截取了ip * @param request * @return ip */
    public static String getLocalIp(HttpServletRequest request) {
        String remoteAddr = request.getRemoteAddr();
        String forwarded = request.getHeader("X-Forwarded-For");
        String realIp = request.getHeader("X-Real-IP");

        String ip = null;
        if (realIp == null) {
            if (forwarded == null) {
                ip = remoteAddr;
            } else {
                ip = remoteAddr + "/" + forwarded.split(",")[0];
            }
        } else {
            if (realIp.equals(forwarded)) {
                ip = realIp;
            } else {
                if(forwarded != null){
                    forwarded = forwarded.split(",")[0];
                }
                ip = realIp + "/" + forwarded;
            }
        }
        return ip;
    }

第二种代码:

public static String getIp(HttpServletRequest request) {
        String remoteAddr = request.getRemoteAddr();
        String forwarded = request.getHeader("X-Forwarded-For");
        String realIp = request.getHeader("X-Real-IP");

        String ip = null;
        if (realIp == null) {
            if (forwarded == null) {
                ip = remoteAddr;
            } else {
                ip = remoteAddr + "/" + forwarded;
            }
        } else {
            if (realIp.equals(forwarded)) {
                ip = realIp;
            } else {
                ip = realIp + "/" + forwarded.replaceAll(", " + realIp, "");
            }
        }
        return ip;
    }

第三种代码:

public static String getIp2(HttpServletRequest request) {
           String ip = request.getHeader("X-Forwarded-For");
           if(StringUtils.isNotEmpty(ip) && !"unKnown".equalsIgnoreCase(ip)){
               //多次反向代理后会有多个ip值，第一个ip才是真实ip
               int index = ip.indexOf(",");
               if(index != -1){
                   return ip.substring(0,index);
               }else{
                   return ip;
               }
           }
           ip = request.getHeader("X-Real-IP");
           if(StringUtils.isNotEmpty(ip) && !"unKnown".equalsIgnoreCase(ip)){
               return ip;
           }
           return request.getRemoteAddr();
       }

第三种是最合适的，最清晰理解的！

附两个方法：也是从其他地方看到的，记录下来，方便以后学习！

/** * 通过HttpServletRequest返回IP地址 * @param request HttpServletRequest * @return ip String * @throws Exception */
public String getIpAddr(HttpServletRequest request) throws Exception {
    String ip = request.getHeader("x-forwarded-for");
    if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
        ip = request.getHeader("Proxy-Client-IP");
    }
    if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
        ip = request.getHeader("WL-Proxy-Client-IP");
    }
    if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
        ip = request.getHeader("HTTP_CLIENT_IP");
    }
    if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
        ip = request.getHeader("HTTP_X_FORWARDED_FOR");
    }
    if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
        ip = request.getRemoteAddr();
    }
    return ip;
}



 /** * 通过IP地址获取MAC地址 * @param ip String,127.0.0.1格式 * @return mac String * @throws Exception */
public String getMACAddress(String ip) throws Exception {
    String line = "";
    String macAddress = "";
    final String MAC_ADDRESS_PREFIX = "MAC Address = ";
    final String LOOPBACK_ADDRESS = "127.0.0.1";
    //如果为127.0.0.1,则获取本地MAC地址。
    if (LOOPBACK_ADDRESS.equals(ip)) {
        InetAddress inetAddress = InetAddress.getLocalHost();
        //貌似此方法需要JDK1.6。
        byte[] mac = NetworkInterface.getByInetAddress(inetAddress).getHardwareAddress();
        //下面代码是把mac地址拼装成String
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < mac.length; i++) {
            if (i != 0) {
                sb.append("-");
            }
            //mac[i] & 0xFF 是为了把byte转化为正整数
            String s = Integer.toHexString(mac[i] & 0xFF);
            sb.append(s.length() == 1 ? 0 + s : s);
        }
        //把字符串所有小写字母改为大写成为正规的mac地址并返回
        macAddress = sb.toString().trim().toUpperCase();
        return macAddress;
    }
    //获取非本地IP的MAC地址
    try {
        Process p = Runtime.getRuntime().exec("nbtstat -A " + ip);
        InputStreamReader isr = new InputStreamReader(p.getInputStream());
        BufferedReader br = new BufferedReader(isr);
        while ((line = br.readLine()) != null) {
            if (line != null) {
                int index = line.indexOf(MAC_ADDRESS_PREFIX);
                if (index != -1) {
                    macAddress = line.substring(index + MAC_ADDRESS_PREFIX.length()).trim().toUpperCase();
                }
            }
        }
        br.close();
    } catch (IOException e) {
        e.printStackTrace(System.out);
    }
    return macAddress;
}