java 获取请求客户端的真实IP地址

用request.getRemoteAddr() 

方法获取的IP地址是：127.0.0.1　或　192.168.0.66，而并非客户端的真实ＩＰ。 

通过代理之后，因为在客户端和服务之间增长了中间层，所以服务器没法直接拿到客户端的IP，服务器端应用也没法直接经过转发请求的地址返回给客户端。可是在转发请求的HTTP头信息中，增长了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。

 public String getIpAddr(HttpServletRequest request) {      
       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.getRemoteAddr();      
      }      
     return ip;      
}

像移动网关同样，iisforward这个ISAPI过滤器也会对request对象进行再包装，附加一些WLS要用的头信息。这种状况下，直接用request.getRemoteAddr()是没法取到真正的客户IP的。

实际的iisforward附加头以下：

WL-Proxy-Client-IP=215.4.1.29
Proxy-Client-IP=215.4.1.29
X-Forwarded-For=215.4.1.29
WL-Proxy-Client-Keysize=
WL-Proxy-Client-Secretkeysize=
X-WebLogic-Request-ClusterInfo=true
X-WebLogic-KeepAliveSecs=30
X-WebLogic-Force-JVMID=-527489098
WL-Proxy-SSL=false

综上，正确做法以下：代码

public static String getIpAddr(HttpServletRequest request) {
     String ipAddress = null;
     //ipAddress = request.getRemoteAddr();
     ipAddress = request.getHeader("x-forwarded-for");
     if(ipAddress == null || ipAddress.length() == 0 || "unknown".equalsIgnoreCase(ipAddress)) {
      ipAddress = request.getHeader("Proxy-Client-IP");
     }
     if(ipAddress == null || ipAddress.length() == 0 || "unknown".equalsIgnoreCase(ipAddress)) {
         ipAddress = request.getHeader("WL-Proxy-Client-IP");
     }
     if(ipAddress == null || ipAddress.length() == 0 || "unknown".equalsIgnoreCase(ipAddress)) {
      ipAddress = request.getRemoteAddr();
      if(ipAddress.equals("127.0.0.1")){
       //根据网卡取本机配置的IP
       InetAddress inet=null;
    try {
     inet = InetAddress.getLocalHost();
    } catch (UnknownHostException e) {
     e.printStackTrace();
    }
    ipAddress= inet.getHostAddress();
      }
        
     }

     //对于经过多个代理的状况，第一个IP为客户端真实IP,多个IP按照','分割
     if(ipAddress!=null && ipAddress.length()>15){ //"***.***.***.***".length() = 15
         if(ipAddress.indexOf(",")>0){
             ipAddress = ipAddress.substring(0,ipAddress.indexOf(","));
         }
     }
     return ipAddress;
}