クライアントの実際の IP を取得する

public class IPUtil {
public static String getIpAddr(HttpServletRequest request) {
String ip = request.getHeader("X-Real-IP"); 
if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
ip = request.getHeader("x-forwarded-for"); 
}
if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
ip = request.getHeader("プロキシクライアント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(); 
}
// 多層プロキシが ip を返すのを防ぎます。 "、")); 
}
IPを返します。 
}
}