java中获取真是ip地址方法

package com.rapido.utils; 
  
import javax.servlet.http.HttpServletRequest; 
  
/** 
 * 自定义访问对象工具类 
 * 
 * 获取对象的IP地址等信息 
 * @author X-rapido 
 * 
 */
public class CusAccessObjectUtil { 
  
  /** 
   * 获取用户真实IP地址，不使用request.getRemoteAddr();的原因是有可能用户使用了代理软件方式避免真实IP地址, 
   * 
   * 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 
   * 
   * @param request 
   * @return 
   */
  public static String getIpAddress(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.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; 
  } 
    
}