从request中获取IP

import javax.servlet.http.HttpServletRequest;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class IpUtil {

	private static final Logger logger = LoggerFactory.getLogger(IpUtil.class);
	
	public static String getIp(HttpServletRequest request){
		/**
		 * 获取客户端ip，客户端可能经过代理，也可能没经过代理
		 */
        String ip = request.getHeader("x-forwarded-for"); 
        logger.debug("x-forwarded-for ip: " + ip);
        if (ip != null && ip.length() != 0 && !"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
            if( ip.indexOf(",")!=-1 ){
                ip = ip.split(",")[0];
            }
        }  
        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {  
            ip = request.getHeader("Proxy-Client-IP");  
            logger.debug("Proxy-Client-IP ip: " + ip);
        }  
        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {  
            ip = request.getHeader("WL-Proxy-Client-IP");  
            logger.debug("WL-Proxy-Client-IP ip: " + ip);
        }  
        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {  
            ip = request.getHeader("HTTP_CLIENT_IP");  
            logger.debug("HTTP_CLIENT_IP ip: " + ip);
        }  
        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {  
            ip = request.getHeader("HTTP_X_FORWARDED_FOR");  
            logger.debug("HTTP_X_FORWARDED_FOR ip: " + ip);
        }  
        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {  
            ip = request.getHeader("X-Real-IP");  
            logger.debug("X-Real-IP ip: " + ip);
        }  
        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {  
            ip = request.getRemoteAddr();  
            logger.debug("getRemoteAddr ip: " + ip);
        } 
        
        logger.debug("----获取客户端的ip: " + ip);
        //如果没取到ip，返回""
        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {  
            ip = "";
        } 
        
        return ip;
	}
}