获得客户端的真实IP

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("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(); 
        } 
        //防止多级代理时返回过个ip。 
        if(ip != null && ip.indexof(",") != -1){ 
            ip= ip.substring(0,ip.indexof(",")); 
        } 
        return ip; 
    } 
}