package com.yc.utils;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;

/**
 * 令牌生成类
 * */
public class TokenUtil {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		System.out.print(generateToken(null));

	}

public static String generateToken(HttpServletRequest request) { 
    HttpSession session = request.getSession(); 
    try { 
        byte id[] = session.getId().getBytes(); 
        byte now[] = 
            new Long(System.currentTimeMillis()).toString().getBytes(); 
        MessageDigest md = MessageDigest.getInstance("MD5"); 
        md.update(id); 
        md.update(now); 
        String token=bytesToHexString(md.digest());
        session.setAttribute("_token",token );
        return token; 
    } catch (IllegalStateException e) { 
        return (null); 
    } catch (NoSuchAlgorithmException e) { 
        return (null); 
    } 
} 
public static String bytesToHexString(byte[] src){
	   StringBuilder stringBuilder = new StringBuilder("");
	   if (src == null || src.length <= 0) {
	       return null;
	   }
	   for (int i = 0; i < src.length; i++) {
	       int v = src[i] & 0xFF;
	       String hv = Integer.toHexString(v);
	       if (hv.length() < 2) {
	           stringBuilder.append(0);

	       }
	       stringBuilder.append(hv);

	   }
	   return stringBuilder.toString();
	    }
}