一个简单的签名方法

public class SignUtil {
    private static String privateKey = "xxx" ;
    
    public static void main(String[] args)  throws Exception {
        Map<String,String> data = new HashMap<String,String>();
        //用户名
        String username = "HelloKittyNMB";
        //访问时间
        String time = String.valueOf(System.currentTimeMillis());
        data.put("username", username);
        data.put("time", time);
        String sign = getSign(data);
    }
    
    /**
     * 获取用户接口数据的签名
     * 
     * @param data
     * @return
     * @throws NoSuchAlgorithmException
     * @throws UnsupportedEncodingException
     */
    public static String getSign(Map<String ,String> data) throws NoSuchAlgorithmException, UnsupportedEncodingException{
        String[] keys=new String[data.size()];
        int i=0;
        for(Map.Entry<String, String> entry:data.entrySet()){
            keys[i]=entry.getKey();
            i++;
        }
        Arrays.sort(keys);
        
        StringBuffer sb=new StringBuffer();
        for(String key :keys){
            sb.append(key);
            sb.append("=");
            sb.append(data.get(key));
            sb.append("&");
        }
        sb.append(privateKey);
        
        byte[] b=MessageDigest.getInstance("MD5").digest(sb.toString().getBytes("UTF-8"));//和教育用户接口为UTF-8编码
        sb=new StringBuffer();
        for(int j : b){
            j=j & 0xff;
            if(j<16)sb.append("0");
            sb.append(Integer.toHexString(j));
        }
        return sb.toString();
    }
    
}