java-TokenProcessor令牌校验工具类

TokenProcessor令牌校验工具类

 public class TokenProcessor {

    private long privious;// 上次生成表单标识号得时间值
    private static TokenProcessor instance = new TokenProcessor();
    public static String FORM_TOKEN_KEY = "FORM_TOKEN_KEY";

    private TokenProcessor() {
    }

    public static TokenProcessor getInstance() {
        return instance;
    }

    /**
     * 验证请求中得标识号是否有效，如果请求中的表单标识与当前用户session中的相同，返回结果true=
     */
    public synchronized boolean isTokenValid(HttpServletRequest request) {
        // 为避免session对象不存在时候创建Session对象
        HttpSession session = request.getSession(false);
        if (session == null) {
            return false;
        }
        String saved = (String) session.getAttribute(FORM_TOKEN_KEY);
        if (saved == null) {
            return false;
        }
        String token = (String) request.getParameter(FORM_TOKEN_KEY);
        if (token == null) {
            return false;
        }
        return saved.equals(token);
    }
    
    /**
     * 验证请求中得标识号是否有效，如果请求中的表单标识与当前用户session中的相同，返回结果true=
     */
    public synchronized boolean isTokenValid(HttpServletRequest request,String token) {
        // 未避免session对象不存在时候创建Session对象
        HttpSession session = request.getSession(false);
        if (session == null) {
            return false;
        }
        String saved = (String) session.getAttribute(FORM_TOKEN_KEY);
        if (saved == null) {
            return false;
        }
        if (token == null) {
            return false;
        }
        return saved.equals(token);
    }
    
    
    /**
     * 清除存储在当前用户session中的表单标识号
     */
    public synchronized void reset(HttpServletRequest request) {
        HttpSession session = request.getSession(false);
        if (session == null) {
            return;
        }
        session.removeAttribute(FORM_TOKEN_KEY);
    }

    /**
     * 产生表单标识号并将之保存在当前用户得session中
     */
    public synchronized void saveToken(HttpServletRequest request) {
        HttpSession session = request.getSession();
        try {
            byte id[] = session.getId().getBytes();
            long current = System.currentTimeMillis();
            if (current == privious) {
                current++;
            }
            privious = current;
            byte now[] = String.valueOf(current).getBytes();
            MessageDigest md = MessageDigest.getInstance("MD5");
            md.update(id);
            md.update(now);
            String token = toHex(md.digest());
            session.setAttribute(FORM_TOKEN_KEY, token);
        } catch (NoSuchAlgorithmException e) {
        }
    }

    /**
     * 将一个字节数转换成十六进制得字符串
     */
    public String toHex(byte buffer[]) {
        StringBuffer sb = new StringBuffer(buffer.length * 2);
        for (int i = 0; i < buffer.length; i++) {
            sb.append(Character.forDigit((buffer[i] & 0x60) >> 4, 16));
            sb.append(Character.forDigit(buffer[i] & 0x0f, 16));
        }
        return sb.toString();
    }
}