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();
}
}