思路:在服务器端生成一个唯一的随机标识串Token,同时在当前用户的Session域中保存这个Token。然后将Token发送到客户端的Form表单中,在Form表单中使用隐藏域来存储这个Token,表单提交的时候连同这个Token一起提交到服务器端,然后在服务器端判断客户端提交上来的Token与服务器端生成的Token是否一致,如果不一致,那就是重复提交了,此时服务器端就可以不处理重复提交的表单。如果相同则处理表单提交,处理完后清除当前用户的Session域中存储的标识串。
服务器程序将拒绝处理用户提交的表单请求:
1,存储Session域中的Token与表单提交的Token不同。
2,当前用户的Session中不存在Token。
3,用户提交的表单数据中没有Token。
/**
* 防重复提交工具类
*/
public class TokenUtil {
private static String REPEAT_SUBMIT_TOKEN = "REPEAT_SUBMIT_TOKEN";
private static TokenUtil instance = new TokenUtil();
private TokenUtil() {
}
public static TokenUtil getInstance() {
return instance;
}
public static boolean isTokenValid(HttpServletRequest request) {
return instance.isTokenValid(request, true);
}
public static boolean isTokenValid(HttpServletRequest request, boolean reset) {
HttpSession session = request.getSession(false);
if (session == null) {
return false;
}
String saved = (String) session.getAttribute(REPEAT_SUBMIT_TOKEN);
if (saved == null) {
return false;
}
if (reset) {
instance.resetToken(request);
}
String token = request.getParameter(REPEAT_SUBMIT_TOKEN);
if (token == null) {
return false;
}
return saved.equals(token);
}
public static void resetToken(HttpServletRequest request) {
HttpSession session = request.getSession(false);
if (session == null) {
return;
}
session.removeAttribute(REPEAT_SUBMIT_TOKEN);
}
public static void saveToken(HttpServletRequest request) {
HttpSession session = request.getSession();
String token = instance.generateToken(request);
if (token != null)
session.setAttribute(REPEAT_SUBMIT_TOKEN, token);
}
public static void saveToken(HttpServletRequest request, ResponseJSON responseJSON) {
HttpSession session = request.getSession();
String token = instance.generateToken(request);
if (token != null) {
session.setAttribute(REPEAT_SUBMIT_TOKEN, token);
}
if (responseJSON != null) {
responseJSON.setRepeatSubmitToken(token);
}
}
private String generateToken(HttpServletRequest request) {
HttpSession session = request.getSession();
return generateToken(session.getId());
}
private String generateToken(String id) {
try {
long current = System.currentTimeMillis();
current += new java.util.Random().nextInt(100);
byte[] now = new Long(current).toString().getBytes();
MessageDigest md = MessageDigest.getInstance("MD5");
md.update(id.getBytes());
md.update(now);
return toHex(md.digest());
} catch (NoSuchAlgorithmException e) {
}
return null;
}
private 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] & 0xF0) >> 4, 16));
sb.append(Character.forDigit(buffer[i] & 0xF, 16));
}
return sb.toString();
}
}
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