Solution to repeated submission of JSP refresh Page forms

Use sessionID and timestamp as the identifier. The key code is as follows:

Copy codeThe Code is as follows:
Public class SswpdjAction extends BaseAction {

Public String execute (){
/** Business Code **/
................
// Set the identifier
This. setSessionToken ();
// Go To The add page
Return "toAdd ";
}
　　
Public String reSave (){
If (this. token! = Null & this. token. equals (this. getSessionToken ())){
/** Set a new ID **/
This. setSessionToken ();
　　　　　　
/** Business Code **/
..............
Return "toAdd ";
} Else {
PrintWriter out = null;
Try {
HttpServletResponse. setContentType ("text/html; charset = UTF-8 ");
Out = httpServletResponse. getWriter ();
Out. println ("<script> alert ('refresh the submission form! '); </Script> ");
Out. flush ();
　　　　　　　　
} Catch (IOException e ){
E. printStackTrace ();
} Finally {
If (out! = Null ){
Out. close ();
}
}
}
Return null;
}
}

Public class BaseAction extends ActionSupport {

/** Jsp page ID **/
Protected String token;

Public String getToken (){
Return token;
}

Public void setToken (String token ){
This. token = token;
}

Public String getSessionToken (){
If (null! = HttpSession. getAttribute ("Token ")){
Return httpSession. getAttribute ("Token ");
} Else {
Return null;
}
}

/** ID generation **/
Public void setSessionToken (){
String flag = useMd5 (httpSession. getId () + System. currentTimeMillis ());
HttpSession. setAttribute ("Token", flag );
HttpServletRequest. setAttribute ("SessionToken", flag );
}

/** MD5 encryption **/
Private String useMd5 (String str ){
Byte [] bs = str. getBytes ();
String result = null;
Try {
MessageDigest md5 = MessageDigest. getInstance ("MD5 ");
Md5.update (bs );
Result = md5.digest (). toString ();
} Catch (NoSuchAlgorithmException e ){
E. printStackTrace ();
} Finally {

}
Return result;
}
}

The following figure shows the hidden fields of the JSP page settings:

Copy codeThe Code is as follows:
<Form>
<Input type = "hidden" name = "token" value = "$ {SessionToken}"/>
</Form>