Determine whether a user is logged on and solve the problem of repeated User Logon

Solve the Problem of User Logon: (write a filter)

Public class check_user_loginfilter implements filter {

Protected filterconfig;

Public void Init (filterconfig arg0) throws servletexception {
// Todo auto-generated method stub
This. filterconfig = arg0;
}

Public void dofilter (servletrequest request, servletresponse response,
Filterchain chain) throws ioexception, servletexception {
// Todo auto-generated method stub
Httpservletrequest sr = (httpservletrequest) request;
Httpsession session = Sr. getsession (); // GET THE SESSION
Register User = (Register) Session. getattribute ("userinfo ");
Sessionlistener SL = new sessionlistener ();

 

// Determine whether the user is logged on. If not,
If (user = NULL | user. Equals ("")){

// Obtain the current URL of the token
String strurl = Sr. getrequesturl (). tostring ();
// Determine whether it is index. jsp or userlogin. Do
If (strurl. indexof ("/index. jsp") =-1 ){
If (strurl. indexof ("/userlogin. Do") =-1 ){
Servletcontext SC = filterconfig
. Getservletcontext ();
Requestdispatcher RD = SC
. Getrequestdispatcher ("/work/index. jsp ");
Try {
Rd. Forward (request, response); // forward to index. jsp for User Login
// Chain. dofilter (request, response );
Return;
} Catch (servletexception SX ){
Filterconfig. getservletcontext (). Log (
SX. getmessage ());
} Catch (ioexception iox ){
Filterconfig. getservletcontext (). Log (
Iox. getmessage ());
}
}
}
}
Chain. dofilter (request, response );

}

Public void destroy (){
// Todo auto-generated method stub
This. filterconfig = NULL;
}

}

<! -- Webxml judge User Logon -->

<Filter>
<Filter-Name> check_user_loginfilter </filter-Name>
<Filter-class>
Com. WP. App. util. check_user_loginfilter
</Filter-class>
</Filter>
<Filter-mapping>
<Filter-Name> check_user_loginfilter </filter-Name>
<URL-pattern> *. jsp </url-pattern>
</Filter-mapping>
<Filter-mapping>
<Filter-Name> check_user_loginfilter </filter-Name>
<URL-pattern> *. DO </url-pattern>
</Filter-mapping>
<Filter-mapping>
<Filter-Name> check_user_loginfilter </filter-Name>
<URL-pattern> *. html </url-pattern>
</Filter-mapping>

Solve the Problem of repeated User Logon: (configure listener implementation. If you log on repeatedly, t will be dropped from the previous user)

Public class sessionlistener implements httpsessionlistener {
Private Static java. util. hashtable husername = new hashtable ();
Public void sessioncreated (httpsessionevent SE ){
System. Out. println ("a new user session has been created --" + Se );
}

Public void sessiondestroyed (httpsessionevent SE ){
Husername. Remove (SE. getsession ());
System. Out. println ("delete user session --" + Se );
}

Public synchronized static Boolean islogined (httpsession session, string susername ){
Boolean flag = false;
If (husername. containskey (susername )){
Flag = true;
Httpsession vsession = (httpsession) husername. Get (susername );
Try {
Vsession. invalidate ();
System. Out. println ("user-" + susername + "| the session already exists-" + session );
System. Out. println ("Set-" + susername + "| session expired and removed ");
}
Catch (exception ex ){}
}
Else {
Flag = false;

}
Husername. Remove (susername );
Husername. Put (susername, session );
System. Out. println ("create user-" + susername + "| session-" + session );

Return flag;
}

Public synchronized static Boolean deleteusername (httpsession session, string susername)
{
System. Out. println ("delete user-" + susername + "| session-" + session );
Husername. Remove (susername); // delete a user
Return true;
}

Public synchronized static Boolean isonline (httpsession session, string susername ){
Boolean flag = false;
Httpsession vsession = NULL;
Try {
Vsession = (httpsession) husername. Get (susername );
} Catch (exception e ){

}
If (vsession! = NULL ){
If (session. GETID (). Equals (vsession. GETID ())){
Flag = true;
} Else {
Flag = false;
}
}
Return flag;

}
}

 

<! -- Webxml configuration listener -->
<Listener>
<Listener-class> com. Lihong. WP. Web. Action. loginaction. sessionlistener </listener-class>
</Listener>