How to restrict the no of user in the struts web applcation?

Question

I have a very minimal struts app I wrote some years ago. I want to upgrade it from 2.3 to 2.5. I'm wondering what requirements would allow the use of the essential dependencies jar. I am using only jstl tags, no struts tags. And my app is pretty simple.

Answer 1

1. Place the SessionID in the DB column against every session created by the user.
2. This will provide count of the sessions currently active for the current user(s).
3. Use a LoginServlet to check on the number of users having the active session (query the User_session table (from the DB) and check against the count.)

But in summary I agree this is a very open question and require more thoughts and inputs before answered precisely. Let me know if it serves the purpose.

Answer 2

it is intended in a "container" way, this should go:

@WebFilter("/*")
public class RequestFilter implements Filter
{
    private static final int THRESHOLD = 5;
    private static Map<String, AtomicInteger> accessMap = new HashMap<String, AtomicInteger>();

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException
    {
        HttpServletRequest request = (HttpServletRequest) servletRequest;

        AtomicInteger counter = accessMap.get(request.getRequestURI());
        if(counter == null) counter = new AtomicInteger();

        if(counter.incrementAndGet() < THRESHOLD)
        {
            filterChain.doFilter(servletRequest, servletResponse);
        }

        counter.decrementAndGet();
    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException
    {
        // nothing to do
    }

    @Override
    public void destroy()
    {
        // nothing to do
    }