@WebFilter exclude url-pattern

Question

I use a filter to check URL patterns for the logged in user.

But I have many URL patterns I need to filter.

{ "/table/*", "/user/*", "/contact/*", "/run/*", "/conf/*", ..., ..., ...}

It's becoming unmaintainable. It will be simpler just to exclude:

{ "/", "/login", "/logout", "/register" }

How can I achieve this?

@WebFilter(urlPatterns = { "/table/*","/user/*", "/contact/*","/run/*","/conf/*"})
public class SessionTimeoutRedirect implements Filter {

    protected final Logger logger = LoggerFactory.getLogger("SessionFilter");

    @Override
    public void doFilter(ServletRequest req, ServletResponse res,
            FilterChain chain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) res;
        if (request.getSession().getAttribute("Id") != null) {
            chain.doFilter(req, res);
        } else {
            logger.debug("session is null:"+request.getRequestURL());                    
            response.sendRedirect(request.getContextPath()+"/login");
        }
    }

    @Override
    public void init(FilterConfig arg0) throws ServletException {

    }

    @Override
    public void destroy() {

    }

}

Answer 1

The servlet API doesn't support an "exclude" URL pattern.

Your best bet is to just map on /* and compare the HttpServletRequest#getRequestURI() against the set of allowed paths.

@WebFilter("/*")
public class LoginFilter implements Filter {

    private static final Set<String> ALLOWED_PATHS = Collections.unmodifiableSet(new HashSet<>(
        Arrays.asList("", "/login", "/logout", "/register")));

    @Override
    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) res;
        HttpSession session = request.getSession(false);
        String path = request.getRequestURI().substring(request.getContextPath().length()).replaceAll("[/]+$", ""); 

        boolean loggedIn = (session != null && session.getAttribute("Id") != null);
        boolean allowedPath = ALLOWED_PATHS.contains(path);

        if (loggedIn || allowedPath) {
            chain.doFilter(req, res);
        }
        else {
            response.sendRedirect(request.getContextPath() + "/login");
        }
    }

    // ...
}

Answer 2

You can use initParam to have some excluded patterns and implement your logic. This is basically the same as BalusC's answer except by using initParam it can be written in the web.xml if you want/need to.

Below I am ignoring some binary (jpeg jpg png pdf) extensions:

@WebFilter(urlPatterns = { "/*" },
    initParams = { @WebInitParam(name = "excludedExt", value = "jpeg jpg png pdf") }
)
public class GzipFilter implements Filter {

    private static final Set<String> excluded;

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        String excludedString = filterConfig.getInitParameter("excludedExt");
        if (excludedString != null) {
            excluded = Collections.unmodifiableSet(
                new HashSet<>(Arrays.asList(excludedString.split(" ", 0))));
        } else {
            excluded = Collections.<String>emptySet();
        }
    }

    boolean isExcluded(HttpServletRequest request) {
        String path = request.getRequestURI();
        String extension = path.substring(path.indexOf('.', path.lastIndexOf('/')) + 1).toLowerCase();
        return excluded.contains(extension);
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        System.out.print("GzipFilter");
        HttpServletRequest httpRequest = (HttpServletRequest) request;
        HttpServletResponse httpResponse = (HttpServletResponse) response;
        if (isExcluded(httpRequest)) {
            chain.doFilter(request, response);
            return;
        }

        // Do your stuff here
    }
}