[java] How to redirect in a servlet filter?

I'm trying to find a method to redirect my request from a filter to the login page but I don't know how to redirect from servlet. I've searched but what I find is sendRedirect() method. I can't find this method on my response object in the filter. What's the cause? How can I solve this?

If you also want to keep hash and get parameter, you can do something like this (fill redirectMap at filter init):

String uri = request.getRequestURI();

String[] uriParts = uri.split("[#?]");
String path = uriParts[0];
String rest = uri.substring(uriParts[0].length());

if(redirectMap.containsKey(path)) {
    response.sendRedirect(redirectMap.get(path) + rest);
} else {
    chain.doFilter(request, response);
}

I'm trying to find a method to redirect my request from filter to login page

Don't

You just invoke

chain.doFilter(request, response);

from filter and the normal flow will go ahead.

I don't know how to redirect from servlet

You can use

response.sendRedirect(url);

to redirect from servlet

Your response object is declared as a ServletResponse. To use the sendRedirect() method, you have to cast it to HttpServletResponse. This is an extended interface that adds methods related to the HTTP protocol.

Try and check of your ServletResponse response is an instanceof HttpServletResponse like so:

if (response instanceof HttpServletResponse) {
    response.sendRedirect(....);
}