How can I get the request URL from a Java Filter?

84
votes

I am trying to write a filter that can retrieve the request URL, but I'm not sure how to do so.

Here is what I have so far:

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;

public class MyFilter implements Filter {
    public void init(FilterConfig config) throws ServletException { }

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException {
        chain.doFilter(request, response);

        String url = ((HttpServletRequest) request).getPathTranslated();
        System.out.println("Url: " + url);
    }

    public void destroy() { }
}

When I hit a page on my server, the only output I see is "Url: null".

What is the correct way to get the requested URL from a given ServletRequest object in a Filter?

4
javaurlservlet-filters

4 Answers

186
votes

Is this what you're looking for?

if (request instanceof HttpServletRequest) {
 String url = ((HttpServletRequest)request).getRequestURL().toString();
 String queryString = ((HttpServletRequest)request).getQueryString();
}

To Reconstruct:

System.out.println(url + "?" + queryString);

Info on HttpServletRequest.getRequestURL() and HttpServletRequest.getQueryString().

4
votes

Building on another answer on this page,

public static String getCurrentUrlFromRequest(ServletRequest request)
{
   if (! (request instanceof HttpServletRequest))
       return null;

   return getCurrentUrlFromRequest((HttpServletRequest)request);
}

public static String getCurrentUrlFromRequest(HttpServletRequest request)
{
    StringBuffer requestURL = request.getRequestURL();
    String queryString = request.getQueryString();

    if (queryString == null)
        return requestURL.toString();

    return requestURL.append('?').append(queryString).toString();
}
1
votes

If you use Spring, you can use OncePerRequestFilter or others.

import org.springframework.web.filter.OncePerRequestFilter;
import org.springframework.stereotype.Component;

@Component
public class MyFilter extends OncePerRequestFilter {
    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
         String url = request.getRequestURL();
         filterChain.doFilter(request, response);
    }

}
0
votes
request.getRequestURL();