Appengine - Deployment of hidden folder

For anyone else coming here like me after trying to serve the challenge for letsencrypt in a static manner in Google App Engine and failing, the following did it for me: (one might be able to actually do it statically, but I didn't try it as I didn't want to spend more time trying out stuff and Ian apparently tried that and could not make it work [maybe the copy command done internally on Google App Engine ignores the directories that start with a dot] )

Taken from http://igorartamonov.com/2015/12/lets-encrypt-ssl-google-appengine/ credits go to Igor Artamonov.

Just build a servlet like:

public class LetsencryptServlet extends HttpServlet {

    public static final Map<String, String> challenges = new HashMap<String, String>();

    static {
        challenges.put("RzrvZ9gd7EH3i_TsJM-B0vdEMslD4oo_lwsagGskp6c",
                "RzrvZ9gd7EH3i_TsJM-B0vdEMslD4oo_lwsagGskp6c.ONrZa3UelibSWEX270nTUiRZKPFXw096nENWbMGw0-E");
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        if (!req.getRequestURI().startsWith("/.well-known/acme-challenge/")) {
            resp.sendError(404);
            return;
        }
        String id = req.getRequestURI().substring("/.well-known/acme-challenge/".length());
        if (!challenges.containsKey(id)) {
            resp.sendError(404);
            return;
        }
        resp.setContentType("text/plain");
        resp.getOutputStream().print(challenges.get(id));
    }
}

And add to web.xml somethine like:

<servlet>
    <servlet-name>letsencrypt</servlet-name>
    <servlet-class>...LetsencryptServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>letsencrypt</servlet-name>
    <url-pattern>/.well-known/acme-challenge/*</url-pattern>
</servlet-mapping>

Of course, be sure that the servlet class has the full classpath for your created Servlet.

That blog post also deals with the other steps necessary to generate and install the certificate.

Ian: Are you sure that you were deploying the servlet well? check the logs, make sure that you are testing the right version.. maybe you had a compilation issue..

Cheers

I ran into this problem trying to serve an assetlinks.json file. It would indeed appear that folders starting with a . are not accessible within the static context in App Engine. A more generic version of João Antunes workaround is as follows.

First, create the folder without the . at the start and place any required files inside it.

We then need to create a servlet that will respond with the correct data when a request to the hidden folder is received.

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;

/**
 * Created by Will Calderwood on 17/05/2017.
 * <p>
 * It would appear to not be possible to upload hidden folders to app engine. So when files need
 * to be served from a hidden folder the URL can be bounced through this servlet
 */
public class StaticFileServer extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // We'll remove the dots from the path
        String uri = req.getRequestURI().replace("/.", "/");

        // Do anything else that needs doing here
        if (uri.toLowerCase().contains(".json")) {
            resp.setContentType("application/json");
        }

        // Read and return the resource from the non-hidden folder
        try (InputStream in = getServletContext().getResourceAsStream(uri)) {
            if (in == null){
                resp.sendError(404);
                return;
            }
            byte[] buffer = new byte[8192];
            int count;
            while ((count = in.read(buffer)) > 0) {
                resp.getOutputStream().write(buffer, 0, count);
            }
        }
    }
}

Then add the following to your web.xml file to point the hidden folder at our servlet

<servlet>
    <servlet-name>StaticFileServer</servlet-name>
    <servlet-class>main.com.you.StaticFileServer</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>StaticFileServer</servlet-name>
    <url-pattern>/.well-known/*</url-pattern>
</servlet-mapping>