AttributesDump.java

package jetty;

import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Collections;
import java.util.Enumeration;
import java.util.List;
import java.util.function.Function;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.servlet.ServletContextHandler;

public class AttributesDump
{
    public static void main(String[] args) throws Exception
    {
        Server server = new Server(9090);

        ServletContextHandler context = new ServletContextHandler();
        context.setContextPath("/");
        context.addServlet(AttrDumpServlet.class, "/dump");
        context.addEventListener(new AttrDumpListener());

        server.setHandler(context);
        server.start();

        try
        {
            dumpAttrs("server.attrs (post-start)", server.getAttributeNames(), (name) -> server.getAttribute(name));

            HttpURLConnection http = (HttpURLConnection) new URL("http://localhost:9090/dump").openConnection();
            System.out.println("Http.responseCode = " + http.getResponseCode());
        }
        finally
        {
            server.stop();
        }
    }

    private static void dumpAttrs(String scope, Enumeration<String> enNames, Function<String, Object> funcGetValue)
    {
        List<String> names = Collections.list(enNames);
        System.out.printf("[%s] count = %,d%n", scope, names.size());
        names.stream().forEach((name) -> {
            Object val = funcGetValue.apply(name);
            if (val == null)
                System.out.printf("[%s] [%s] = <null>%n", scope, name);
            else
                System.out.printf("[%s] [%s] = (%s)%s%n", scope, name, val.getClass().getName(), val.toString());
        });
    }

    public static class AttrDumpListener implements ServletContextListener
    {
        @Override
        public void contextInitialized(ServletContextEvent sce)
        {
            ServletContext context = sce.getServletContext();
            dumpAttrs("context.attrs (post-initialized)", context.getAttributeNames(), (name) -> context.getAttribute(name));
        }

        @Override
        public void contextDestroyed(ServletContextEvent sce)
        {
        }
    }

    public static class AttrDumpServlet extends HttpServlet
    {
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException
        {
            ServletContext context = req.getServletContext();
            dumpAttrs("context.attrs (doGet)", context.getAttributeNames(), (name) -> context.getAttribute(name));
            dumpAttrs("request.attrs (doGet)", req.getAttributeNames(), (name) -> req.getAttribute(name));
            resp.setStatus(200);
        }
    }
}