package com.atlassian.plugin.servlet;
   
   import com.atlassian.plugin.servlet.util.ServletContextServletModuleManagerAccessor;
   import org.slf4j.Logger;
   import org.slf4j.LoggerFactory;
   
   import javax.servlet.ServletConfig;
   import javax.servlet.ServletException;
   import javax.servlet.UnavailableException;
  import javax.servlet.http.HttpServlet;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  import java.io.IOException;
  
  /**
   * Applications need to create a concrete subclass of this for use in their webapp.  This servlets responsiblity
   * is to retrieve the servlet to be used to serve the request from the {@link ServletModuleManager}.  If no servlet
   * can be found to serve the request, a 404 should be sent back to the client.
   */
  public class ServletModuleContainerServlet extends HttpServlet {
      private static final Logger log = LoggerFactory.getLogger(ServletModuleContainerServlet.class);
      private ServletConfig servletConfig;
  
      public void init(ServletConfig servletConfig) throws ServletException {
          super.init(servletConfig);
          this.servletConfig = servletConfig;
      }
  
      protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          if (getServletModuleManager() == null) {
              log.error("Could not get ServletModuleManager?");
              response.sendError(500, "Could not get ServletModuleManager.");
              return;
          }
  
          HttpServlet servlet = getServletModuleManager().getServlet(getPathInfo(request), servletConfig);
  
          if (servlet == null) {
              log.debug("No servlet found for: " + getRequestURI(request));
              response.sendError(404, "Could not find servlet for: " + getRequestURI(request));
              return;
          }
  
          try {
              servlet.service(request, response);
          } catch (UnavailableException e) // prevent this servlet from unloading itself (PLUG-79)
          {
              log.error(e.getMessage(), e);
              response.sendError(500, e.getMessage());
          } catch (ServletException e) {
              log.error(e.getMessage(), e);
              response.sendError(500, e.getMessage());
          }
      }
  
      /**
       * @return the DefaultServletModuleManager from your container framework.  Uses the {@link com.atlassian.plugin.servlet.util.ServletContextServletModuleManagerAccessor}
       * by default.
       */
      protected ServletModuleManager getServletModuleManager() {
          return ServletContextServletModuleManagerAccessor.getServletModuleManager(getServletContext());
      }
  
      private String getPathInfo(HttpServletRequest request) {
          String pathInfo = (String) request.getAttribute(RequestAttributes.PATH_INFO);
          if (pathInfo == null) {
              pathInfo = request.getPathInfo();
          }
          return pathInfo;
      }
  
      private String getRequestURI(HttpServletRequest request) {
          String requestURI = (String) request.getAttribute(RequestAttributes.REQUEST_URI);
          if (requestURI == null) {
              requestURI = request.getRequestURI();
          }
          return requestURI;
      }
  
      private static class RequestAttributes {
          static final String PATH_INFO = "javax.servlet.include.path_info";
          static final String REQUEST_URI = "javax.servlet.include.request_uri";
      }
  }