# AbstractModulesHandler.java

    /*
    ** Module   : AbstractModulesHandler.java
    ** Abstract : Delivers requested resources by loading them from the classpath
    **
    ** Copyright (c) 2017, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- ------------------------------Description----------------------------------
    ** 001 SBI 20170720 Generalized DojoToolkitHandler to be used to deliver js zipped modules.
    */
    /*
    ** This program is free software: you can redistribute it and/or modify
    ** it under the terms of the GNU Affero General Public License as
    ** published by the Free Software Foundation, either version 3 of the
    ** License, or (at your option) any later version.
    **
    ** This program is distributed in the hope that it will be useful,
    ** but WITHOUT ANY WARRANTY; without even the implied warranty of
    ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    ** GNU Affero General Public License for more details.
    **
    ** You may find a copy of the GNU Affero GPL version 3 at the following
    ** location: https://www.gnu.org/licenses/agpl-3.0.en.html
    **
    ** Additional terms under GNU Affero GPL version 3 section 7:
    **
    **   Under Section 7 of the GNU Affero GPL version 3, the following additional
    **   terms apply to the works covered under the License.  These additional terms
    **   are non-permissive additional terms allowed under Section 7 of the GNU
    **   Affero GPL version 3 and may not be removed by you.
    **
    **   0. Attribution Requirement.
    **
    **     You must preserve all legal notices or author attributions in the covered
    **     work or Appropriate Legal Notices displayed by works containing the covered
    **     work.  You may not remove from the covered work any author or developer
    **     credit already included within the covered work.
    **
    **   1. No License To Use Trademarks.
    **
    **     This license does not grant any license or rights to use the trademarks
    **     Golden Code, FWD, any Golden Code or FWD logo, or any other trademarks
    **     of Golden Code Development Corporation. You are not authorized to use the
    **     name Golden Code, FWD, or the names of any author or contributor, for
    **     publicity purposes without written authorization.
    **
    **   2. No Misrepresentation of Affiliation.
    **
    **     You may not represent yourself as Golden Code Development Corporation or FWD.
    **
    **     You may not represent yourself for publicity purposes as associated with
    **     Golden Code Development Corporation, FWD, or any author or contributor to
    **     the covered work, without written authorization.
    **
    **   3. No Misrepresentation of Source or Origin.
    **
    **     You may not represent the covered work as solely your work.  All modified
    **     versions of the covered work must be marked in a reasonable way to make it
    **     clear that the modified work is not originating from Golden Code Development
    **     Corporation or FWD.  All modified versions must contain the notices of
    **     attribution required in this license.
    */

    package com.goldencode.p2j.web;

    import java.io.IOException;
    import java.net.URL;
    import java.net.URLConnection;

    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;

    import org.eclipse.jetty.server.Request;

    /**
     * This handler is responsible to deliver to the client resources stored in a zip file. It is
     * supposed that this zip file containing target resources is available for the context class
     * loader of the thread executing a current request.
     */
    public abstract class AbstractModulesHandler extends AbstractHandlerCommons
    {

       /**
        * Returns true if this handler is responsible for this request, otherwise false.
        *
        *
        * @param    target
        *           The target of the request - either a URI or a name.
        * @param    base
        *           The base request.
        * @param    request
        *           The object or a wrapper of the request.
        *
        * @return   true if this handler must respond on this request
        */
       public abstract boolean isModuleRequest(String             target,
                                               Request            base,
                                               HttpServletRequest request);

       /**
        * Maps the target of the request to its resource name.
        *
        * @param    target
        *           The target of the request - either a URI or a name.
        *
        * @return   The target resource name
        */
       public abstract String mapToResource(String target);

       /**
        * Return a requested module if found or empty response and
        * <code>HttpServletResponse.SC_NOT_FOUND</code> if the module was not found.
        *
        * @param   target
        *          The target of the request - either a URI or a name.
        * @param   base
        *          The base request.
        * @param   request
        *          The object or a wrapper of the request.
        * @param   response
        *          The object or a wrapper of the response.
        */
       public void handle(String              target,
                          Request             base,
                          HttpServletRequest  request,
                          HttpServletResponse response)
       throws IOException,
              ServletException
       {
          if (!base.isHandled() && isModuleRequest(target, base, request))
          {
             // mark request as handled
             base.setHandled(true);
             deliverModule(target, response);
          }
       }

       /**
        * Deliver a module directly from zip file that MUST be on CLASSPATH. In order to work properly
        * this method MUST be synchronized.
        *
        * @param    target
        *           The target of the request - either a URI or a name.
        * @param    response
        *           The details and state of the response.
        *
        * @throws   IOException
        *           ServletException
        *           If any error conditions occur.
        */
       private synchronized void deliverModule(String target, HttpServletResponse response)
       throws IOException,
              ServletException
       {
          String resource = mapToResource(target);

          // load resource
          URL url = Thread.currentThread().getContextClassLoader().getResource(resource);

          if (url != null)
          {
             URLConnection conn = url.openConnection();
             sendResponse(response, conn, resource);
          }
          else
          {
             // module not found
             response.setStatus(HttpServletResponse.SC_NOT_FOUND);
          }
       }
    }