# CurrentRequestFilter.java

    /*
    ** Module   : CurrentRequestFilter.java
    ** Abstract : A filter to save as thread-local the current HttpServletRequest instance.
    **
    ** Copyright (c) 2021, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- ------------------------------Description----------------------------------
    ** 001 CA  20211214 Created initial version.
    */
    /*
    ** 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.*;

    import javax.servlet.*;
    import javax.servlet.http.*;

    /**
     * Save the current {@link HttpServletRequest} instance as thread-local, so it is available without any
     * other injection, from the current thread, by calling {@link #getCurrentRequest()}.
     */
    public class CurrentRequestFilter
    implements Filter
    {
       /** The current request being processed, on this thread. */
       private static ThreadLocal<HttpServletRequest> currentRequest = new ThreadLocal<>();

       /**
        * Get the current servlet request, being executed on this thread.  This will return a non-null
        * value only for the duration of the request.
        *
        * @return   See above.
        */
       public static HttpServletRequest getCurrentRequest()
       {
          return currentRequest.get();
       }

       /**
        * Filter the web request by caching this thread's servlet request instance, to be available while
        * processing the request.
        *
        * @param    request
        *           The servlet request.
        * @param    response
        *           The servlet response.
        * @param    filter
        *           The filter chain.
        */
       @Override
       public void doFilter(ServletRequest request, ServletResponse response, FilterChain filter)
       throws IOException,
              ServletException
       {
          if (request instanceof HttpServletRequest)
          {
             currentRequest.set((HttpServletRequest) request);

             try
             {
                filter.doFilter(request, response);
             }
             finally
             {
                currentRequest.set(null);
             }
          }
       }

       /**
        * No-op.
        */
       @Override
       public void destroy()
       {
       }

       /**
        * No-op.
        */
       @Override
       public void init(FilterConfig arg0)
       throws ServletException
       {
       }
    }