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
   {
   }
}