# ContextAwareThread.java

    /*
    ** Module   : ContextAwareThread.java
    ** Abstract : a thread which sets the given security context for the duration of the core logic
    **
    ** Copyright (c) 2011-2023, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- --------------------------------Description----------------------------------
    ** 001 GES 20200204 First version, which is based on refactored logic from AssociatedThread.
    ** 002 IAS 29219422 Make ContextAwareThread daemon by default
    ** 003 GBB 20230825 SecurityManager context methods calls updated.
    */

    /*
    ** 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.security;

    /**
     * Provides a thread which automatically sets the security context for the duration of the core
     * logic execution.  When the thread exits, it will automatically cleanup the context
     * (decrementing the reference counts of any resources and so forth).
     * <p>
     * This class is intentionally made package-private because it MUST not be accessible to
     * external code.
     */
    class ContextAwareThread
    extends Thread
    {
       /** Security Manager instance (it is singleton so it is safe as a static). */
       protected static final SecurityManager sm = SecurityManager.getInstance();

       /** The core logic that will be executed. */
       private final Runnable core;

       /** The security context of the instantiating thread. */
       protected final SecurityContextStack stack;

       /**
        * Constructor which allows the core logic to be specified.
        *
        * @param    core
        *           The logic to execute when the thread is started.  Must not be {@code null}.
        * @param    stack
        *           The security context to set for the duration of the core logic execution.
        *
        * @throws   NullPointerException
        *           If the instantiating thread has no security context or if any parameter is
        *           {@code null}.
        */
       public ContextAwareThread(Runnable core, SecurityContextStack stack)
       throws NullPointerException
       {
          super();

          if (core == null)
          {
             throw new NullPointerException("Core logic must be specified!");
          }

          if (sm.isServer() && stack == null)
          {
             throw new NullPointerException("Security context must be specified!");
          }

          this.core  = core;
          this.stack = stack;
          setDaemon(true);
       }

       /**
        * This method will be invoked when the thread is started, it sets up the initial security
        * context as obtained from the instantiating thread, then it will execute the core logic
        * specified by the caller and drop the security context after that logic is done.
        */
       @Override
       public void run()
       {
          // server-side processing needs a context to work properly and this is a new thread
          if (sm.isServer())
          {
             sm.contextSm.forceSecurityContext(stack, needsSession());
          }

          try
          {
             core.run();
          }

          finally
          {
             // cleanup processing
             if (sm.isServer())
             {
                try
                {
                   sm.contextSm.popAllSecurityContext();
                }

                catch (RestrictedUseException rue)
                {
                   // should not happen
                }
             }
          }
       }

       /**
        * Report if this thread should create a new session when the security context is pushed or if
        * the existing session should be reused.
        *
        * @return   {@code true} if a new session must be created.
        */
       public boolean needsSession()
       {
          return false;
       }
    }