FieldEntry.java

/*
** Module   : FieldEntry.java
** Abstract : abstract base class for passing data lists to I/O helpers
**
** Copyright (c) 2006-2024, Golden Code Development Corporation.
**
** -#- -I- --Date-- --JPRM-- -----------------------------Description-----------------------------
** 001 GES 20060925   @29899 Created initial version as abstract base class for passing data lists
**                           to I/O helpers.
** 002 SIY 20071001   @35315 Made class suitable for network transfers. Ref: #35314
** 003 SIY 20071003   @35348 Added resolveData() method. Header cleanup. Ref: #35347.
** 004 CA  20170827          Added support for dynamic array expansion.
** 005 VVT 20241107          NPE in toArray fixed: the method should support nulls in the input array.
**                           See #9303.
*/ 
/*
** 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.
** 
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** 
**     This license does not grant any license or rights to use the trademarks
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**     name Golden Code, FWD, or the names of any author or contributor, for
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*/

package com.goldencode.p2j.util;

import java.io.Externalizable;
import java.util.*;

/**
 * This class provides an abstract base for passing data lists to I/O helpers. 
 */
public abstract class FieldEntry
implements Externalizable
{
   /**
    * Resolve the entries in the given array.  These can be individual {@link FieldEntry} instances
    * or {@link ExtentExpansion} instances - in the later case, we rely on calling 
    * {@link ExtentExpansion#expand()} to get us the array.
    * 
    * @param    entries
    *           The entries to resolve.
    *           
    * @return   See above.
    */
   @SuppressWarnings("unchecked")
   public static FieldEntry[] toArray(Object... entries)
   {
      List<FieldEntry> res = new LinkedList<>();
      
      for (Object entry : entries)
      {
         if (entry == null)
         {
            continue;
         }
         
         if (entry instanceof FieldEntry)
         {
            res.add((FieldEntry) entry);
         }
         else if (entry instanceof ExtentExpansion)
         {
            res.addAll(Arrays.asList(((ExtentExpansion<FieldEntry>) entry).expand()));
         }
         else
         {
            throw new IllegalArgumentException("Could not resolve " + entry.getClass() + "!");
         }
      }
      
      return res.toArray(new FieldEntry[0]);
   }

   /**
    * Renders the contained field definition to the given stream.
    *
    * @param    out
    *           The stream to which the field should be rendered.
    *           
    * @throws   ErrorConditionException
    *           On any error during I/O. 
    */
   public abstract void output(Stream out)
   throws ErrorConditionException;
   
   /**
    * Notify instance that it is about to be transferred so all resolvable
    * data should be resolved and prepared for sending via network.
    */
   public abstract void resolveData();
}