1   /*
2    *  Copyright (c) 1998-2001, The University of Sheffield.
3    *
4    *  This file is part of GATE (see http://gate.ac.uk/), and is free
5    *  software, licenced under the GNU Library General Public License,
6    *  Version 2, June 1991 (in the distribution as file licence.html,
7    *  and also available at http://gate.ac.uk/gate/licence.html).
8    *
9    *  Valentin Tablan 26/10/2001
10   *
11   *  $Id: MapPersistence.java,v 1.2 2001/10/29 17:11:26 valyt Exp $
12   *
13   */
14  package gate.util.persistence;
15  
16  import java.util.*;
17  import java.io.*;
18  
19  import gate.persist.PersistenceException;
20  import gate.creole.ResourceInstantiationException;
21  
22  public class MapPersistence implements Persistence {
23    /**
24     * Populates this Persistence with the data that needs to be stored from the
25     * original source object.
26     */
27    public void extractDataFromSource(Object source)throws PersistenceException{
28      if(! (source instanceof Map)){
29        throw new UnsupportedOperationException(
30                  getClass().getName() + " can only be used for " +
31                  Map.class.getName() +
32                  " objects!\n" + source.getClass().getName() +
33                  " is not a " + Map.class.getName());
34      }
35      mapType = source.getClass();
36  
37      Map map = (Map)source;
38      List keysList = new ArrayList();
39      List valuesList = new ArrayList();
40      localMap = new HashMap(map.size());
41      //collect the keys in the order given by the entrySet().iterator();
42      Iterator keyIter = map.keySet().iterator();
43      while(keyIter.hasNext()){
44        Object key = keyIter.next();
45        Object value = map.get(key);
46  
47        key = PersistenceManager.getPersistentRepresentation(key);
48        value = PersistenceManager.getPersistentRepresentation(value);
49        localMap.put(key, value);
50      }
51    }
52  
53    /**
54     * Creates a new object from the data contained. This new object is supposed
55     * to be a copy for the original object used as source for data extraction.
56     */
57    public Object createObject()throws PersistenceException,
58                                       ResourceInstantiationException{
59      //let's try to create a map of the same type as the original
60      Map result = null;
61      try{
62        result = (Map)mapType.newInstance();
63      }catch(Exception e){
64      }
65      if(result == null) result = new HashMap(localMap.size());
66  
67      //now we have a map let's populate it
68      Iterator keyIter = localMap.keySet().iterator();
69      while(keyIter.hasNext()){
70        Object key = keyIter.next();
71        Object value = localMap.get(key);
72  
73        key = PersistenceManager.getTransientRepresentation(key);
74        value = PersistenceManager.getTransientRepresentation(value);
75        result.put(key, value);
76      }
77  
78      return result;
79    }
80  
81    protected Class mapType;
82    protected HashMap localMap;
83    static final long serialVersionUID = 1835776085941379996L;
84  }