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Java > Open Source Codes > org > jgroups > persistence > FilePersistenceManager


1 package org.jgroups.persistence;
2
3 /**
4  * @author Mandar Shinde
5  * The class implements the PersistenceManager interface and provides users
6  * a file based implementation when required.
7  * The state of this class is current NOOP. Implementation will be in place
8  * once a better structure for file based properties will be designed.
9  */
10
11
12 import java.io.*;
13 import java.util.*;
14
15 public class FilePersistenceManager implements PersistenceManager
16 {
17     private final File file;
18
19     /**
20      * Default constructor
21      */
22     public FilePersistenceManager(String JavaDoc propertiesFilename)
23         throws Exception JavaDoc
24     {
25         Properties properties = new Properties();
26         properties.load(new FileInputStream(propertiesFilename));
27         String JavaDoc path = properties.getProperty(PersistenceFactory.persistProp);
28         file = new File(path);
29         file.createNewFile();
30     }
31
32     /**
33      * Save new NV pair as serializable objects or if already exist; store
34      * new state
35      */
36     public void save(Serializable key, Serializable val) throws CannotPersistException
37     {
38         try
39         {
40             Map map = retrieveAll();
41             map.put(key, val);
42             saveAll(map);
43         }
44         catch (CannotRetrieveException e)
45         {
46             throw new CannotPersistException(e, "Unable to pre-load existing store.");
47         }
48     }
49
50     /**
51      * Remove existing NV from being persisted
52      */
53     public Serializable remove(Serializable key) throws CannotRemoveException
54     {
55         Object JavaDoc o;
56         try
57         {
58             Map map = retrieveAll();
59             o = map.remove(key);
60             saveAll(map);
61         }
62         catch (CannotRetrieveException e)
63         {
64             throw new CannotRemoveException(e, "Unable to pre-load existing store.");
65         }
66         catch (CannotPersistException e)
67         {
68             throw new CannotRemoveException(e, "Unable to pre-load existing store.");
69         }
70         return (Serializable) o;
71     }
72
73
74     /**
75      * Use to store a complete map into persistent state
76      * @exception CannotPersistException;
77      */
78     public void saveAll(Map map) throws CannotPersistException
79     {
80         try
81         {
82             OutputStream fos = new FileOutputStream(file);
83             Properties prop = new Properties();
84             // NB: For some reason Properties.putAll(map) doesn't seem to work - dimc@users.sourceforge.net
85 for (Iterator iterator = map.entrySet().iterator(); iterator.hasNext();)
86             {
87                 Map.Entry entry = (Map.Entry) iterator.next();
88                 prop.setProperty(entry.getKey().toString(), entry.getValue().toString());
89             }
90             prop.store(fos, null);
91             fos.flush();
92             fos.close();
93         }
94         catch (IOException e)
95         {
96             throw new CannotPersistException(e, "Cannot save to: " + file.getAbsolutePath());
97         }
98     }
99
100
101     /**
102      * Gives back the Map in last known state
103      * @return Map;
104      * @exception CannotRetrieveException;
105      */
106     public Map retrieveAll() throws CannotRetrieveException
107     {
108         try
109         {
110             Properties prop = new Properties();
111             FileInputStream fis = new FileInputStream(file);
112             prop.load(fis);
113             fis.close();
114             return filterLoadedValues(prop);
115         }
116         catch (IOException e)
117         {
118             throw new CannotRetrieveException(e, "Unable to load from file: " + file.getAbsolutePath());
119         }
120     }
121
122     /**
123      * Subclasses should override this method to convert the incoming map
124      * of string/string key/value pairs into the types they want. This
125      * implementation turns the values into Floats to enable
126      * {@link org.jgroups.demos.DistributedHashtableDemo} to work.
127      */
128     protected Map filterLoadedValues(Map in)
129     {
130         Map out = new HashMap();
131         for (Iterator iterator = in.entrySet().iterator(); iterator.hasNext();)
132         {
133             Map.Entry entry = (Map.Entry) iterator.next();
134             out.put(entry.getKey().toString(), Float.valueOf(entry.getValue().toString()));
135         }
136         return out;
137     }
138
139
140     /**
141      * Clears the complete NV state from the DB
142      * @exception CannotRemoveException;
143      x*/
144     public void clear() throws CannotRemoveException
145     {
146         try
147         {
148             saveAll(Collections.EMPTY_MAP);
149         }
150         catch (CannotPersistException e)
151         {
152             throw new CannotRemoveException(e, "Unable to clear map.");
153         }
154     }
155
156
157     /**
158      * Used to handle shutdown call the PersistenceManager implementation.
159      * Persistent engines can leave this implementation empty.
160      */
161     public void shutDown()
162     {
163     return;
164     }
165 }// end of class
166
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