Configuration


1   /**
2    * This file is part of Presumo.
3    *
4    * Presumo is free software; you can redistribute it and/or modify
5    * it under the terms of the GNU General Public License as published by
6    * the Free Software Foundation; either version 2 of the License, or
7    * (at your option) any later version.
8    *
9    * Presumo is distributed in the hope that it will be useful,
10   * but WITHOUT ANY WARRANTY; without even the implied warranty of
11   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12   * GNU General Public License for more details.
13   *
14   * You should have received a copy of the GNU General Public License
15   * along with Presumo; if not, write to the Free Software
16   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
17   *
18   *
19   * Copyright 2001 Dan Greff
20   */
21  package com.presumo.util.config;
22  
23  import java.util.Enumeration  ;
24  import java.util.StringTokenizer  ;
25  
26  /**
27   * This class along with Preferences abstracts out what configuration
28   * subsystem is being used from the JMS implementation.
29   * 
30   * @author Dan Greff
31   */
32  public abstract class Configuration 
33  {
34    private static Configuration onlyInstance;
35    
36    /**
37     * Access point for the configuration abstraction layer.
38     */
39    public static Configuration getInstance()
40    {
41      if (onlyInstance == null)
42        onlyInstance = new PropertyFileConfiguration();
43       
44      return onlyInstance;
45    }
46    
47    /**
48     * Convience method to parse a list from configuration.
49     *
50     * @returns Each element in the list.  The return value
51     *          will never be null.
52     */
53    public static String  [] parseList(String   list, String   delim)
54    {
55      String   [] retval = null;
56      if (list == null) {
57        retval = new String  [0];
58        return retval;
59      } if (delim == null) {
60        retval = new String  [1];
61        retval[0] = list;
62        return retval;
63      }
64     
65      StringTokenizer   tokens = new StringTokenizer  (list, delim);
66      int size = tokens.countTokens();
67      retval = new String  [size];
68      
69      for (int i=0; i < size; ++i)
70        retval[i] = tokens.nextToken().trim();
71        
72      return retval;
73    }
74    
75    /**
76     * Used to retrieve the preferences object for the entire system.
77     *
78     * @return The preference object, or null if an error occurred.
79     */
80    public abstract Preferences getSystemPreferences();
81    
82    /**
83     * Used to retrieve the preferences object for the specified subsystem.
84     *
85     * @return The preference object if found, or null if an error occurred
86     *         or it was not found.
87     */
88    public abstract Preferences getSubsystemPreferences(String   subsystem);
89   
90    /**
91     * List all subsystems containing configuration.
92     *
93     */
94    public abstract Enumeration   getSubsystems();
95      
96  }
97
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