View Javadoc

1   /*
2    * Copyright 2001-2004 The Apache Software Foundation.
3    * 
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    * 
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    * 
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */ 
16  package org.apache.commons.betwixt.io.id;
17  
18  import org.apache.commons.betwixt.io.IDGenerator;
19  
20  /*** <p>Abstract superclass for {@link IDGenerator} implementations.</p>
21    *
22    * <p>It implements the entire <code>IDGenerator</code> interface.
23    * When <code>nextId</code> is called, 
24    * this class sets the <code>LastId</code> property (as well
25    * as returning the value).
26    * Subclasses should override {@link #nextIdImpl}.</p>
27    *
28    * @author <a href="mailto:rdonkin@apache.org">Robert Burrell Donkin</a>
29    * @version $Revision: 155402 $
30    */
31  public abstract class AbstractIDGenerator implements IDGenerator {
32      
33      /*** Last <code>ID</code> returned */
34      private String lastId = "0";
35      
36      /*** 
37       * Gets last <code>ID</code> returned. 
38       *
39       * @return the last id created by the generated
40       */
41      public final String getLastId() {
42          return lastId;
43      }
44      
45      /*** 
46        * <p>Generate next <code>ID</code>.</p>
47        *
48        * <p>This method obtains the next <code>ID</code> from subclass
49        * and then uses this to set the <code>LastId</code> property.</p>
50        *
51        * @return the next id generated 
52        */
53      public final String nextId() {
54          lastId = nextIdImpl();
55          return lastId;
56      }
57      
58      /*** 
59        * Subclasses should <strong>provide an implementation</strong> for this method.
60        * This implementation needs only provide the next <code>ID</code>
61        * value (according to it's algorithm).
62        * Setting the <code>LastId</code> property can be left to this class.
63        *
64        * @return the next id generated
65        */
66      protected abstract String nextIdImpl();
67  }