Unique


1   package org.apache.torque.engine.database.model;
2   
3   /*
4    * Copyright 2001,2004 The Apache Software Foundation.
5    * 
6    * Licensed under the Apache License, Version 2.0 (the "License");
7    * you may not use this file except in compliance with the License.
8    * You may obtain a copy of the License at
9    * 
10   *      http://www.apache.org/licenses/LICENSE-2.0
11   * 
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  import java.util.List  ;
20  
21  /**
22   * Information about unique columns of a table.  This class assumes
23   * that in the underlying RDBMS, unique constraints and unique indices
24   * are roughly equivalent.  For example, adding a unique constraint to
25   * a column also creates an index on that column (this is known to be
26   * true for MySQL and Oracle).
27   *
28   * @author <a HREF="mailto:jvanzyl@apache.org">Jason van Zyl</a>
29   * @author <a HREF="mailto:dlr@collab.net">Daniel Rall</a>
30   * @version $Id: Unique.java,v 1.2 2004/02/22 06:27:19 jmcnally Exp $
31   */
32  public class Unique extends Index
33  {
34      /**
35       * Returns <code>true</code>.
36       *
37       * @return true
38       */
39      public final boolean isUnique()
40      {
41          return true;
42      }
43  
44      /**
45       * String representation of the index. This is an xml representation.
46       *
47       * @return string representation in xml
48       */
49      public String   toString()
50      {
51          StringBuffer   result = new StringBuffer  ();
52          result.append(" <unique name=\"")
53              .append(getName())
54              .append("\">\n");
55  
56          List   columns = getColumns();
57          for (int i = 0; i < columns.size(); i++)
58          {
59              result.append("  <unique-column name=\"")
60                  .append(columns.get(i))
61                  .append("\"/>\n");
62          }
63          result.append(" </unique>\n");
64          return result.toString();
65      }
66  }
67
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