UCDeleteProduct


1   package org.apache.ojb.tutorial2;
2   
3   /* Copyright 2002-2004 The Apache Software Foundation
4    *
5    * Licensed under the Apache License, Version 2.0 (the "License");
6    * you may not use this file except in compliance with the License.
7    * You may obtain a copy of the License at
8    *
9    *     http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  
18  import java.util.List  ;
19  
20  import org.odmg.Implementation;
21  import org.odmg.Database;
22  import org.odmg.Transaction;
23  import org.odmg.OQLQuery;
24  
25  /**
26   * Use case for deleting a product from the database.
27   */
28  public class UCDeleteProduct extends AbstractUseCase
29  {
30      /**
31       * Creates a new delete use case instance.
32       * 
33       * @param odmg The odmg implementation to use
34       */
35      public UCDeleteProduct(Implementation odmg)
36      {
37          super(odmg);
38      }
39  
40      /**
41       * Returns a description of this use case.
42       * 
43       * @return A description of the use case
44       */
45      public String   getDescription()
46      {
47          return "Delete a product entry";
48      }
49  
50      /**
51       * Performs this use case.
52       */
53      public void apply()
54      {
55          String   in = readLineWithMessage("Delete Product with id:");
56          int    id = Integer.parseInt(in);
57  
58          // We don't have a reference to the selected Product.
59          // So first we have to lookup the object.
60  
61          // 1. build oql query to select product by id:
62          String   oqlQuery = "select del from " + Product.class.getName() + " where id = " + id;
63  
64          Database    db = odmg.getDatabase(null); // the current DB
65          Transaction tx = null;
66  
67          try
68          {
69              // 2. start transaction
70              tx = odmg.newTransaction();
71              tx.begin();
72  
73              // 3. lookup the product specified by query
74              OQLQuery query = odmg.newOQLQuery();
75  
76              query.create(oqlQuery);
77  
78              List     result      = (List  )query.execute();
79              Product toBeDeleted = (Product)result.get(0);
80  
81              // 4. now mark object for deletion
82              db.deletePersistent(toBeDeleted);
83              // 5. commit transaction
84              tx.commit();
85          }
86          catch (Throwable   t)
87          {
88              // rollback in case of errors
89              tx.abort();
90              t.printStackTrace();
91          }
92      }
93  }
94
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