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Java > Open Source Codes > org > apache > cayenne > dba > derby > DerbyPkGenerator


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19
20 package org.apache.cayenne.dba.derby;
21
22 import java.sql.Connection JavaDoc;
23 import java.sql.PreparedStatement JavaDoc;
24 import java.sql.ResultSet JavaDoc;
25 import java.util.Collections JavaDoc;
26
27 import org.apache.cayenne.CayenneException;
28 import org.apache.cayenne.access.DataNode;
29 import org.apache.cayenne.access.QueryLogger;
30 import org.apache.cayenne.dba.JdbcPkGenerator;
31 import org.apache.cayenne.map.DbEntity;
32
33 /**
34  * Default PK generator for Derby that uses updateable ResultSet to get the next id from
35  * the lookup table.
36  *
37  * @since 1.2
38  * @author Andrus Adamchik
39  */
40 public class DerbyPkGenerator extends JdbcPkGenerator {
41
42     static final String JavaDoc SELECT_QUERY = "SELECT NEXT_ID FROM AUTO_PK_SUPPORT"
43             + " WHERE TABLE_NAME = ? FOR UPDATE";
44
45     protected int pkFromDatabase(DataNode node, DbEntity entity) throws Exception JavaDoc {
46
47         if (QueryLogger.isLoggable()) {
48             QueryLogger.logQuery(SELECT_QUERY, Collections
49                     .singletonList(entity.getName()));
50         }
51
52         Connection JavaDoc c = node.getDataSource().getConnection();
53
54         try {
55             PreparedStatement JavaDoc select = c.prepareStatement(
56                     SELECT_QUERY,
57                     ResultSet.TYPE_FORWARD_ONLY,
58                     ResultSet.CONCUR_UPDATABLE);
59
60             select.setString(1, entity.getName());
61             ResultSet JavaDoc rs = select.executeQuery();
62
63             if (!rs.next()) {
64                 throw new CayenneException("PK lookup failed for table: "
65                         + entity.getName());
66             }
67
68             int nextId = rs.getInt(1);
69
70             rs.updateInt(1, nextId + pkCacheSize);
71             rs.updateRow();
72
73             if (rs.next()) {
74                 throw new CayenneException("More than one PK record for table: "
75                         + entity.getName());
76             }
77             
78             rs.close();
79
80             select.close();
81             c.commit();
82
83             return nextId;
84         }
85         finally {
86             c.close();
87         }
88     }
89 }
90
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