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1
43 package org.exolab.jms.persistence;
44
45 import java.sql.Connection  ;
46 import java.sql.PreparedStatement ;
47 import java.sql.ResultSet ;
48
49
50
57 public class SeedGenerator {
58
59
62 private static SeedGenerator _instance;
63
64
68 private static final Object _block = new Object ();
69
70
71
79 public static SeedGenerator instance() {
80 return _instance;
81 }
82
83
88 public static SeedGenerator initialise() {
89 if (_instance == null) {
90 synchronized (_block) {
91 if (_instance == null) {
92 _instance = new SeedGenerator();
93 }
94 }
95 }
96
97 return _instance;
98 }
99
100
108 public synchronized long next(Connection connection, String name)
109 throws PersistenceException {
110
111 PreparedStatement select = null;
112 PreparedStatement update = null;
113 PreparedStatement insert = null;
114 ResultSet result = null;
115 long value = 0;
116
117 boolean successful = false;
118 try {
119 select = connection.prepareStatement(
120 "select seed from seeds where name=?");
121 select.setString(1, name);
122
123 result = select.executeQuery();
124 if (result.next()) {
125 value = result.getLong(1);
126 value++;
127 update = connection.prepareStatement(
128 "update seeds set seed=? where name=?");
129 update.setLong(1, value);
130 update.setString(2, name);
131 update.executeUpdate();
132 } else {
133 value = 1;
134 insert = connection.prepareStatement(
135 "insert into seeds (name, seed) values (?,?)");
136 insert.setString(1, name);
137 insert.setLong(2, value);
138 insert.executeUpdate();
139 }
140 } catch (Exception exception) {
141 throw new PersistenceException("next " + exception.getMessage());
142 } finally {
143 SQLHelper.close(result);
144 SQLHelper.close(select);
145 SQLHelper.close(update);
146 SQLHelper.close(insert);
147 }
148
149 return value;
150 }
151
152
159 public void removeAll(Connection connection)
160 throws PersistenceException {
161
162 PreparedStatement delete = null;
163 try {
164 delete = connection.prepareStatement("delete from seeds");
165 delete.executeUpdate();
166 } catch (Exception error) {
167 throw new PersistenceException("Failed in removeAll with " +
168 error.toString());
169 } finally {
170 SQLHelper.close(delete);
171 }
172 }
173
174
178 public void close() {
179 _instance = null;
180 }
181
182
185 protected SeedGenerator() {
186 }
187 }
188 |
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