Source Code Cross Referenced for MySQLMaxValueIncrementer.java in  » J2EE » spring-framework-2.0.6 » org » springframework » jdbc » support » incrementer » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » J2EE » spring framework 2.0.6 » org.springframework.jdbc.support.incrementer 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /*
002:         * Copyright 2002-2007 the original author or authors.
003:         *
004:         * Licensed under the Apache License, Version 2.0 (the "License");
005:         * you may not use this file except in compliance with the License.
006:         * You may obtain a copy of the License at
007:         *
008:         *      http://www.apache.org/licenses/LICENSE-2.0
009:         *
010:         * Unless required by applicable law or agreed to in writing, software
011:         * distributed under the License is distributed on an "AS IS" BASIS,
012:         * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013:         * See the License for the specific language governing permissions and
014:         * limitations under the License.
015:         */
016:
017:        package org.springframework.jdbc.support.incrementer;
018:
019:        import java.sql.Connection;
020:        import java.sql.ResultSet;
021:        import java.sql.SQLException;
022:        import java.sql.Statement;
023:
024:        import javax.sql.DataSource;
025:
026:        import org.springframework.dao.DataAccessException;
027:        import org.springframework.dao.DataAccessResourceFailureException;
028:        import org.springframework.jdbc.datasource.DataSourceUtils;
029:        import org.springframework.jdbc.support.JdbcUtils;
030:
031:        /**
032:         * Class to increment maximum value of a given MySQL table with the equivalent
033:         * of an auto-increment column. Note: If you use this class, your MySQL key
034:         * column should <i>NOT</i> be auto-increment, as the sequence table does the job.
035:         *
036:         * <p>The sequence is kept in a table; there should be one sequence table per
037:         * table that needs an auto-generated key. The table type of the sequence table
038:         * should be MyISAM so the sequences are allocated without regard to any
039:         * transactions that might be in progress.
040:         *
041:         * <p>Example:
042:         *
043:         * <pre class="code">create table tab (id int unsigned not null primary key, text varchar(100));
044:         * create table tab_sequence (value int not null) type=MYISAM;
045:         * insert into tab_sequence values(0);</pre>
046:         *
047:         * If cacheSize is set, the intermediate values are served without querying the
048:         * database. If the server or your application is stopped or crashes or a transaction
049:         * is rolled back, the unused values will never be served. The maximum hole size in
050:         * numbering is consequently the value of cacheSize.
051:         *
052:         * @author Jean-Pierre Pawlak
053:         * @author Thomas Risberg
054:         * @author Juergen Hoeller
055:         */
056:        public class MySQLMaxValueIncrementer extends
057:                AbstractDataFieldMaxValueIncrementer {
058:
059:            /** The Sql string for retrieving the new sequence value */
060:            private static final String VALUE_SQL = "select last_insert_id()";
061:
062:            /** The name of the column for this sequence */
063:            private String columnName;
064:
065:            /** The number of keys buffered in a cache */
066:            private int cacheSize = 1;
067:
068:            /** The next id to serve */
069:            private long nextId = 0;
070:
071:            /** The max id to serve */
072:            private long maxId = 0;
073:
074:            /**
075:             * Default constructor.
076:             **/
077:            public MySQLMaxValueIncrementer() {
078:            }
079:
080:            /**
081:             * Convenience constructor.
082:             * @param ds the DataSource to use
083:             * @param incrementerName the name of the sequence/table to use
084:             * @param columnName the name of the column in the sequence table to use
085:             **/
086:            public MySQLMaxValueIncrementer(DataSource ds,
087:                    String incrementerName, String columnName) {
088:                setDataSource(ds);
089:                setIncrementerName(incrementerName);
090:                this .columnName = columnName;
091:                afterPropertiesSet();
092:            }
093:
094:            /**
095:             * Set the name of the column in the sequence table.
096:             */
097:            public void setColumnName(String columnName) {
098:                this .columnName = columnName;
099:            }
100:
101:            /**
102:             * Return the name of the column in the sequence table.
103:             */
104:            public String getColumnName() {
105:                return this .columnName;
106:            }
107:
108:            /**
109:             * Set the number of buffered keys.
110:             */
111:            public void setCacheSize(int cacheSize) {
112:                this .cacheSize = cacheSize;
113:            }
114:
115:            /**
116:             * Return the number of buffered keys.
117:             */
118:            public int getCacheSize() {
119:                return this .cacheSize;
120:            }
121:
122:            public void afterPropertiesSet() {
123:                super .afterPropertiesSet();
124:                if (this .columnName == null) {
125:                    throw new IllegalArgumentException("columnName is required");
126:                }
127:            }
128:
129:            protected synchronized long getNextKey() throws DataAccessException {
130:                if (this .maxId == this .nextId) {
131:                    /*
132:                     * Need to use straight JDBC code because we need to make sure that the insert and select
133:                     * are performed on the same connection (otherwise we can't be sure that last_insert_id()
134:                     * returned the correct value)
135:                     */
136:                    Connection con = DataSourceUtils
137:                            .getConnection(getDataSource());
138:                    Statement stmt = null;
139:                    try {
140:                        stmt = con.createStatement();
141:                        DataSourceUtils.applyTransactionTimeout(stmt,
142:                                getDataSource());
143:                        // increment the sequence column
144:                        stmt.executeUpdate("update " + getIncrementerName()
145:                                + " set " + this .columnName
146:                                + " = last_insert_id(" + this .columnName
147:                                + " + " + getCacheSize() + ")");
148:                        // retrieve the new max of the sequence column
149:                        ResultSet rs = stmt.executeQuery(VALUE_SQL);
150:                        try {
151:                            if (!rs.next()) {
152:                                throw new DataAccessResourceFailureException(
153:                                        "last_insert_id() failed after executing an update");
154:                            }
155:                            this .maxId = rs.getLong(1);
156:                        } finally {
157:                            JdbcUtils.closeResultSet(rs);
158:                        }
159:                        this .nextId = this .maxId - getCacheSize() + 1;
160:                    } catch (SQLException ex) {
161:                        throw new DataAccessResourceFailureException(
162:                                "Could not obtain last_insert_id()", ex);
163:                    } finally {
164:                        JdbcUtils.closeStatement(stmt);
165:                        DataSourceUtils.releaseConnection(con, getDataSource());
166:                    }
167:                } else {
168:                    this.nextId++;
169:                }
170:                return this.nextId;
171:            }
172:
173:        }
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