spring HsqlMaxValueIncrementer 源码
spring HsqlMaxValueIncrementer 代码
文件路径：/spring-jdbc/src/main/java/org/springframework/jdbc/support/incrementer/HsqlMaxValueIncrementer.java
/*
* Copyright 2002-2014 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.jdbc.support.incrementer;
import javax.sql.DataSource;
/**
* {@link DataFieldMaxValueIncrementer} that increments the maximum value of a given HSQL table
* with the equivalent of an auto-increment column. Note: If you use this class, your HSQL
* key column should <i>NOT</i> be auto-increment, as the sequence table does the job.
*
* <p>The sequence is kept in a table. There should be one sequence table per
* table that needs an auto-generated key.
*
* <p>Example:
*
* <pre class="code">create table tab (id int not null primary key, text varchar(100));
* create table tab_sequence (value identity);
* insert into tab_sequence values(0);</pre>
*
* If "cacheSize" is set, the intermediate values are served without querying the
* database. If the server or your application is stopped or crashes or a transaction
* is rolled back, the unused values will never be served. The maximum hole size in
* numbering is consequently the value of cacheSize.
*
* <p><b>NOTE:</b> HSQL now supports sequences and you should consider using them instead:
* {@link HsqlSequenceMaxValueIncrementer}
*
* @author Jean-Pierre Pawlak
* @author Thomas Risberg
* @author Juergen Hoeller
* @see HsqlSequenceMaxValueIncrementer
*/
public class HsqlMaxValueIncrementer extends AbstractIdentityColumnMaxValueIncrementer {
/**
* Default constructor for bean property style usage.
* @see #setDataSource
* @see #setIncrementerName
* @see #setColumnName
*/
public HsqlMaxValueIncrementer() {
}
/**
* Convenience constructor.
* @param dataSource the DataSource to use
* @param incrementerName the name of the sequence/table to use
* @param columnName the name of the column in the sequence table to use
*/
public HsqlMaxValueIncrementer(DataSource dataSource, String incrementerName, String columnName) {
super(dataSource, incrementerName, columnName);
}
@Override
protected String getIncrementStatement() {
return "insert into " + getIncrementerName() + " values(null)";
}
@Override
protected String getIdentityStatement() {
return "select max(identity()) from " + getIncrementerName();
}
}
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