package org.hibernate.id;
import java.io.Serializable;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.hibernate.HibernateException;
import org.hibernate.MappingException;
import org.hibernate.dialect.Dialect;
import org.hibernate.engine.SessionImplementor;
import org.hibernate.exception.JDBCExceptionHelper;
import org.hibernate.mapping.Table;
import org.hibernate.type.Type;
import org.hibernate.util.StringHelper;
/**
* <b>increment</b><br>
* <br>
* An <tt>IdentifierGenerator</tt> that returns a <tt>long</tt>, constructed by
* counting from the maximum primary key value at startup. Not safe for use in a
* cluster!<br>
* <br>
* Mapping parameters supported, but not usually needed: tables, column.
* (The tables parameter specified a comma-separated list of table names.)
*
* @author Gavin King
*/
public class IncrementGenerator implements IdentifierGenerator, Configurable {
private static final Log log = LogFactory.getLog(IncrementGenerator.class);
private long next;
private String sql;
private Class returnClass;
public synchronized Serializable generate(SessionImplementor session, Object object)
throws HibernateException {
if (sql!=null) {
getNext( session );
}
return IdentifierGeneratorFactory.createNumber(next++, returnClass);
}
public void configure(Type type, Properties params, Dialect dialect)
throws MappingException {
String tableList = params.getProperty("tables");
if (tableList==null) tableList = params.getProperty(PersistentIdentifierGenerator.TABLES);
String[] tables = StringHelper.split(", ", tableList);
String column = params.getProperty("column");
if (column==null) column = params.getProperty(PersistentIdentifierGenerator.PK);
String schema = params.getProperty(PersistentIdentifierGenerator.SCHEMA);
String catalog = params.getProperty(PersistentIdentifierGenerator.CATALOG);
returnClass = type.getReturnedClass();
StringBuffer buf = new StringBuffer();
for ( int i=0; i<tables.length; i++ ) {
if (tables.length>1) {
buf.append("select ").append(column).append(" from ");
}
buf.append( Table.qualify( catalog, schema, tables[i] ) );
if ( i<tables.length-1) buf.append(" union ");
}
if (tables.length>1) {
buf.insert(0, "( ").append(" ) ids_");
column = "ids_." + column;
}
sql = "select max(" + column + ") from " + buf.toString();
}
private void getNext( SessionImplementor session ) {
log.debug("fetching initial value: " + sql);
try {
PreparedStatement st = session.getBatcher().prepareSelectStatement(sql);
try {
ResultSet rs = st.executeQuery();
try {
if ( rs.next() ) {
next = rs.getLong(1) + 1;
if ( rs.wasNull() ) next = 1;
}
else {
next = 1;
}
sql=null;
log.debug("first free id: " + next);
}
finally {
rs.close();
}
}
finally {
session.getBatcher().closeStatement(st);
}
}
catch (SQLException sqle) {
throw JDBCExceptionHelper.convert(
session.getFactory().getSQLExceptionConverter(),
sqle,
"could not fetch initial value for increment generator",
sql
);
}
}
}
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