一个生成唯一序号的服务，虽然技术不先进，但是很好用

package com.highcom.seqgen.dao.jdbc;

import java.sql.*;
import javax.sql.*;

import org.apache.commons.logging.*;
import org.springframework.beans.factory.*;
import org.springframework.context.*;
import org.springframework.jdbc.core.*;
import org.springframework.jdbc.object.*;
import com.highcom.seqgen.dao.*;
import com.highcom.seqgen.domain.*;

public class SequenceDaoJdbcImpl
implements SequenceDao, InitializingBean {

private DataSource dataSource;
private static Log logger = LogFactory.getLog(SequenceDaoJdbcImpl.class);

//
SequenceQuery sequenceQuery;
SequenceUpdate sequenceUpdate;
SequenceInsert sequenceInsert;
//
protected static final String INSERT_SQL =
"insert into sequence(seq_name,seq_value) values( ? , ? )";
protected static final String UPDATE_SQL =
"update sequence set seq_value = ? where seq_name = ?";
protected static final String SELECT_SQL =
"select seq_name,seq_value from sequence where seq_name =?";

public SequenceDaoJdbcImpl() {

}

public int getSequence(String seq_name) {
int result;
Object obj = sequenceQuery.findObject(new Object[] {seq_name});
if (obj == null) {
sequenceInsert.insert(seq_name, 0);
}

Sequence seq = (Sequence) sequenceQuery.findObject(new Object[] {seq_name});
sequenceUpdate.update(seq.getName(), seq.getValue() + 1);
result = seq.getValue() + 1;
return result;
}

public void afterPropertiesSet() throws Exception {
if (dataSource == null) {
logger.error("Must set dataSource bean property on " + getClass());
throw new ApplicationContextException(
"Must set dataSource bean property on " + getClass());
}
//
sequenceQuery = new SequenceQuery(this.dataSource);
sequenceUpdate = new SequenceUpdate(this.dataSource);
sequenceInsert = new SequenceInsert(this.dataSource);
}

public void setDataSource(DataSource dataSource) {
this.dataSource = dataSource;
}

///////////////////////jdbc内部类
class SequenceInsert
extends SqlUpdate {
public SequenceInsert(DataSource dataSource) {
super(dataSource, INSERT_SQL);
declareParameter(new SqlParameter(Types.VARCHAR));
declareParameter(new SqlParameter(Types.INTEGER));
compile();
}

public void insert(String seqName, int segValue) {
Object[] objs = new Object[] {
seqName, new Integer(segValue)};
super.update(objs);
}
}

class SequenceUpdate
extends SqlUpdate {
public SequenceUpdate(DataSource dataSource) {
super(dataSource, UPDATE_SQL);
declareParameter(new SqlParameter(Types.INTEGER));
declareParameter(new SqlParameter(Types.VARCHAR));

compile();

}

public void update(String seqName, int segValue) {
Object[] objs = new Object[] {
new Integer(segValue), seqName};
super.update(objs);
}
}

class SequenceQuery
extends MappingSqlQuery {
public SequenceQuery(DataSource dataSource) {
super(dataSource, SELECT_SQL);
declareParameter(new SqlParameter(Types.VARCHAR));
compile();
}

protected Object mapRow(ResultSet resultSet, int _int) throws SQLException {
Sequence seq = new Sequence();
seq.setName(resultSet.getString("seq_name"));
seq.setValue(resultSet.getInt("seq_value"));
return seq;
}
}

}