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;    }  }

}