继承jdbcDaoSupport的jdbc查询速度问题，高手帮助

数据库：oracle9i

应用服务器：tomcat6
查询调用 jdbcTemplate().queryForList(

StringBuffer sb = new StringBuffer();
  sb.append(" SELECT PLU_CODE,PLU_VALUE,MEASURE_TIME,EQP_ID FROM  E_DATA_VALUE ");
  sb.append(" WHERE  EQP_ID=? AND MEASURE_TIME BETWEEN ? AND ? ");*/
  
  System.out.println(System.currentTimeMillis());
  List rsop = getJdbcTemplate().queryForList(sb.toString(),param);
  System.out.println(System.currentTimeMillis());

速度非常慢，表中已经分区，数据大有5000万条，查询要30秒左右

DataSource ds = this.getDataSource();  
        Connection con = null;
        PreparedStatement pstmt = null;
        ResultSet rs =null;
        try {

            con = ds.getConnection();            
           {            
               pstmt = con.prepareStatement("SELECT PLU_CODE,PLU_VALUE,MEASURE_TIME,EQP_ID FROM  E_DATA_VALUE   WHERE  EQP_ID=? AND MEASURE_TIME BETWEEN to_date(?,'yyyy-mm-dd hh24:mi:ss')  AND to_date(?,'yyyy-mm-dd hh24:mi:ss') ");
               pstmt.setInt(1, eqpId);
               pstmt.setString(2,qd.getBeginTime());
               pstmt.setString(3, qd.getEndTime());
               rs = pstmt.executeQuery();              
            }
        }
        catch( Exception sqle ) {
          ds = null;
            con = null;
            pstmt = null;
       }finally{
          ds = null;
            con = null;
            pstmt = null;
       }这种方式，查询只要<1秒， 可是无法释放连接池，大概一天时间后，就会连接池耗尽

不知道有没有好的办法实现解决getJdbcTemplate().queryForList(sb.toString(),param);查询慢的问题，困扰！