oracle中如何使用序列

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//sequenceName为序列名，length为显示序列的长度例如显示为（0000001）

public String getCircSequence(String sequenceName, int length) throws CircException
    {

        Connection conn = null;
        StringBuffer sb = null;

        try
        {
            conn =JdbcConnection.getInstance().getConnection();//获取链接
            int key = nextSequenceNumber(conn, sequenceName);//获取序列
            if (key <= 0) return null;
            sb = new StringBuffer(length);
            String k = Integer.toString(key);

            //想要显示的长度减掉获取序列的长度，将得到的长度用0 补位
            int padSize = length - k.length();
            for (int i = 0; i < padSize; i++) sb.append('0');
            sb.append(key);

        } catch (Throwable e)
        {
            e.printStackTrace();
            throw new CircException(kDBReadError);

        } finally
        {
            try
            {
                if (conn != null) conn.close();
            } catch (Throwable e)
            {
                e.printStackTrace();
            }
        }

        if (sb != null) return new String(sb);
        else return null;
    }

//获知取序列

public int nextSequenceNumber(Connection cc, String seqName) throws SQLException
    {
        if (cc == null) throw new SQLException();
        int k = 0;
        Statement stat = cc.createStatement();
        ResultSet rs = stat.executeQuery("SELECT "+seqName+".nextval from dual");
        if (rs != null && rs.next())
            k = rs.getInt(1);
        rs.close();
        stat.close();

return k;
}

public static void main(String[] args)
    {
        CircSequence circSequence = new CircSequence();
        try
        {
            String seq = circSequence.getCircSequence("CIR_SEQ_USL_V_USERID", 10);
            System.out.println(seq);
        } catch (Throwable e)
        {
            e.printStackTrace();
        }
    }