1     /** 2      * 根据表名生成该表的序列 3      * @param tableName 4      * @return 返回生成的序列 5      */ 6     //全局方法 -加锁 7     //public static synchronized int generate(String tableName) {    8     //局部成员方法-加锁 9     //public synchronized int generate(String tableName) {10         //synchronized(this) {
    11     public static int generate(String tableName) {12         //使用数据库的悲观锁for update13         String sql = "select value from t_table_id where table_name=? for update";14         Connection conn = null;15         PreparedStatement pstmt = null;16         ResultSet rs = null;17         int value = 0;18         try {19             conn = DbUtil.getConnection();20             //开始事务21             DbUtil.beginTransaction(conn);22             pstmt = conn.prepareStatement(sql);23             pstmt.setString(1, tableName);24             rs = pstmt.executeQuery();25             if (!rs.next()) {26                 throw new RuntimeException();27             }28             value = rs.getInt("value");29             value++; //自加30             modifyValueField(conn, tableName, value);31             //提交事务32             DbUtil.commitTransaction(conn);33         }catch(Exception e) {34             e.printStackTrace();35             //回滚事务36             DbUtil.rollbackTransaction(conn);37             throw new RuntimeException();38         }finally {39             DbUtil.close(rs);40             DbUtil.close(pstmt);41             DbUtil.resetConnection(conn); //重置Connection的状态42             DbUtil.close(conn);43         }44         return value;45     }

 

总结：不断提高自己编程效率！