这个JAVA事务问题在哪？为什么有时候只减了汇款者金额却没给收款者加？

	public boolean agentUpdateCustomerBalance(int agent_id,String  username,int count)//代理给客户

	

	{

		DBHelper helper=new DBHelper();

		Connection conn=helper.getConn();

		

		int res=0;

		try

		{

			conn.setAutoCommit(false);

			conn.setTransactionIsolation(Connection.TRANSACTION_SERIALIZABLE);

			

			

			PreparedStatement ps=helper.createPreparedStatement("select balance from boss_agent where id=?");

			ps.setInt(1,agent_id);

			ResultSet rs=ps.executeQuery();

			if(rs.next()&& rs.getInt("balance")-count>=0)

			{

				ps=helper.createPreparedStatement("select money_remain from users  where username=?");

				ps.setString(1, username);

				rs=ps.executeQuery();

				if(rs.next()&& rs.getInt("money_remain")+count>=0)

				{

//					conn.setAutoCommit(false);

//					conn.setTransactionIsolation(Connection.TRANSACTION_SERIALIZABLE);

					

					

					ps=helper.createPreparedStatement("update boss_agent set balance=ifnull(balance,0)-(?) where id=?");

					ps.setInt(1, count);

					ps.setInt(2, agent_id);

					res+=ps.executeUpdate();

					System.out.println("Jian"+ps.toString());

					

					ps=helper.createPreparedStatement("update users set money_remain=ifnull(money_remain,0)+(?) where username=?");

					ps.setInt(1, count);

					ps.setString(2, username);	

					res+=ps.executeUpdate();

					System.out.println("Jia"+ps.toString());

					

					if(res==2){

						System.out.println("conn.commit();2");

						conn.commit();

						

					}

					else{

						System.out.println("conn.rollback();2");

						conn.rollback();

					}

					

					ps=helper.createPreparedStatement("select user_id from  users  where username=?");

					ps.setString(1, username);

					rs=ps.executeQuery();

					int user_id=0;

					if(rs.next())

						user_id=rs.getInt("user_id");

					ps=helper.createPreparedStatement("update boss_customer set total_balance=ifnull(total_balance,0)+(?) where user_id=?");

					ps.setInt(1, count);

					ps.setInt(2, user_id);

					res+=ps.executeUpdate();

					if(res==3)

						conn.commit();

					else 

						conn.rollback();

				}

				

				

					

			}

			conn.commit();

			

		} catch (SQLException e)

		{

			try

			{

				conn.rollback();

			} catch (SQLException e1)

			{

				e1.printStackTrace();

			}

			e.printStackTrace();

		}

		helper.closeAll();

		return res==3;

	}