锁定MYSQL表

	public static int getId(String table,String field){
		int id=0;
		try{
			Connection conn = DBPool.getConnection();
			Statement stmt = conn.createStatement();
			stmt.execute("lock tables "+table+" read ");
			ResultSet rs=stmt.executeQuery("select "+field+" from "+table+" order by "+field+" desc limit 1");
			

			if(rs.next())
				id = rs.getInt(1)+1;
			rs.close();
			stmt.execute("unlock tables");
			stmt.close();
			conn.close();
		}catch(Exception e)
		{
			e.printStackTrace();
		}
		return id;
	}