Question

我正在编写一个java应用程序，它从Oracle获取UTC时间，然后在一个表上查询一行是否与该时间匹配。如果没有结果，请再次使用UTC，依此类推。

但有时候时间会倒退或者需要花费1或2分钟的时间才能获得正确的时间。

这是UTC时间的日志：

15/03/2016 16:42:59 [INFO]  Time (UTC): 21:42:25 {1} 
15/03/2016 16:42:59 [INFO]  Time (UTC): 21:42:25 {2} 
15/03/2016 16:42:59 [INFO]  Time (UTC): 21:42:25 {3} 
15/03/2016 16:42:59 [INFO]  Time (UTC): 21:42:25 {4} 
15/03/2016 16:42:59 [INFO]  Time (UTC): 21:42:25 {5} 
15/03/2016 16:43:00 [INFO]  Time (UTC): 21:44:12 {6} 
15/03/2016 16:43:00 [INFO]  Time (UTC): 21:42:26 {7} 
15/03/2016 16:43:00 [INFO]  Time (UTC): 21:42:26 {8} 
15/03/2016 16:43:00 [INFO]  Time (UTC): 21:42:26 {9} 
15/03/2016 16:43:00 [INFO]  Time (UTC): 21:42:26 {10} 
15/03/2016 16:43:00 [INFO]  Time (UTC): 21:42:26 {11} 
15/03/2016 16:43:01 [INFO]  Time (UTC): 21:42:27 {12} 
15/03/2016 16:43:01 [INFO]  Time (UTC): 21:42:27 {13} 
15/03/2016 16:43:01 [INFO]  Time (UTC): 21:42:27 {14} 
15/03/2016 16:43:01 [INFO]  Time (UTC): 21:42:27 {15} 
15/03/2016 16:43:01 [INFO]  Time (UTC): 21:42:27 {16} 
15/03/2016 16:43:01 [INFO]  Time (UTC): 21:42:27 {17} 
15/03/2016 16:43:02 [INFO]  Time (UTC): 21:42:28 {18} 
15/03/2016 16:43:02 [INFO]  Time (UTC): 21:42:28 {19} 
15/03/2016 16:43:02 [INFO]  Time (UTC): 21:42:28 {20} 
15/03/2016 16:43:02 [INFO]  Time (UTC): 21:42:28 {21} 
15/03/2016 16:43:02 [INFO]  Time (UTC): 21:42:28 {22} 
15/03/2016 16:43:02 [INFO]  Time (UTC): 21:42:28 {23} 
15/03/2016 16:43:03 [INFO]  Time (UTC): 21:44:15 {24} 
15/03/2016 16:43:03 [INFO]  Time (UTC): 21:44:15 {25} 
15/03/2016 16:43:03 [INFO]  Time (UTC): 21:44:15 {26} 
15/03/2016 16:43:03 [INFO]  Time (UTC): 21:44:15 {27} 
15/03/2016 16:43:03 [INFO]  Time (UTC): 21:44:16 {28} 
15/03/2016 16:43:04 [INFO]  Time (UTC): 21:44:16 {29} 
15/03/2016 16:43:04 [INFO]  Time (UTC): 21:42:30 {30}

这是我的代码的一部分：

int arraycounter = 0;
int index = 0;

while (arraycounter = 0)
{       
    Connection con = null;
    Statement stmt = null;
    ResultSet rs = null;

    String utc_time = "";

    String querytime = "select to_char(sys_extract_utc(systimestamp),'HH24:MI:SS') from dual";

    try {
        Class.forName("oracle.jdbc.driver.OracleDriver");
        con = DriverManager.getConnection("jdbc:oracle:thin:"+ConnectionString);
        stmt = con.createStatement();
        rs = stmt.executeQuery(querytime);

        while(rs.next()) {
            utc_time = rs.getString(1);
        }

    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        try {
            rs.close();
            stmt.close();
            con.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    String query = "select * from table where to_char(date, 'hh24:mi:ss') = '"+utc_time+"'";

    index++;
    logger.info("Time (UTC): "+ utc_time +" {"+(index)+"}");

    try {
        Class.forName("oracle.jdbc.driver.OracleDriver");
        con = DriverManager.getConnection("jdbc:oracle:thin:"+ConnectionString);
        stmt = con.createStatement();
        rs = stmt.executeQuery(querytime);

        while( rs.next() ){             

        //save the result into an arraylist
        arraycounter++;

        }

    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        try {
            rs.close();
            stmt.close();
            con.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }   
}

为什么会这样？是否有更好的方式采用UTC时间？

Answer 1

我的Oracle数据库在RAC上，实例的时间不同步。我检查了进入实例并检查时间，然后进入另一个实例并检查时间。

要知道你可以在什么情况下运行：

select instance_name from v$instance;

为了连接到数据库的特定实例，您还可以在连接描述符中指定特定实例的INSTANCE_NAME。如果您具有Oracle Real Application Clusters配置，则此功能非常有用。例如，以下连接描述符指定与sales.us.acme.com关联的sales1的实例名称。

(DESCRIPTION= 
  (ADDRESS=(PROTOCOL=tcp)(HOST=sales-server)(PORT=1521))
  (CONNECT_DATA=
    (SERVICE_NAME=sales.us.acme.com)
    (INSTANCE_NAME=sales1)))

您可以在Oracle SQL Developer上将其指定为SID = sales1

为什么从Oracle获取的时间不一致？

1 个答案: