Question

我正在使用java进行Oracle Select for Update，它可以按时运行，有时会挂起会话并且无法删除锁定的会话（必须手动终止会话）这适用于大多数场景，但是当我将它部署在两个服务器（Web服务）并同时请求它们发生这种情况时，我无法理解它是否是我的代码的问题，我的代码

 public boolean checkJobStatus(long taskId)
{
    Connection con = null;
    PreparedStatement selectForUpdate = null;
    String lastJobStatus = null;
    boolean runNow = false;
    try
    {
        con = conPool.getConnection();
        con.setAutoCommit(false);
        selectForUpdate  = con.prepareStatement("SELECT LAST_JOB_STATUS FROM ADM_JOB WHERE TASK_ID = ? FOR UPDATE ");
        selectForUpdate.setLong(1, taskId);
        ResultSet resultSet = selectForUpdate.executeQuery();

        while(resultSet.next())
        {
            if (resultSet.getObject("LAST_JOB_STATUS") == null)
            {
                lastJobStatus = ScheduledJob.STATUS_FAILED;
            }
            else
            {
                lastJobStatus = resultSet.getString("LAST_JOB_STATUS");
            }
        }

     if(ScheduledJob.STATUS_RUNNING.equalsIgnoreCase(lastJobStatus) || ScheduledJob.STATUS_STARTED.equalsIgnoreCase(lastJobStatus))
     {
         runNow = false;
         // commit n update setting autocommit to true
         selectForUpdate = con.prepareStatement("UPDATE ADM_JOB SET LAST_JOB_STATUS =? WHERE TASK_ID = ?");
         selectForUpdate.setString(1, lastJobStatus);
         selectForUpdate.setLong(2, taskId);
         selectForUpdate.executeUpdate();
     }
     else
     {
         runNow =true;
         // commit n update setting autocommit to true
         selectForUpdate  = con.prepareStatement("UPDATE ADM_JOB SET LAST_JOB_STATUS =? WHERE TASK_ID = ?");
         selectForUpdate.setString(1, ScheduledJob.STATUS_STARTED);
         selectForUpdate.setLong(2, taskId);
         selectForUpdate.executeUpdate();

         con.commit();
         con.setAutoCommit(true);
     }

    } catch (SQLException e)
    {
        Logger.getLogger( "" ).log(Level.SEVERE, "Error in getting database connection", e);
        try
        {
            con.rollback();   // rolling back the row lock in case of a exception
        } catch (SQLException e1)
        {
            e1.printStackTrace();
        }
    }
    finally
    {
        DBUtility.close( selectForUpdate  );
        DBUtility.close( con );
    }


    return runNow;
}

Answer 1

提交仅在else分支中发生。如果这种情况没有发生，那么事务就不会被关闭，所以第二个线程会在select for update上永远挂起。

Oracle Select for update无法正常运行，有时会挂起

1 个答案: