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本篇内容介绍了“Scala过度包装的平衡怎么理解”的有关知识,在实际案例的操作过程中,不少人都会遇到这样的困境,接下来就让小编带领大家学习一下如何处理这些情况吧!希望大家仔细阅读,能够学有所成!
最近,在阅读项目组的代码时,再次陷入了苦思:基于Java、Hibernate的商业应用开发确实陷入到了一个很痛苦的境界,这个问题实际上正在进行开发的大部分开发人员都不会感觉到,因为大家都觉得这就是正常的程序员生活。再说,几乎所有的框架都在力捧Hibernate这样的ORM工具能够极大的简化程序的开发,要不,你去使用使用 JDBC试试。
在Java中基于JDBC编程,确实有些汇编语言的感觉,摘抄一份实际项目的代码:
public void updateTerminalStatus(String timeout, String transtime) throws Exception { //更新超时终端的状态值(9为超时) String updateTerminal = "update T_Terminal set Status=9 " + " where TerminalID in (select TerminalID from T_Terminal where TO_CHAR(latestDate, 'yyyymmddHH24miss')<=? and (status=0 or status=2) ) "; //查询超时的终端信息,且该终端号在故障表中没有未处理的超时记录,(包含该终端号在故障表中没有超时记录的情况)。 String queryTimeOutTerm = "SELECT te.TerminalID FROM T_TERMINAL te WHERE te.status=9 "; String queryTerm = "SELECT terminalid FROM T_TROUBLELOG tr " + " WHERE tr.DeviceID='COMMMODULE' AND tr.TroubleID='CommTimeOut' " + " AND tr.SolveDate IS NULL GROUP BY terminalid "; //向故障表中添加一条新的故障记录。 String insertTrouble = "insert into T_TroubleLog (LogID, TerminalID, DeviceID, TroubleID, HappenDate) " + " values (?, ?, 'COMMMODULE', 'CommTimeOut', TO_DATE(?,'yyyymmddHH24miss')) "; //更新故障表中的终端超时记录,该终端号的状态已经不超时,则超时故障处理完毕。 String updateTrouble = "UPDATE T_TROUBLELOG tl SET tl.SolveDate=TO_DATE(?,'yyyymmddHH24miss') " + " WHERE terminalid IN" + " (SELECT tm.terminalid FROM T_TERMINAL tm,T_TROUBLELOG tl " + " WHERE tm.Status != 9 AND tm.TerminalID=tl.TerminalID )" + " AND tl.DeviceID='COMMMODULE' AND tl.TroubleID='CommTimeOut' AND tl.SolveDate IS NULL "; Connection conn = null; PreparedStatement pstmt = null; PreparedStatement pstmtInsert = null; ResultSet rs = null; List terlist = new ArrayList(); List noterlist = new ArrayList(); try { conn = transDataSource.getConnection(); conn.setAutoCommit(false); pstmt = conn.prepareStatement(updateTerminal); pstmt.setString(1, timeout); pstmt.executeUpdate(); pstmt.close(); pstmt = conn.prepareStatement(updateTrouble); pstmt.setString(1, transtime); pstmt.executeUpdate(); pstmt.close(); log.debug("更新完成"); //生成32位的随机ID,使用Hibernate中的UUID算法。 Properties props = new Properties(); props.setProperty("separator", ""); IdentifierGenerator gen = new UUIDHexGenerator(); ( (Configurable) gen ).configure(Hibernate.STRING, props, null); pstmtInsert = conn.prepareStatement(insertTrouble); pstmt = conn.prepareStatement(queryTerm); rs = pstmt.executeQuery(); while(rs.next()){ String termid = rs.getString(1); terlist.add(termid); } log.debug("查询终端号在故障表中没有未处理的超时记录完成"); rs.close(); rs = null; pstmt.close(); pstmt = null; pstmt = conn.prepareStatement(queryTimeOutTerm); rs = pstmt.executeQuery(); while (rs.next()) { String term = rs.getString(1); noterlist.add(term); } log.debug("查询超时的终端信息完成" + noterlist.size()); for(int j = 0; j < noterlist.size(); j++){ String terminalid = noterlist.get(j).toString(); if(terlist.contains(terminalid)){ continue; } pstmtInsert.setString(1, (String) gen.generate(null, null)); pstmtInsert.setString(2, terminalid); pstmtInsert.setString(3, transtime); pstmtInsert.addBatch(); } pstmtInsert.executeBatch(); conn.commit(); log.debug("向故障表中添加新的故障记录完成"); } catch (Exception ex) { try{ conn.rollback(); }catch (Exception e) { } throw ex; } finally { if (rs != null) { try { rs.close(); } catch (Exception ex) { } } if (pstmt != null) { try { pstmt.close(); } catch (Exception ex) { } } if (pstmtInsert != null) { try { pstmtInsert.close(); } catch (Exception ex) { } } if (conn != null) { try { conn.close(); } catch (Exception ex) { } } } }
这份代码长达120行,要去理解它还是得花一些时间的,如果使用 scala来写的话,可以怎么写呢?
implicit val conn: Connection = transDataSource.getConnection() transaction { update("""update T_Terminal set Status=9 where TerminalID in (select TerminalID from T_Terminal where TO_CHAR(latestDate, 'yyyymmddHH24miss')<= ? and (status=0 or status=2)) """, timeout); update("""UPDATE T_TROUBLELOG tl SET tl.SolveDate=TO_DATE(?,'yyyymmddHH24miss') WHERE terminalid IN (SELECT tm.terminalid FROM T_TERMINAL tm,T_TROUBLELOG tl WHERE tm.Status != 9 AND tm.TerminalID=tl.TerminalID ) AND tl.DeviceID='COMMMODULE' AND tl.TroubleID='CommTimeOut' AND tl.SolveDate IS NULL """, transtime); val terlist: List[String] = List() query("""SELECT terminalid FROM T_TROUBLELOG tr WHERE tr.DeviceID='COMMMODULE' AND tr.TroubleID='CommTimeOut' AND tr.SolveDate IS NULL GROUP BY terminalid """).foreach { (row) => terlist += row("terminalid") } log.debug("查询终端号在故障表中没有未处理的超时记录完成"); val noterlist: List[String] = List() query("SELECT te.TerminalID FROM T_TERMINAL te WHERE te.status=9").foreach { (row)=> noterlist += row("terminalid") } log.debug("查询超时的终端信息完成" + noterlist.size()); val psInsert = conn prepareStatement """insert into T_TroubleLog (LogID, TerminalID, DeviceID, TroubleID, HappenDate) values (?, ?, 'COMMMODULE', 'CommTimeOut', TO_DATE(?,'yyyymmddHH24miss'))""" for(val terminalId <- noterlist){ psInsert << uuid() << terminalid << transtime <<! } }
这是一个直译的版本,代码函数为34行,瘦身到25%左右。不仅代码行数更短,而且新的代码的可读性也更高得多。
最近一直在思考,我们对JDBC是否做了过度的包装?包括事务处理,DAO等从EJB1.0时代产生的设计模式,到后续的O-R-M框架,看上去代码是越发简洁,实际上已经远远的远离代码的本质。这种基于Scala的JDBC简单封装,即便于我,也还远不如原始的4GL的简洁,但相比传统的jdbc或者后续的orm、spring+dao等等,则要简化得多。
“Scala过度包装的平衡怎么理解”的内容就介绍到这里了,感谢大家的阅读。如果想了解更多行业相关的知识可以关注亿速云网站,小编将为大家输出更多高质量的实用文章!
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