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如何指示CSVPrinter在添加记录时不写入标题行?

apache-commons-csv java-7

Agi Hammerthief · 技术社区 · 6 年前

ControllerID,Event,Number,ReaderID,Timestamp,TransactionID, CSVPrinter 我正在使用将一行插入到同一个CSV中。但是,当打印机添加一个记录时,它会在新记录之前添加一个标题行,如下所示:

0,1,2688229830,3,2018-09-03 13:54,63
ControllerID,Event,Number,ReaderID,Timestamp,TransactionID
0,1,4900920,2,2018-09-03,15:15,176492

问题代码如下所示:

/* Add an entry to the TransactionLog CSV */
private static boolean logTransaction (
  int cid, int rid, boolean freeExit, long tsMS, long accNum, String reason
) {
  boolean added = false;
  int evt = freeExit ? 8 : 1;
  File transactLog = new File(Locations.getDatabaseDir(), "TransactLog.csv"),

  CSVFormat shortFormat = CSVFormat.DEFAULT.withQuote(null)
    .withAllowMissingColumnNames(true)/*.withTrailingDelimiter(true)*/
    .withHeader(Transaction.getHeader(false));
  // Attempt to read the last transaction ID and add 1 to it, to be used as ID of new transaction
  try (
    CSVParser shortParser = new CSVParser(new FileReader(transactLog), shortFormat);
    CSVPrinter shortWriter = new CSVPrinter(new FileWriter(transactLog, true), shortFormat);
  ) {
    // read in all the current records, getting the transactionID of the last record
    List<CSVRecord> shortRecords = shortParser.getRecords();
    int newTransId = 1;
    if (!shortRecords.isEmpty()) {
      CSVRecord last = shortRecords.get(shortRecords.size() - 1);
      String lastTransactionId = last.get("TransactionID");
      // add one to last transaction ID
      try {
        newTransId = Integer.parseInt(lastTransactionId) + 1;
      } catch (IllegalArgumentException IAEx) {
        newTransId = shortRecords.size() + 1;
        LOGGER.warn("Failed to determine last transaction ID from CSV ("
          + lastTransactionId + "); setting to recordCount (" + newTransId + ") ..."
        );
      }
    }
    // write the new transaction record
    Transaction t = new Transaction(cid, evt, accNum, rid, tsMS, newTransId, reason);
    List<String> tValues = t.asList(false), fValues = t.asList(true);
    shortWriter.printRecord(tValues);
    shortWriter.flush();
    added = true;
  } catch (IOException IOEx) {
    added = false;
    LOGGER.error(Util.getErrorTrace(
      "Failed to write transaction to \"" + transactLog.getAbsolutePath() + "\" CSV", IOEx
    ));
  }

  return added;
}

事务POJO的代码被省略,因为它与问题无关。

如何防止 CSV打印机

1 回复 | 直到 6 年前

Agi Hammerthief 6 年前

为了不输出标题行,需要添加 .withSkipHeaderRecord(true) CSVFormat CSVPrinter ,如下所示:

CSVFormat skipFormat = CSVFormat.DEFAULT.withQuote(null)
  .withAllowMissingColumnNames(true).withTrailingDelimiter(true)
  .withHeader(Transaction.getHeader(false))
  .withSkipHeaderRecord(true).withIgnoreEmptyLines(true);

呼叫 .withIgnoreEmptyLines(true) 是可选的。为了不保留空行/空行,包含了它。

如果要将头行作为文件中的第一行输出,则可以在创建头行时进行更改 .withSkipHeaderRecord(真) 到 .withSkipHeaderRecord(csvFile.exists()) . 这是因为文件在创建之前并不存在,但在下一次写入记录时确实存在。