如何在Apache poi SXSSFWorkbook上添加自定义SheetDataWriter？

Question

    /**
 * Override this to translate (such as decrypt or expand) the file input stream
 * as it is being read from disk.
 * The default behavior is to to pass the stream through unmodified.
 *
 * @param fis  the stream to decorate
 * @return a decorated stream
 * @throws IOException
 * @see #decorateOutputStream(FileOutputStream)
 */
protected InputStream decorateInputStream(FileInputStream fis) throws IOException {
    return fis;
}

因为我想在设置compress：true时替换此方法

@Override
//GZIPInputStream default cache byte size is 512b
protected InputStream decorateInputStream(FileInputStream fis) throws IOException {
    return new GZIPInputStream(fis);
}

为什么我要换掉这个？因为我想弄清楚高速缓存大小是否是在高并发（apache jmeter：50个用户,6个循环,ramup 20）情况下减慢从POI-SXSSF-sheet？？？.gz到POI-SXSSF-template？？？.xlsx的写入速度的主要原因。但问题是在初始化SXSSFWorkbook时如何使用我自己的SheetDataWriter？

Answer 1

您是在问如何重写java中的方法吗？这似乎是一个很基本的问题。

您可以拥有自己的SXSSFWorkbook类，该类扩展默认的SXSSFWorkbook并覆盖受保护的SheetDataWriter createSheetDataWriter()。如果是压缩的临时文件，则可以返回扩展的GZipSheetDataWriter，它覆盖Protected InputStream decorateInputStream（FileInputStream fis)。

完整的工作示例：

import java.io.*;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.streaming.*;

import java.util.zip.GZIPInputStream;

class OverrideSXSSFWorkbook {

 public static void main(String[] args) throws Exception {

  try (
   SXSSFWorkbook workbook = new MySXSSFWorkbook(); FileOutputStream fileout = new FileOutputStream("Excel.xlsx") ) {

   workbook.setCompressTempFiles(true);

   Sheet sheet = workbook.createSheet();
   Row row;
   Cell cell;

   row = sheet.createRow(0);
   cell = row.createCell(0);
   cell.setCellValue("CellValue");
 
   workbook.write(fileout);
   workbook.close();
   workbook.dispose();

  }
 }
}

class MySXSSFWorkbook extends SXSSFWorkbook {

 @Override
 protected SheetDataWriter createSheetDataWriter() throws IOException {

  if(isCompressTempFiles()) {
   System.out.println("GZIPSheetDataWriter");
   //return new GZIPSheetDataWriter(getSharedStringSource());

   return new GZIPSheetDataWriter(getSharedStringSource()) {

    @Override
    protected InputStream decorateInputStream(FileInputStream fis) throws IOException {
     System.out.println("overridden decorateInputStream");
     return new GZIPInputStream(fis);
    }
   };

  }
  System.out.println("default SheetDataWriter");
  return new SheetDataWriter(getSharedStringSource());

 }
}