Apache POI总结原

wuweixiang

发布于 2018-08-14 11:37:29

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发布于 2018-08-14 11:37:29

文章被收录于专栏：吴伟祥吴伟祥

工作簿、工作表、单元格、行、列的概念

Apache POI 是用Java编写的免费开源的跨平台的 Java API，Apache POI提供API给Java程式对Microsoft Office格式档案读和写的功能。POI为“Poor Obfuscation Implementation”的首字母缩写，意为“可怜的模糊实现”。

Excel与POI对应关系:

表关系

Excel	POI
Sheet1表	0sheet
Sheet2表	1sheet
Sheet3表	2sheet
...	...

行关系

Excel	POI
1行	row0
2行	row1
3行	row2
...	...

列关系

Excel	POI
1列	cell0
2列	cell1
3列	cell2
...

Creating Cells

//workbook-->sheet-->row-->cell

Workbook wb = new HSSFWorkbook();
//Workbook wb = new XSSFWorkbook();
CreationHelper createHelper = wb.getCreationHelper();
Sheet sheet = wb.createSheet("new sheet");

// Create a row and put some cells in it. Rows are 0 based.
Row row = sheet.createRow((short)0);
// Create a cell and put a value in it.
Cell cell = row.createCell(0);
cell.setCellValue(1);

// Or do it on one line.
row.createCell(1).setCellValue(1.2);
row.createCell(2).setCellValue(
        createHelper.createRichTextString("This is a string"));
row.createCell(3).setCellValue(true);

// Write the output to a file
FileOutputStream fileOut = new FileOutputStream("workbook.xls");
wb.write(fileOut);
fileOut.close();

Files vs InputStreams

When opening a workbook, either a .xls HSSFWorkbook, or a .xlsx XSSFWorkbook, the Workbook can be loaded from either a File or an InputStream. Using a File object allows for lower memory consumption, while an InputStream requires more memory as it has to buffer the whole file.

If using WorkbookFactory, it's very easy to use one or the other:

// Use a file
  Workbook wb = WorkbookFactory.create(new File("MyExcel.xls"));

  // Use an InputStream, needs more memory
  Workbook wb = WorkbookFactory.create(new FileInputStream("MyExcel.xlsx"));

If using HSSFWorkbook or XSSFWorkbook directly, you should generally go through NPOIFSFileSystem or OPCPackage, to have full control of the lifecycle (including closing the file when done):

// HSSFWorkbook, File
  NPOIFSFileSystem fs = new NPOIFSFileSystem(new File("file.xls"));
  HSSFWorkbook wb = new HSSFWorkbook(fs.getRoot(), true);
  ....
  fs.close();

  // HSSFWorkbook, InputStream, needs more memory
  NPOIFSFileSystem fs = new NPOIFSFileSystem(myInputStream);
  HSSFWorkbook wb = new HSSFWorkbook(fs.getRoot(), true);

  // XSSFWorkbook, File
  OPCPackage pkg = OPCPackage.open(new File("file.xlsx"));
  XSSFWorkbook wb = new XSSFWorkbook(pkg);
  ....
  pkg.close();

  // XSSFWorkbook, InputStream, needs more memory
  OPCPackage pkg = OPCPackage.open(myInputStream);
  XSSFWorkbook wb = new XSSFWorkbook(pkg);
  ....
  pkg.close();