POI操作office文档

office有两种标准：

1.（office open XML standars）OOXML，为office 2007以上版本的文档格式。后缀名为xlsx，docx，pptxMFC serialization API based file formats，等。可以使用

2.OLE2 compound document format，为office 97格式。后缀名为xls，docx，pptx等。

Excel (SS=HSSF+XSSF) 
Word (HWPF+XWPF) 
PowerPoint (HSLF+XSLF) 
OpenXML4J (OOXML) 
OLE2 Filesystem (POIFS) 
OLE2 Document Props (HPSF) 
Outlook (HSMF) 
Visio (HDGF) 
TNEF (HMEF) 
Publisher (HPBF) 

low level访问OLE2文档可以使用POIFS和HPSF，如果访问OOXML文档可以使用openxml4j。

high level访问对应关系：

xls：HSSF 

xlsx：XSSF

SS=HSSF+XSSF

doc：HWPF

docx：XWPF

ppt：HSLF

pptx：XSLF

下面的代码为两种格式转换。

FileInputStream fis = new FileInputStream(inputFile);
POIFSFileSystem fileSystem = new POIFSFileSystem(fis);
// Firstly, get an extractor for the Workbook
POIOLE2TextExtractor leTextExtractor = 
   ExtractorFactory.createExtractor(fileSystem);
// Then a List of extractors for any embedded Excel, Word, PowerPoint
// or Visio objects embedded into it.
POITextExtractor[] embeddedExtractors =
   ExtractorFactory.getEmbededDocsTextExtractors(oleTextExtractor);
for (POITextExtractor textExtractor : embeddedExtractors) {
   // If the embedded object was an Excel spreadsheet.
   if (textExtractor instanceof ExcelExtractor) {
      ExcelExtractor excelExtractor = (ExcelExtractor) textExtractor;
      System.out.println(excelExtractor.getText());
   }
   // A Word Document
   else if (textExtractor instanceof WordExtractor) {
      WordExtractor wordExtractor = (WordExtractor) textExtractor;
      String[] paragraphText = wordExtractor.getParagraphText();
      for (String paragraph : paragraphText) {
         System.out.println(paragraph);
      }
      // Display the document's header and footer text
      System.out.println("Footer text: " + wordExtractor.getFooterText());
      System.out.println("Header text: " + wordExtractor.getHeaderText());
   }
   // PowerPoint Presentation.
   else if (textExtractor instanceof PowerPointExtractor) {
      PowerPointExtractor powerPointExtractor =
         (PowerPointExtractor) textExtractor;
      System.out.println("Text: " + powerPointExtractor.getText());
      System.out.println("Notes: " + powerPointExtractor.getNotes());
   }
   // Visio Drawing
   else if (textExtractor instanceof VisioTextExtractor) {
      VisioTextExtractor visioTextExtractor = 
         (VisioTextExtractor) textExtractor;
      System.out.println("Text: " + visioTextExtractor.getText());
   }
}