Apache POI使用总结

Apache POI是Apache推出的Java操作Office文档的开源库，其中对Excel的支持最完整，所以一般公司涉及报表开发都会使用。之前工作中曾用过不到一年，当时用的是3.10版本，现在来看比较旧了，不知道和现在的版本差别大不大。

• POI对表格的操作都是从第0行、第0列开始。
• 读取表格的时候会读取到有数据的最后一行之后的空行，暂无解决办法，所以最好规定读取的行数。
• 读取xls格式使用HSSF，读取xlsx格式使用XSSF。
• 读取的xlsx数据大于10万时，最好使用下方提到的“POI读取EXCEL2007以上格式文件大量数据时的处理办法”。
• 写表格时，如果设置了合并单元格以及单元格边框，需要在合并单元格后再次设置边框。
• 在写入公式时，不要在单元格中直接写入“=XXXX”的公式，而是使用setCellFormula方法写入。
• POI读取EXCEL2007以上格式文件大量数据时的处理办法：
  (此段代码摘自网络不属于本人原创，本人使用过没有问题，使用的JDK版本是1.7)

  import java.io.IOException;
  import java.io.InputStream;
  import java.io.PrintStream;
  import java.text.SimpleDateFormat;
  import java.util.ArrayList;
  import java.util.Date;
  import java.util.List;
  
  import javax.xml.parsers.ParserConfigurationException;
  import javax.xml.parsers.SAXParser;
  import javax.xml.parsers.SAXParserFactory;
  
  import org.apache.poi.hssf.usermodel.HSSFDateUtil;
  import org.apache.poi.openxml4j.exceptions.OpenXML4JException;
  import org.apache.poi.openxml4j.opc.OPCPackage;
  import org.apache.poi.openxml4j.opc.PackageAccess;
  import org.apache.poi.ss.usermodel.BuiltinFormats;
  import org.apache.poi.ss.usermodel.DataFormatter;
  import org.apache.poi.xssf.eventusermodel.ReadOnlySharedStringsTable;
  import org.apache.poi.xssf.eventusermodel.XSSFReader;
  import org.apache.poi.xssf.model.StylesTable;
  import org.apache.poi.xssf.usermodel.XSSFCellStyle;
  import org.apache.poi.xssf.usermodel.XSSFRichTextString;
  import org.xml.sax.Attributes;
  import org.xml.sax.InputSource;
  import org.xml.sax.SAXException;
  import org.xml.sax.XMLReader;
  import org.xml.sax.helpers.DefaultHandler;
  
  /**
   * 使用CSV模式解决XLSX文件，可以有效解决用户模式内存溢出的问题。该模式是POI官方推荐的读取大数据的模式，在用户模式下，数据量较大、Sheet较多、或者是有很多无用的空行的情况，容易出现内存溢出，用户模式读取Excel的典型代码如下：
   * FileInputStream file=new FileInputStream("c:\\test.xlsx"); Workbook wb=new XSSFWorkbook(file);
   */
  public class XLSXCovertCSVReader {
      /**
       * The type of the data value is indicated by an attribute on the cell. The value is usually in a "v" element within the cell.
       */
      enum xssfDataType {
          BOOL, ERROR, FORMULA, INLINESTR, SSTINDEX, NUMBER,
      }
      
      /**
       * 使用xssf_sax_API处理Excel，请参考：http://poi.apache.org/spreadsheet/how-to.html#xssf_sax_api
       * 
       * Also see Standard ECMA-376, 1st edition, part 4, pages 1928ff, at http://www.ecma-international.org/publications/standards/Ecma-376.htm
       * 
       * A web-friendly version is http://openiso.org/Ecma/376/Part4
       */
      class MyXSSFSheetHandler extends DefaultHandler {
          /**
           * Table with styles
           */
          private StylesTable stylesTable;
          /**
           * Table with unique strings
           */
          private ReadOnlySharedStringsTable sharedStringsTable;
          /**
           * Destination for data
           */
          private final PrintStream output;
          /**
           * Number of columns to read starting with leftmost
           */
          private final int minColumnCount;
          // Set when V start element is seen
          private boolean vIsOpen;
          // Set when cell start element is seen;
          // used when cell close element is seen.
          private xssfDataType nextDataType;
          // Used to format numeric cell values.
          private short formatIndex;
          private String formatString;
          private final DataFormatter formatter;
          private int thisColumn = -1;
          // The last column printed to the output stream
          private int lastColumnNumber = -1;
          // Gathers characters as they are seen.
          private StringBuffer value;
          private String[] record;
          private List rows = new ArrayList();
          private boolean isCellNull = false;
          
          /**
           * Accepts objects needed while parsing.
           * 
           * @param styles
           *            Table of styles
           * @param strings
           *            Table of shared strings
           * @param cols
           *            Minimum number of columns to show
           * @param target
           *            Sink for output
           */
          public MyXSSFSheetHandler(StylesTable styles, ReadOnlySharedStringsTable strings, int cols, PrintStream target) {
              this.stylesTable = styles;
              this.sharedStringsTable = strings;
              this.minColumnCount = cols;
              this.output = target;
              this.value = new StringBuffer();
              this.nextDataType = xssfDataType.NUMBER;
              this.formatter = new DataFormatter();
              record = new String[this.minColumnCount];
              rows.clear();// 每次读取都清空行集合
          }
          
          /*
           * (non-Javadoc)
           * 
           * @see org.xml.sax.helpers.DefaultHandler#startElement(java.lang.String, java.lang.String, java.lang.String, org.xml.sax.Attributes)
           */
          public void startElement(String uri, String localName, String name, Attributes attributes) throws SAXException {
              if ("inlineStr".equals(name) || "v".equals(name)) {
                  vIsOpen = true;
                  // Clear contents cache
                  value.setLength(0);
              }
              // c => cell
              else if ("c".equals(name)) {
                  // Get the cell reference
                  String r = attributes.getValue("r");
                  int firstDigit = -1;
                  for (int c = 0; c < r.length(); ++c) {
                      if (Character.isDigit(r.charAt(c))) {
                          firstDigit = c;
                          break;
                      }
                  }
                  thisColumn = nameToColumn(r.substring(0, firstDigit));
                  // Set up defaults.
                  this.nextDataType = xssfDataType.NUMBER;
                  this.formatIndex = -1;
                  this.formatString = null;
                  String cellType = attributes.getValue("t");
                  String cellStyleStr = attributes.getValue("s");
                  if ("b".equals(cellType))
                      nextDataType = xssfDataType.BOOL;
                  else if ("e".equals(cellType))
                      nextDataType = xssfDataType.ERROR;
                  else if ("inlineStr".equals(cellType))
                      nextDataType = xssfDataType.INLINESTR;
                  else if ("s".equals(cellType))
                      nextDataType = xssfDataType.SSTINDEX;
                  else if ("str".equals(cellType))
                      nextDataType = xssfDataType.FORMULA;
                  else if (cellStyleStr != null) {
                      // It's a number, but almost certainly one with a special style or format
                      int styleIndex = Integer.parseInt(cellStyleStr);
                      XSSFCellStyle style = stylesTable.getStyleAt(styleIndex);
                      this.formatIndex = style.getDataFormat();
                      this.formatString = style.getDataFormatString();
                      if (this.formatString == null)
                          this.formatString = BuiltinFormats.getBuiltinFormat(this.formatIndex);
                  }
              }
          }
          
          /*
           * (non-Javadoc)
           * 
           * @see org.xml.sax.helpers.DefaultHandler#endElement(java.lang.String, java.lang.String, java.lang.String)
           */
          public void endElement(String uri, String localName, String name) throws SAXException {
              String thisStr = null;
              // v => contents of a cell
              if ("v".equals(name)) {
                  // Process the value contents as required.
                  // Do now, as characters() may be called more than once
                  switch (nextDataType) {
                  case BOOL:
                      //char first = value.charAt(0);
                      //thisStr = first == '0' ? "FALSE" : "TRUE";
                      thisStr = value.toString();
                      break;
                  case ERROR:
                      //thisStr = "\"ERROR:" + value.toString() + '"';
                      thisStr = value.toString();
                      break;
                  case FORMULA:
                      // A formula could result in a string value,
                      // so always add double-quote characters.
                      // thisStr = '"' + value.toString() + '"';
                      thisStr = value.toString();
                      break;
                  case INLINESTR:
                      // TODO: have seen an example of this, so it's untested.
                      XSSFRichTextString rtsi = new XSSFRichTextString(value.toString());
                      //thisStr = '"' + rtsi.toString() + '"';
                      thisStr = rtsi.toString();
                      break;
                  case SSTINDEX:
                      String sstIndex = value.toString();
                      try {
                          int idx = Integer.parseInt(sstIndex);
                          XSSFRichTextString rtss = new XSSFRichTextString(sharedStringsTable.getEntryAt(idx));
                          //thisStr = '"' + rtss.toString() + '"';
                          thisStr = rtss.toString();
                      } catch (NumberFormatException ex) {
                          output.println("Failed to parse SST index '" + sstIndex + "': " + ex.toString());
                      }
                      break;
                  case NUMBER:
                      String n = value.toString();
                      // 判断是否是日期格式
                      if (HSSFDateUtil.isADateFormat(this.formatIndex, n)) {
                          Double d = Double.parseDouble(n);
                          Date date = HSSFDateUtil.getJavaDate(d);
                          thisStr = formateDateToString(date);
                      } else if (this.formatString != null)
                          thisStr = formatter.formatRawCellContents(Double.parseDouble(n), this.formatIndex, this.formatString);
                      else
                          thisStr = n;
                      break;
                  default:
                      thisStr = "(TODO: Unexpected type: " + nextDataType + ")";
                      break;
                  }
                  // Output after we've seen the string contents
                  // Emit commas for any fields that were missing on this row
                  if (lastColumnNumber == -1) {
                      lastColumnNumber = 0;
                  }
                  // 判断单元格的值是否为空
                  if (thisStr == null || "".equals(isCellNull)) {
                      isCellNull = true;// 设置单元格是否为空值
                  }
                  record[thisColumn] = thisStr;
                  // Update column
                  if (thisColumn > -1)
                      lastColumnNumber = thisColumn;
              } else if ("row".equals(name)) {
                  // Print out any missing commas if needed
                  if (minColumns > 0) {
                      // Columns are 0 based
                      if (lastColumnNumber == -1) {
                          lastColumnNumber = 0;
                      }
                      if (isCellNull == false && record[0] == null && record[1] == null && record[2] == null) {
                      } else {
                          rows.add(record.clone());
                      }
                  }
                  lastColumnNumber = -1;
              }
          }
          
          public List getRows() {
              return rows;
          }
          
          public void setRows(List rows) {
              this.rows = rows;
          }
  
          /**
           * Captures characters only if a suitable element is open. Originally was just "v"; extended for inlineStr also.
           */
          public void characters(char[] ch, int start, int length) throws SAXException {
              if (vIsOpen)
                  value.append(ch, start, length);
          }
  
          /**
           * Converts an Excel column name like "C" to a zero-based index.
           * 
           * @param name
           * @return Index corresponding to the specified name
           */
          private int nameToColumn(String name) {
              int column = -1;
              for (int i = 0; i < name.length(); ++i) {
                  int c = name.charAt(i);
                  column = (column + 1) * 26 + c - 'A';
              }
              return column;
          }
  
          private String formateDateToString(Date date) {
              SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");// 格式化日期
              return sdf.format(date);
          }
      }
  
      private OPCPackage xlsxPackage;
      private int minColumns;
      private PrintStream output;
      private String sheetName;
  
      /**
       * Creates a new XLSX -> CSV converter
       * 
       * @param pkg
       *            The XLSX package to process
       * @param output
       *            The PrintStream to output the CSV to
       * @param minColumns
       *            The minimum number of columns to output, or -1 for no minimum
       */
      public XLSXCovertCSVReader(OPCPackage pkg, PrintStream output, String sheetName, int minColumns) {
          this.xlsxPackage = pkg;
          this.output = output;
          this.minColumns = minColumns;
          this.sheetName = sheetName;
      }
  
      /**
       * Parses and shows the content of one sheet using the specified styles and shared-strings tables.
       * 
       * @param styles
       * @param strings
       * @param sheetInputStream
       */
      public List processSheet(StylesTable styles, ReadOnlySharedStringsTable strings, InputStream sheetInputStream) throws IOException,
              ParserConfigurationException, SAXException {
          InputSource sheetSource = new InputSource(sheetInputStream);
          SAXParserFactory saxFactory = SAXParserFactory.newInstance();
          SAXParser saxParser = saxFactory.newSAXParser();
          XMLReader sheetParser = saxParser.getXMLReader();
          MyXSSFSheetHandler handler = new MyXSSFSheetHandler(styles, strings, this.minColumns, this.output);
          sheetParser.setContentHandler(handler);
          sheetParser.parse(sheetSource);
          return handler.getRows();
      }
  
      /**
       * 初始化这个处理程序
       * 
       * @throws IOException
       * @throws OpenXML4JException
       * @throws ParserConfigurationException
       * @throws SAXException
       */
      public List process() throws IOException, OpenXML4JException, ParserConfigurationException, SAXException {
          ReadOnlySharedStringsTable strings = new ReadOnlySharedStringsTable(this.xlsxPackage);
          XSSFReader xssfReader = new XSSFReader(this.xlsxPackage);
          List list = null;
          StylesTable styles = xssfReader.getStylesTable();
          XSSFReader.SheetIterator iter = (XSSFReader.SheetIterator) xssfReader.getSheetsData();
          int index = 0;
          while (iter.hasNext()) {
              InputStream stream = iter.next();
              String sheetNameTemp = iter.getSheetName();
              if (this.sheetName.equals(sheetNameTemp)) {
                  list = processSheet(styles, strings, stream);
                  stream.close();
                  ++index;
              }
          }
          return list;
      }
  
      /**
       * 读取Excel
       * 
       * @param path
       *            文件路径
       * @param sheetName
       *            sheet名称
       * @param minColumns
       *            列总数
       * @return
       * @throws SAXException
       * @throws ParserConfigurationException
       * @throws OpenXML4JException
       * @throws IOException
       */
      public static List readerExcel(String path, String sheetName, int minColumns) throws IOException, OpenXML4JException,
              ParserConfigurationException, SAXException {
          OPCPackage p = OPCPackage.open(path, PackageAccess.READ);
          XLSXCovertCSVReader xlsx2csv = new XLSXCovertCSVReader(p, System.out, sheetName, minColumns);
          List list = xlsx2csv.process();
          p.close();
          return list;
      }
  
      public static void main(String[] args) throws Exception {
          List list = XLSXCovertCSVReader.readerExcel("C:/test.xlsx", "Sheet1", 14);
          for (String[] record : list) {
              for (String cell : record) {
                  System.out.print(cell + "  ");
              }
              System.out.println();
          }
      }
  }