java读取大容量excel之二（空格、空值问题）

　　最近在项目中发现，对于Excel2007（底层根本是xml） ,使用《java读取大容量excel之一》中的方式读取，若待读取的excel2007文件中某一列是空值，（注意，所谓的空值是什么都没有，而不是敲了空格后的形式，虽然敲了空格表面上看也没有值，但是有占位符，在底层xml中表现不一样），后出现自动忽略，若一个电子表格中有五列，而2,3列没值，则会读不到，这样会对于若程序后续对拿到的每一行数据进行判断，则会张冠李戴，容易出错，故研究了下.xlsx底层，如下：

　　

　　如图新建一个.xlsx文件，包含三行，首行是五个单元格合并为一个单元格，第二行为五个标题，全部有值，第三行仅仅第五列有值，注意，其他列每空格，即本文所述的空值，下面我们来看一下该excel文件的xml格式（ps：直接将.xlsx文件重命名为.zip文件打开即可）找到里面的xl>worksheets文件夹，打开sheet1.xml,如下：

　　

  1 <?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
  2 - <worksheet xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main" xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="x14ac" xmlns:x14ac="http://schemas.microsoft.com/office/spreadsheetml/2009/9/ac">
  3   <dimension ref="A1:E3" />
  4 - <sheetViews>
  5 - <sheetView tabSelected="1" workbookViewId="0">
  6   <selection activeCell="E3" sqref="E3" />
  7   </sheetView>
  8   </sheetViews>
  9   <sheetFormatPr defaultRowHeight="13.5" x14ac:dyDescent="0.15" />
 10 - <sheetData>
 11 - <row r="1" spans="1:5" x14ac:dyDescent="0.15">
 12 - <c r="A1" s="1" t="s">
 13   <v>5</v>
 14   </c>
 15   <c r="B1" s="1" />
 16   <c r="C1" s="1" />
 17   <c r="D1" s="1" />
 18   <c r="E1" s="1" />
 19   </row>
 20 - <row r="2" spans="1:5" x14ac:dyDescent="0.15">
 21 - <c r="A2" s="2" t="s">
 22   <v>0</v>
 23   </c>
 24 - <c r="B2" s="2" t="s">
 25   <v>1</v>
 26   </c>
 27 - <c r="C2" s="2" t="s">
 28   <v>2</v>
 29   </c>
 30 - <c r="D2" s="2" t="s">
 31   <v>3</v>
 32   </c>
 33 - <c r="E2" s="2" t="s">
 34   <v>4</v>
 35   </c>
 36   </row>
 37 - <row r="3" spans="1:5" x14ac:dyDescent="0.15">
 38 - <c r="E3" s="2">
 39   <v>10000</v>
 40   </c>
 41   </row>
 42   </sheetData>
 43 - <mergeCells count="1">
 44   <mergeCell ref="A1:E1" />
 45   </mergeCells>
 46   <phoneticPr fontId="1" type="noConversion" />
 47   <pageMargins left="0.7" right="0.7" top="0.75" bottom="0.75" header="0.3" footer="0.3" />
 48   <pageSetup paperSize="9" orientation="portrait" horizontalDpi="96" verticalDpi="96" r:id="rId1" />
 49   </worksheet>

sheet1.xml

　　下面我们仅仅是在刚刚的excel中E3单元格输入几个空格，则看一下xml

 <?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
 <worksheet xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main"
     xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships"
     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
     mc:Ignorable="x14ac"
     xmlns:x14ac="http://schemas.microsoft.com/office/spreadsheetml/2009/9/ac">
     <dimension ref="A1:E3" />
     <sheetViews>
         <sheetView tabSelected="1" workbookViewId="0">
             <selection activeCell="A3" sqref="A3" />
         </sheetView>
     </sheetViews>
     <sheetFormatPr defaultRowHeight="13.5" x14ac:dyDescent="0.15" />
     <sheetData>
         <row r="1" spans="1:5" x14ac:dyDescent="0.15">
             <c r="A1" s="2" t="s">
                 <v>5</v>
             </c>
             <c r="B1" s="2" />
             <c r="C1" s="2" />
             <c r="D1" s="2" />
             <c r="E1" s="2" />
         </row>
         <row r="2" spans="1:5" x14ac:dyDescent="0.15">
             <c r="A2" s="1" t="s">
                 <v>0</v>
             </c>
             <c r="B2" s="1" t="s">
                 <v>1</v>
             </c>
             <c r="C2" s="1" t="s">
                 <v>2</v>
             </c>
             <c r="D2" s="1" t="s">
                 <v>3</v>
             </c>
             <c r="E2" s="1" t="s">
                 <v>4</v>
             </c>
         </row>
         <row r="3" spans="1:5" x14ac:dyDescent="0.15">
             <c r="A3" t="s"><!-- 注意，这是在该单元格敲了几个空格后的，其xml底层存储即为有值，t="s",与什么也没输不一样！！！ -->
                 <v>6</v>
             </c>
             <c r="E3" s="1">
                 <v>10000</v>
             </c>
         </row>
     </sheetData>
     <mergeCells count="1">
         <mergeCell ref="A1:E1" />
     </mergeCells>
     <phoneticPr fontId="1" type="noConversion" />
     <pageMargins left="0.7" right="0.7" top="0.75" bottom="0.75"
         header="0.3" footer="0.3" />
     <pageSetup paperSize="9" orientation="portrait"
         horizontalDpi="96" verticalDpi="96" r:id="rId1" />
 </worksheet>

sheet2.xml

通过两个对比发现，.xlsx文件底层对于空值和空格是区别对待的，切不可同日而语，于是问题来的，对于我们要解析的excel2007中要是含有空值怎么办，（有空格不怕，会按照该列有值对待，只不过读出后是空，且顺序不会变化，基本没什么影响）下面是一种解决方案，仅供参考

 /* ====================================================================
    Licensed to the Apache Software Foundation (ASF) under one or more
    contributor license agreements.  See the NOTICE file distributed with
    this work for additional information regarding copyright ownership.
    The ASF licenses this file to You under the Apache License, Version 2.0
    (the "License"); you may not use this file except in compliance with
    the License.  You may obtain a copy of the License at

        http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.
 ==================================================================== */

 package com.speed.excel;

 import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.PrintStream;
 import java.util.ArrayList;
 import java.util.List;

 import javax.xml.parsers.ParserConfigurationException;
 import javax.xml.parsers.SAXParser;
 import javax.xml.parsers.SAXParserFactory;

 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.ContentHandler;
 import org.xml.sax.InputSource;
 import org.xml.sax.SAXException;
 import org.xml.sax.XMLReader;
 import org.xml.sax.helpers.DefaultHandler;

 /**
  * A rudimentary XLSX -> CSV processor modeled on the
  * POI sample program XLS2CSVmra by Nick Burch from the
  * package org.apache.poi.hssf.eventusermodel.examples.
  * Unlike the HSSF version, this one completely ignores
  * missing rows.
  * <p/>
  * Data sheets are read using a SAX parser to keep the
  * memory footprint relatively small, so this should be
  * able to read enormous workbooks.  The styles table and
  * the shared-string table must be kept in memory.  The
  * standard POI styles table class is used, but a custom
  * (read-only) class is used for the shared string table
  * because the standard POI SharedStringsTable grows very
  * quickly with the number of unique strings.
  * <p/>
  * Thanks to Eric Smith for a patch that fixes a problem
  * triggered by cells with multiple "t" elements, which is
  * how Excel represents different formats (e.g., one word
  * plain and one word bold).
  *
  * @author Chris Lott
  */
 public class XLSX2CSV {

     /**
      * 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,
     }

     /**
      * Derived from http://poi.apache.org/spreadsheet/how-to.html#xssf_sax_api
      * <p/>
      * Also see Standard ECMA-376, 1st edition, part 4, pages 1928ff, at
      * http://www.ecma-international.org/publications/standards/Ecma-376.htm
      * <p/>
      * 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;
         // 定义当前读到的列数，实际读取时会按照从0开始...
         private int thisColumn = -1;
         // 定义上一次读到的列序号
         private int lastColumnNumber = -1;
         // Gathers characters as they are seen.
         private StringBuffer value;
         // 定义存储每行内容的list
         private List<String> rowlist = new ArrayList<String>();
         // 定义当前读到的列与上一次读到的列中是否有空值（即该单元格什么也没有输入，连空格都不存在）默认为false
         private boolean flag = 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();
         }

         /*
            * (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));//获取当前读取的列数

                 // 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";
                         break;
                     case ERROR:
                         thisStr = "\"ERROR:" + value.toString() + '"';
                         break;
                     case FORMULA:
                         // A formula could result in a string value,
                         // so always add double-quote characters.
                         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() + '"';
                         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();
                         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;
                 }*/
                 // 以下是核心算法，在同一行内，若后一次比前一次读取的列序号相差大于1，证明中间没有读到值
                 // 按照.xlsx底层是xml描述文件原理，此时对应xml中"空值"情况
                 if(thisColumn - lastColumnNumber > 1){
                     flag = true ;
                 }
                 for (int i = lastColumnNumber; i < thisColumn; ++i){
                     if(flag && i > lastColumnNumber){
                         rowlist.add(i, "");
                     }
                 }

                 // Might be the empty string.
                 rowlist.add(thisColumn, thisStr.trim());

                 // Update column
                 if (thisColumn > -1){
                     lastColumnNumber = thisColumn;
                 }

             } else if ("row".equals(name)) {//读到一行末尾

                 // Print out any missing commas if needed
                 if (minColumns > 0) {
                     // Columns are 0 based
                     if (lastColumnNumber == -1) {
                         lastColumnNumber = 0;
                     }
                     for (int i = lastColumnNumber; i < (this.minColumnCount); i++) {
                         output.print("");
                     }
                 }
                 rowReader.getRows(sheetIndex, curRow, rowlist);
                 rowlist.clear();
                 curRow++;
                 flag = false ;
                 // We're onto a new row
                 output.println();
                 lastColumnNumber = -1;
             }
         }

         /**
          * 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;
         }

         public List<String> getRowlist() {
             return rowlist;
         }

         public void setRowlist(List<String> rowlist) {
             this.rowlist = rowlist;
         }

     }

     ///////////////////////////////////////

     private OPCPackage xlsxPackage;
     private int minColumns;
     private PrintStream output;

     // 当前行
      private int curRow = 0;

      private int sheetIndex = 0;

      private IRowReader rowReader;

      public void setRowReader(IRowReader rowReader) {
          this.rowReader = rowReader;
      }

     /**
      * 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
      * @param rowReader
      */
     public XLSX2CSV(OPCPackage pkg, PrintStream output, int minColumns,IRowReader rowReader) {
         this.xlsxPackage = pkg;
         this.output = output;
         this.minColumns = minColumns;
         this.rowReader = rowReader;
     }

     /**
      * Parses and shows the content of one sheet
      * using the specified styles and shared-strings tables.
      *
      * @param styles
      * @param strings
      * @param sheetInputStream
      */
     public void 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();
         ContentHandler handler = new MyXSSFSheetHandler(styles, strings, this.minColumns, this.output);
         sheetParser.setContentHandler(handler);
         sheetParser.parse(sheetSource);
     }

     /**
      * Initiates the processing of the XLS workbook file to CSV.
      *
      * @throws IOException
      * @throws OpenXML4JException
      * @throws ParserConfigurationException
      * @throws SAXException
      */
     public void process() throws Exception {
         InputStream stream = null ;
         try {
             ReadOnlySharedStringsTable strings = new ReadOnlySharedStringsTable(this.xlsxPackage);
             XSSFReader xssfReader = new XSSFReader(this.xlsxPackage);
             StylesTable styles = xssfReader.getStylesTable();
             XSSFReader.SheetIterator iter = (XSSFReader.SheetIterator) xssfReader.getSheetsData();
             while (iter.hasNext()) {
                 curRow = 0;
                 sheetIndex++;
                 stream = iter.next();
                 processSheet(styles, strings, stream);
                 stream.close();
             }
         } catch (IllegalArgumentException e) {
             e.printStackTrace();
             throw new IllegalArgumentException(e.getMessage());
         } catch (Exception e) {
             e.printStackTrace();
             throw new Exception("读取文件失败，此文件可能已损坏，请参照模板重新上传！");
         }finally{
             if(null != stream){
                 stream.close();
             }
         }
     }

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

         File xlsxFile = new File("C:\\Users\\liuyue\\Desktop\\test1.xlsx");
         if (!xlsxFile.exists()) {
             System.err.println("Not found or not a file: " + xlsxFile.getPath());
             return;
         }
         int minColumns = 6 ;
         // The package open is instantaneous, as it should be.
         OPCPackage p = OPCPackage.open(xlsxFile.getPath(), PackageAccess.READ);
         IRowReader reader = new RowReaderTest();
         XLSX2CSV xlsx2csv = new XLSX2CSV(p, System.out, minColumns ,reader);
         xlsx2csv.process();
     }

 }

XLSX2CSV