ExclToCsv

import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.openxml4j.util.ZipSecureFile;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import java.io.*;
import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

public class ExclToCsv {
    /**
     * 将excel表格转成csv格式
     * @param oldFilePath
     * @param newFilePath
     */
    public static void excelToCsv(String oldFilePath,String newFilePath){
        String buffer = "";
        Workbook wb =null;
        Sheet sheet = null;
        Row row = null;
        Row rowHead = null;
        List<Map<String,String>> list = null;
        String cellData = null;
        String filePath =oldFilePath ;

        wb = readExcel(filePath);
        if(wb != null){
            for (int i = 0; i < wb.getNumberOfSheets(); i++) {
                sheet = wb.getSheetAt(i);
                // 标题总列数
                rowHead = sheet.getRow(i);
                if (rowHead == null) {
                    continue;
                }
                //总列数colNum
                int colNum = rowHead.getPhysicalNumberOfCells();
                String[] keyArray = new String[colNum];
                Map<String, Object> map = new LinkedHashMap<>();

                //用来存放表中数据
                list = new ArrayList<Map<String,String>>();
                //获取第一个sheet
                sheet = wb.getSheetAt(i);
                //获取最大行数
                int rownum = sheet.getPhysicalNumberOfRows();
                //获取第一行
                row = sheet.getRow(0);
                //获取最大列数
                int colnum = row.getPhysicalNumberOfCells();
                for (int n = 0; n<rownum; n++) {
                    row = sheet.getRow(n);
                    for (int m = 0; m < colnum; m++) {

                        cellData =  getCellFormatValue(row.getCell(m)).toString();

                        buffer +=cellData;
                    }
                    buffer = buffer.substring(0, buffer.lastIndexOf(",")).toString();
                    buffer += "\n";

                }

                String savePath = newFilePath;
                File saveCSV = new File(savePath);
                try {
                    if(!saveCSV.exists()) {
                        saveCSV.createNewFile();
                    }
                    BufferedWriter writer = new BufferedWriter(new FileWriter(saveCSV));
                    writer.write(buffer);
                    writer.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }

            }

        }

    }


    //读取excel
    public static Workbook readExcel(String filePath){

        if(filePath==null){
            return null;
        }
        String extString = filePath.substring(filePath.lastIndexOf("."));
        InputStream is = null;
        ZipSecureFile.setMinInflateRatio(-1.0d);
        Workbook wb = null;
        try {
            is = new FileInputStream(filePath);
            if(".xls".equals(extString)){
                return wb = new HSSFWorkbook(is);
            }else if(".xlsx".equals(extString)){
                return wb = new XSSFWorkbook(is);
            }else{
                return wb = null;
            }

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return wb;
    }

    public static Object getCellFormatValue(Cell cell){
        Object cellValue = null;
        if(cell!=null){
            //判断cell类型
            switch(cell.getCellType()){
                case Cell.CELL_TYPE_NUMERIC:{
                    String cellva = getValue(cell);
                    cellValue = cellva.replaceAll("\n", " ") + ",";
                    break;
                }
                case Cell.CELL_TYPE_FORMULA:{
                    //判断cell是否为日期格式
                    if(DateUtil.isCellDateFormatted(cell)){
                        //转换为日期格式YYYY-mm-dd
                        cellValue = String.valueOf(cell.getDateCellValue()).replaceAll("\n", " ") + ",";
                    }else{
                        //数字
                        cellValue = String.valueOf(cell.getNumericCellValue()).replaceAll("\n", " ") + ",";
                    }
                    break;
                }
                case Cell.CELL_TYPE_STRING:{
                    cellValue = String.valueOf(cell.getRichStringCellValue()).replaceAll("\n", " ") + ",";
                    break;
                }
                default:
                    cellValue = "null"+ ",";
            }
        }else{
            cellValue = "null"+ ",";
        }
        return cellValue;
    }

    /**
     * 此方法为去掉转csv时数字等默认加上的小数点
     * 如果不需要刻意不调用此方法
     */
    public static  String getValue(Cell hssfCell) {
        if (hssfCell.getCellType() == hssfCell.CELL_TYPE_BOOLEAN) {
            // 返回布尔类型的值
            return String.valueOf(hssfCell.getBooleanCellValue());
        } else if (hssfCell.getCellType() == hssfCell.CELL_TYPE_NUMERIC) {
            // 返回数值类型的值
            Object inputValue = null;// 单元格值
            Long longVal = Math.round(hssfCell.getNumericCellValue());
            Double doubleVal = hssfCell.getNumericCellValue();
            if(Double.parseDouble(longVal + ".0") == doubleVal){   //判断是否含有小数位.0
                inputValue = longVal;
            }
            else{
                inputValue = doubleVal;
            }
            DecimalFormat df = new DecimalFormat("#");    //在此处更改小数点及位数，按自己需求选择；
            return String.valueOf(df.format(inputValue));      //返回String类型
        } else {
            // 返回字符串类型的值
            return String.valueOf(hssfCell.getStringCellValue());
        }
    }


//    public static void main(String[] args) throws Exception {
//        ExclToCsv.excelToCsv("D:\\1.8.0\\1617.xlsx","D:\\1.8.0\\test.csv");
//
//    }

}

import java.io.IOException;
import java.io.InputStream;
import java.io.PrintStream;

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.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;


public class XLSXTOCSV {

    /**
     * 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;

        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;

        /**
         * 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));

                // 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() + '"';
                        } 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;
                }
                for (int i = lastColumnNumber; i < thisColumn; ++i)
                    output.print(',');

                // Might be the empty string.
                output.print(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;
                    }
                    for (int i = lastColumnNumber; i < (this.minColumnCount); i++) {
                        output.print(',');
                    }
                }

                // 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;
        }

    }

    // /

    private OPCPackage xlsxPackage;
    private int minColumns;
    private PrintStream output;
    private final String OUTPUT_CHARSET = "GBK";

    /**
     * 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 XLSXTOCSV(OPCPackage pkg, PrintStream output, int minColumns) {
        this.xlsxPackage = pkg;
        this.output = output;
        this.minColumns = minColumns;
    }

    //TODO catch exceptions
    public XLSXTOCSV(String inputFilePath, String outputFilePath) throws Exception {
        xlsxPackage = OPCPackage.open(inputFilePath, PackageAccess.READ);
        output = new PrintStream(outputFilePath, OUTPUT_CHARSET);
        minColumns = -1;
    }

    /**
     * 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 IOException, OpenXML4JException,
            ParserConfigurationException, SAXException {

        ReadOnlySharedStringsTable strings = new ReadOnlySharedStringsTable(
                this.xlsxPackage);
        XSSFReader xssfReader = new XSSFReader(this.xlsxPackage);
        StylesTable styles = xssfReader.getStylesTable();
        XSSFReader.SheetIterator iter = (XSSFReader.SheetIterator) xssfReader
                .getSheetsData();
        int index = 0;
        while (iter.hasNext()) {
            InputStream stream = iter.next();
            String sheetName = iter.getSheetName();
            this.output.println();
            this.output.println(sheetName + " [index=" + index + "]:");
            processSheet(styles, strings, stream);
            stream.close();
            ++index;
        }
    }

//    public static void main(String[] args) throws Exception {
//        XLSXTOCSV xlsx2csv = new XLSXTOCSV("D:\\1.8.0\\1617.xlsx","D:\\1.8.0\\test.csv");
//        xlsx2csv.process();
//    }

}