解决POI读取Excel内存溢出的问题

Office软件一直是一个诲誉参半的软件，广大普通计算机用户用Office来满足日常办公需求，于是就产生了很多生产数据和文档，需要和企业单位的专用办公系统对接，而Office的解析工作一直是程序员非常头痛的问题，经常招致程序员的谩骂，也被誉为是微软最烂的发明之一。POI的诞生解决了Excel的解析难题（POI即“讨厌的电子表格”，确实很讨厌，我也很讨厌Excel），但如果用不好POI，也会导致程序出现一些BUG，例如内存溢出，假空行，公式等等问题。下面介绍一种解决POI读取Excel内存溢出的问题。

    POI读取Excel有两种模式，一种是用户模式，一种是SAX模式，将xlsx格式的文档转换成CVS格式后再进行处理用户模式相信大家都很清楚，也是POI常用的方式，用户模式API接口丰富，我们可以很容易的使用POI的API读取Excel，但用户模式消耗的内存很大，当遇到很多sheet、大数据网格、假空行、公式等问题时，很容易导致内存溢出。POI官方推荐解决内存溢出的方式使用CVS格式解析，我们不可能手工将Excel文件转换成CVS格式再上传，这样做太麻烦了，好再POI给出了xlsx转换CVS的例子，基于这个例子我进行了一下改造，即可解决用户模式读取Excel内存溢出的问题。下面附上代码:

/* ==================================================================== 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. ==================================================================== */

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CVS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); * * * @author 山人 */
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 * <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;
        private String[] record;
        private List<String[]> rows = new ArrayList<String[]>();
        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";
                    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();
                    // 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)// 判断是否空行
                    {
                        rows.add(record.clone());
                        isCellNull = false;
                        for (int i = 0; i < record.length; i++) {
                            record[i] = null;
                        }
                    }
                }
                lastColumnNumber = -1;
            }

        }

        public List<String[]> getRows() {
            return rows;
        }

        public void setRows(List<String[]> 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<String[]> 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 将 * * @throws IOException * @throws OpenXML4JException * @throws ParserConfigurationException * @throws SAXException */
    public List<String[]> process() throws IOException, OpenXML4JException,
            ParserConfigurationException, SAXException {

        ReadOnlySharedStringsTable strings = new ReadOnlySharedStringsTable(
                this.xlsxPackage);
        XSSFReader xssfReader = new XSSFReader(this.xlsxPackage);
        List<String[]> 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 */
    private static List<String[]> 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<String[]> list = xlsx2csv.process();
        p.close();
        return list;
    }

    public static void main(String[] args) throws Exception {
        List<String[]> list = XLSXCovertCSVReader
                .readerExcel(
                        "F:\\test.xlsx",
                        "Sheet1", 17);
        for (String[] record : list) {
            for (String cell : record) {
                System.out.print(cell + " ");
            }
            System.out.println();
        }
    }

}