解决POI读取Excel内存溢出的问题
https://blog.csdn.net/lishengbo/article/details/40711769
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();
- }
- }
- }
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