EasyExcel使用详解

• 1、EasyExcel简单介绍
• • 64M内存20秒读取75M(46W行25列)的Excel（3.0.2+版本）
• 2、EasyExcel和POI数据处理能力对比
• 3、使用EasyExcel读写Excel、web上传/下载
• • 3.1、写EXCEL
  • 3.2、读EXCEL
  • 3.3、web上传、下载
• 4、EasyExcel源码解读
• 5、总结

1、EasyExcel简单介绍

官方介绍：Java解析、生成Excel比较有名的框架有Apache poi、jxl。但他们都存在一个严重的问题就是非常的耗内存，poi有一套SAX模式的API可以一定程度的解决一些内存溢出的问题，但POI还是有一些缺陷，比如07版Excel解压缩以及解压后存储都是在内存中完成的，内存消耗依然很大。easyexcel重写了poi对07版Excel的解析，一个3M的excel用POI sax解析依然需要100M左右内存，改用easyexcel可以降低到几M，并且再大的excel也不会出现内存溢出；03版依赖POI的sax模式，在上层做了模型转换的封装，让使用者更加简单方便。
普及一个知识点：读写速度 cpu>内存>磁盘

64M内存20秒读取75M(46W行25列)的Excel（3.0.2+版本）

当然还有极速模式能更快，但是内存占用会在100M多一点 img

2、EasyExcel和POI数据处理能力对比

poi

阿里easyExcel

下面是poi和easyexcel解析excel的过程

3、使用EasyExcel读写Excel、web上传/下载

3.1、写EXCEL

	/*** 最简单的写* 
1. 创建excel对应的实体对象 参照{@link com.alibaba.easyexcel.test.demo.write.DemoData}* 
2. 直接写即可*/@Testpublic void simpleWrite() {//时间long begin = System.currentTimeMillis();// 注意 simpleWrite在数据量不大的情况下可以使用（5000以内，具体也要看实际情况），数据量大参照 重复多次写入// 写法1 JDK8+// since: 3.0.0-beta1String fileName = PATH + "simpleWrite" + System.currentTimeMillis() + ".xlsx";// 这里 需要指定写用哪个class去写，然后写到第一个sheet，名字为模板 然后文件流会自动关闭// 如果这里想使用03 则 传入excelType参数即可EasyExcel.write(fileName, DemoData.class).sheet("模板").doWrite(() -> {// 分页查询数据return data();});long end = System.currentTimeMillis();System.out.println("耗时："+(end-begin));}

优点：数量无限制（单sheet最大支持1048576行），速度比POI的SXSSF方式快

多种写法

@Testpublic void simpleWrite() {// 注意 simpleWrite在数据量不大的情况下可以使用（5000以内，具体也要看实际情况），数据量大参照 重复多次写入// 写法1 JDK8+// since: 3.0.0-beta1String fileName = TestFileUtil.getPath() + "simpleWrite" + System.currentTimeMillis() + ".xlsx";// 这里 需要指定写用哪个class去写，然后写到第一个sheet，名字为模板 然后文件流会自动关闭// 如果这里想使用03 则 传入excelType参数即可EasyExcel.write(fileName, DemoData.class).sheet("模板").doWrite(() -> {// 分页查询数据return data();});// 写法2fileName = TestFileUtil.getPath() + "simpleWrite" + System.currentTimeMillis() + ".xlsx";// 这里 需要指定写用哪个class去写，然后写到第一个sheet，名字为模板 然后文件流会自动关闭// 如果这里想使用03 则 传入excelType参数即可EasyExcel.write(fileName, DemoData.class).sheet("模板").doWrite(data());// 写法3fileName = TestFileUtil.getPath() + "simpleWrite" + System.currentTimeMillis() + ".xlsx";// 这里 需要指定写用哪个class去写try (ExcelWriter excelWriter = EasyExcel.write(fileName, DemoData.class).build()) {WriteSheet writeSheet = EasyExcel.writerSheet("模板").build();excelWriter.write(data(), writeSheet);}}

3.2、读EXCEL

多种读法

	/*** 最简单的读* 
* 1. 创建excel对应的实体对象 参照{@link DemoData}* 
* 2. 由于默认一行行的读取excel，所以需要创建excel一行一行的回调监听器，参照{@link DemoDataListener}* 
* 3. 直接读即可*/@Testpublic void simpleRead() {// 写法1：JDK8+ ,不用额外写一个DemoDataListener// since: 3.0.0-beta1String fileName = TestFileUtil.getPath() + "demo" + File.separator + "demo.xlsx";// 这里 需要指定读用哪个class去读，然后读取第一个sheet 文件流会自动关闭// 这里每次会读取100条数据 然后返回过来 直接调用使用数据就行EasyExcel.read(fileName, DemoData.class, new PageReadListener(dataList -> {for (DemoData demoData : dataList) {log.info("读取到一条数据{}", JSON.toJSONString(demoData));}})).sheet().doRead();// 写法2：// 匿名内部类 不用额外写一个DemoDataListenerfileName = TestFileUtil.getPath() + "demo" + File.separator + "demo.xlsx";// 这里 需要指定读用哪个class去读，然后读取第一个sheet 文件流会自动关闭EasyExcel.read(fileName, DemoData.class, new ReadListener() {/*** 单次缓存的数据量*/public static final int BATCH_COUNT = 100;/***临时存储*/private List cachedDataList = ListUtils.newArrayListWithExpectedSize(BATCH_COUNT);@Overridepublic void invoke(DemoData data, AnalysisContext context) {cachedDataList.add(data);if (cachedDataList.size() >= BATCH_COUNT) {saveData();// 存储完成清理 listcachedDataList = ListUtils.newArrayListWithExpectedSize(BATCH_COUNT);}}@Overridepublic void doAfterAllAnalysed(AnalysisContext context) {saveData();}/*** 加上存储数据库*/private void saveData() {log.info("{}条数据，开始存储数据库！", cachedDataList.size());log.info("存储数据库成功！");}}).sheet().doRead();// 有个很重要的点 DemoDataListener 不能被spring管理，要每次读取excel都要new,然后里面用到spring可以构造方法传进去// 写法3：fileName = TestFileUtil.getPath() + "demo" + File.separator + "demo.xlsx";// 这里 需要指定读用哪个class去读，然后读取第一个sheet 文件流会自动关闭EasyExcel.read(fileName, DemoData.class, new DemoDataListener()).sheet().doRead();// 写法4fileName = TestFileUtil.getPath() + "demo" + File.separator + "demo.xlsx";// 一个文件一个readertry (ExcelReader excelReader = EasyExcel.read(fileName, DemoData.class, new DemoDataListener()).build()) {// 构建一个sheet 这里可以指定名字或者noReadSheet readSheet = EasyExcel.readSheet(0).build();// 读取一个sheetexcelReader.read(readSheet);}}

3.3、web上传、下载

	/*** 文件下载（失败了会返回一个有部分数据的Excel）* 
* 1. 创建excel对应的实体对象 参照{@link DownloadData}* 
* 2. 设置返回的 参数* 
* 3. 直接写，这里注意，finish的时候会自动关闭OutputStream,当然你外面再关闭流问题不大*/@GetMapping("download")public void download(HttpServletResponse response) throws IOException {// 这里注意 有同学反应使用swagger 会导致各种问题，请直接用浏览器或者用postmanresponse.setContentType("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");response.setCharacterEncoding("utf-8");// 这里URLEncoder.encode可以防止中文乱码 当然和easyexcel没有关系String fileName = URLEncoder.encode("测试", "UTF-8").replaceAll("\\+", "%20");response.setHeader("Content-disposition", "attachment;filename*=utf-8''" + fileName + ".xlsx");EasyExcel.write(response.getOutputStream(), DownloadData.class).sheet("模板").doWrite(data());}/*** 文件上传* 
1. 创建excel对应的实体对象 参照{@link UploadData}* 
2. 由于默认一行行的读取excel，所以需要创建excel一行一行的回调监听器，参照{@link UploadDataListener}* 
3. 直接读即可*/@PostMapping("upload")@ResponseBodypublic String upload(MultipartFile file) throws IOException {EasyExcel.read(file.getInputStream(), UploadData.class, new UploadDataListener(uploadDAO)).sheet().doRead();return "success";}

4、EasyExcel源码解读

1、入口（有不同写法，这里只看这一种）

2、进入EasyExcel类，发现它是继承了EasyExcelFactory类，EasyExcel自动拥有EasyExcelFactory父类的所有方法。

3、进入.read方法，需要传入三个参数(文件路径，表头映射类，read监听器)
首先调用new ExcelReaderBuilder()方法，初始化ReadWorkbook对象
设置完readWorkbook属性后调，返回excelReaderBuilder对象

4、这里又个传入的参数是read监听器，进入其内部看一下，我们自定义了PageReadListener实现了ReadListener，我们来看一下ReadListener接口源码

public interface ReadListener extends Listener {/*** All listeners receive this method when any one Listener does an error report. If an exception is thrown here, the* entire read will terminate.* 当任何一个侦听器执行错误报告时，所有侦听器都会收到此方法。如果在此处引发异常** @param exception* @param context* @throws Exception*/default void onException(Exception exception, AnalysisContext context) throws Exception {throw exception;}/*** When analysis one head row trigger invoke function.* 分析时 第一行表头触发器调用函数。** @param headMap* @param context*/default void invokeHead(Map> headMap, AnalysisContext context) {}/*** When analysis one row trigger invoke function.* 分析时，一行触发器调用函数。** @param data    one row value. Is is same as {@link AnalysisContext#readRowHolder()}* @param context analysis context*/void invoke(T data, AnalysisContext context);/*** The current method is called when extra information is returned* 返回额外信息时调用当前方法** @param extra   extra information* @param context analysis context*/default void extra(CellExtra extra, AnalysisContext context) {}/*** if have something to do after all analysis* 如果分析后有什么事要做** @param context*/void doAfterAllAnalysed(AnalysisContext context);/*** Verify that there is another piece of data.You can stop the read by returning false* 验证是否存在另一条数据。您可以通过返回false来停止读取** @param context* @return*/default boolean hasNext(AnalysisContext context) {return true;}
}

我们在PageReadListener中使用到了Consumer

public class PageReadListener implements ReadListener {/*** Single handle the amount of data*/public static int BATCH_COUNT = 100;/*** Temporary storage of data*/private List cachedDataList = ListUtils.newArrayListWithExpectedSize(BATCH_COUNT);/*** consumer*/private final Consumer> consumer;public PageReadListener(Consumer> consumer) {this.consumer = consumer;}@Overridepublic void invoke(T data, AnalysisContext context) {// 每一行数据添加进缓存list中cachedDataList.add(data);if (cachedDataList.size() >= BATCH_COUNT) {// 当超过某个阈值，把它消费掉（此处可存入数据库）consumer.accept(cachedDataList);cachedDataList = ListUtils.newArrayListWithExpectedSize(BATCH_COUNT);}}/*** 确保easyexcel分析完数据被全部消费*/@Overridepublic void doAfterAllAnalysed(AnalysisContext context) {if (CollectionUtils.isNotEmpty(cachedDataList)) {consumer.accept(cachedDataList);}}}

5、接下来调用的是.sheet()方法，我们进入里面看一下

这里我们会传入sheetNo、sheetName参数，调用build()方法创建ExcelReader对象，传入ExcelReaderSheetBuilder构造方法中，最终创建ExcelReaderSheetBuilder对象

6、我们进入build()方法看一下里面到底创建了什么
6.1、生成ExcelReader对象

6.2、初始化ExcelAnalyser

6.3、实例化ExcelAnalyser

7、我们进入choiceExcelExecutor方法看一下，方法通过excel格式，使用不同的执行器
我们看XLSX中，初始化了XlsxReadContext上下文对象，给到analysisContext
又初始化了XlsxSaxAnalyser解析器对象，

	private void choiceExcelExecutor(ReadWorkbook readWorkbook) throws Exception {ExcelTypeEnum excelType = ExcelTypeEnum.valueOf(readWorkbook);switch (excelType) {case XLS:POIFSFileSystem poifsFileSystem;if (readWorkbook.getFile() != null) {poifsFileSystem = new POIFSFileSystem(readWorkbook.getFile());} else {poifsFileSystem = new POIFSFileSystem(readWorkbook.getInputStream());}// So in encrypted excel, it looks like XLS but it's actually XLSXif (poifsFileSystem.getRoot().hasEntry(Decryptor.DEFAULT_POIFS_ENTRY)) {InputStream decryptedStream = null;try {decryptedStream = DocumentFactoryHelper.getDecryptedStream(poifsFileSystem.getRoot().getFileSystem(), readWorkbook.getPassword());XlsxReadContext xlsxReadContext = new DefaultXlsxReadContext(readWorkbook, ExcelTypeEnum.XLSX);analysisContext = xlsxReadContext;excelReadExecutor = new XlsxSaxAnalyser(xlsxReadContext, decryptedStream);return;} finally {IOUtils.closeQuietly(decryptedStream);// as we processed the full stream already, we can close the filesystem here// otherwise file handles are leakedpoifsFileSystem.close();}}if (readWorkbook.getPassword() != null) {Biff8EncryptionKey.setCurrentUserPassword(readWorkbook.getPassword());}XlsReadContext xlsReadContext = new DefaultXlsReadContext(readWorkbook, ExcelTypeEnum.XLS);xlsReadContext.xlsReadWorkbookHolder().setPoifsFileSystem(poifsFileSystem);analysisContext = xlsReadContext;excelReadExecutor = new XlsSaxAnalyser(xlsReadContext);break;case XLSX:XlsxReadContext xlsxReadContext = new DefaultXlsxReadContext(readWorkbook, ExcelTypeEnum.XLSX);analysisContext = xlsxReadContext;excelReadExecutor = new XlsxSaxAnalyser(xlsxReadContext, null);break;case CSV:CsvReadContext csvReadContext = new DefaultCsvReadContext(readWorkbook, ExcelTypeEnum.CSV);analysisContext = csvReadContext;excelReadExecutor = new CsvExcelReadExecutor(csvReadContext);break;default:break;}}

7.1、我们进入new XlsxSaxAnalyser(xlsxReadContext, null)方法看一下,这里使用到SAX模式模式解析excel

public XlsxSaxAnalyser(XlsxReadContext xlsxReadContext, InputStream decryptedStream) throws Exception {this.xlsxReadContext = xlsxReadContext;// 初始化缓存XlsxReadWorkbookHolder xlsxReadWorkbookHolder = xlsxReadContext.xlsxReadWorkbookHolder();OPCPackage pkg = readOpcPackage(xlsxReadWorkbookHolder, decryptedStream);xlsxReadWorkbookHolder.setOpcPackage(pkg);// Read the Shared information StringsPackagePart sharedStringsTablePackagePart = pkg.getPart(SHARED_STRINGS_PART_NAME);if (sharedStringsTablePackagePart != null) {// 指定默认缓存defaultReadCache(xlsxReadWorkbookHolder, sharedStringsTablePackagePart);// 分析sharedStringsTable.xml，解析excel所有数据到readCacheanalysisSharedStringsTable(sharedStringsTablePackagePart.getInputStream(), xlsxReadWorkbookHolder);}XSSFReader xssfReader = new XSSFReader(pkg);analysisUse1904WindowDate(xssfReader, xlsxReadWorkbookHolder);// 设置样式setStylesTable(xlsxReadWorkbookHolder, xssfReader);sheetList = new ArrayList<>();sheetMap = new HashMap<>();commentsTableMap = new HashMap<>();Map packageRelationshipCollectionMap = MapUtils.newHashMap();xlsxReadWorkbookHolder.setPackageRelationshipCollectionMap(packageRelationshipCollectionMap);// 获取所有sheet页XSSFReader.SheetIterator ite = (XSSFReader.SheetIterator)xssfReader.getSheetsData();int index = 0;if (!ite.hasNext()) {throw new ExcelAnalysisException("Can not find any sheet!");}// 遍历所有sheet页while (ite.hasNext()) {InputStream inputStream = ite.next();// 保存所有sheet页sheetList.add(new ReadSheet(index, ite.getSheetName()));// 保存每个sheet页的输入流sheetMap.put(index, inputStream);if (xlsxReadContext.readWorkbookHolder().getExtraReadSet().contains(CellExtraTypeEnum.COMMENT)) {CommentsTable commentsTable = ite.getSheetComments();if (null != commentsTable) {commentsTableMap.put(index, commentsTable);}}if (xlsxReadContext.readWorkbookHolder().getExtraReadSet().contains(CellExtraTypeEnum.HYPERLINK)) {PackageRelationshipCollection packageRelationshipCollection = Optional.ofNullable(ite.getSheetPart()).map(packagePart -> {try {return packagePart.getRelationships();} catch (InvalidFormatException e) {log.warn("Reading the Relationship failed", e);return null;}}).orElse(null);if (packageRelationshipCollection != null) {packageRelationshipCollectionMap.put(index, packageRelationshipCollection);}}index++;}}

7.2、我们进入analysisSharedStringsTable方法，可以看到创建了一个SharedStringsTableHandler处理器

private void analysisSharedStringsTable(InputStream sharedStringsTableInputStream,XlsxReadWorkbookHolder xlsxReadWorkbookHolder) throws Exception {ContentHandler handler = new SharedStringsTableHandler(xlsxReadWorkbookHolder.getReadCache());parseXmlSource(sharedStringsTableInputStream, handler);xlsxReadWorkbookHolder.getReadCache().putFinished();}

7.3、再进入parseXmlSource看到xmlReader.setContentHandler(handler)这一行代码，设置了SharedStringsTableHandler处理器

private void parseXmlSource(InputStream inputStream, ContentHandler handler) {InputSource inputSource = new InputSource(inputStream);try {SAXParserFactory saxFactory;String xlsxSAXParserFactoryName = xlsxReadContext.xlsxReadWorkbookHolder().getSaxParserFactoryName();if (StringUtils.isEmpty(xlsxSAXParserFactoryName)) {saxFactory = SAXParserFactory.newInstance();} else {saxFactory = SAXParserFactory.newInstance(xlsxSAXParserFactoryName, null);}try {saxFactory.setFeature("http://apache.org/xml/features/disallow-doctype-decl", true);} catch (Throwable ignore) {}try {saxFactory.setFeature("http://xml.org/sax/features/external-general-entities", false);} catch (Throwable ignore) {}try {saxFactory.setFeature("http://xml.org/sax/features/external-parameter-entities", false);} catch (Throwable ignore) {}SAXParser saxParser = saxFactory.newSAXParser();XMLReader xmlReader = saxParser.getXMLReader();xmlReader.setContentHandler(handler);xmlReader.parse(inputSource);inputStream.close();} catch (IOException | ParserConfigurationException | SAXException e) {throw new ExcelAnalysisException(e);} finally {if (inputStream != null) {try {inputStream.close();} catch (IOException e) {throw new ExcelAnalysisException("Can not close 'inputStream'!");}}}}

7.4、我们将端点打在，发现下一步进入到这里面了


7.5、excel所有数据读取到readcache中


8、调用.doRead()方法，开始SAX解析

8.1、build()方法

8.2、进入read()方法

8.3、继续进入

9、设置sheetList，并调用执行器开始执行解析

@Overridepublic void analysis(List readSheetList, Boolean readAll) {try {if (!readAll && CollectionUtils.isEmpty(readSheetList)) {throw new IllegalArgumentException("Specify at least one read sheet.");}analysisContext.readWorkbookHolder().setParameterSheetDataList(readSheetList);analysisContext.readWorkbookHolder().setReadAll(readAll);try {excelReadExecutor.execute();} catch (ExcelAnalysisStopException e) {if (LOGGER.isDebugEnabled()) {LOGGER.debug("Custom stop!");}}} catch (RuntimeException e) {finish();throw e;} catch (Throwable e) {finish();throw new ExcelAnalysisException(e);}}

9.1、我们调用的XlsxSaxAnalyser解析器

@Overridepublic void execute() {for (ReadSheet readSheet : sheetList) {readSheet = SheetUtils.match(readSheet, xlsxReadContext);if (readSheet != null) {xlsxReadContext.currentSheet(readSheet);// 解析输入流parseXmlSource(sheetMap.get(readSheet.getSheetNo()), new XlsxRowHandler(xlsxReadContext));// 读取commentreadComments(readSheet);// 读取最后一个sheetxlsxReadContext.analysisEventProcessor().endSheet(xlsxReadContext);}}}

10、进入parseXmlSource()方法，发现和之前的sax差不多，还是看一下传入的ContentHandler参数具体实现,进入XlsxRowHandler 内部

public class XlsxRowHandler extends DefaultHandler {private final XlsxReadContext xlsxReadContext;private static final Map XLSX_CELL_HANDLER_MAP = new HashMap(32);static {CellFormulaTagHandler cellFormulaTagHandler = new CellFormulaTagHandler();XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.CELL_FORMULA_TAG, cellFormulaTagHandler);XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.X_CELL_FORMULA_TAG, cellFormulaTagHandler);CellInlineStringValueTagHandler cellInlineStringValueTagHandler = new CellInlineStringValueTagHandler();XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.CELL_INLINE_STRING_VALUE_TAG, cellInlineStringValueTagHandler);XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.X_CELL_INLINE_STRING_VALUE_TAG, cellInlineStringValueTagHandler);CellTagHandler cellTagHandler = new CellTagHandler();XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.CELL_TAG, cellTagHandler);XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.X_CELL_TAG, cellTagHandler);CellValueTagHandler cellValueTagHandler = new CellValueTagHandler();XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.CELL_VALUE_TAG, cellValueTagHandler);XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.X_CELL_VALUE_TAG, cellValueTagHandler);CountTagHandler countTagHandler = new CountTagHandler();XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.DIMENSION_TAG, countTagHandler);XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.X_DIMENSION_TAG, countTagHandler);HyperlinkTagHandler hyperlinkTagHandler = new HyperlinkTagHandler();XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.HYPERLINK_TAG, hyperlinkTagHandler);XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.X_HYPERLINK_TAG, hyperlinkTagHandler);MergeCellTagHandler mergeCellTagHandler = new MergeCellTagHandler();XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.MERGE_CELL_TAG, mergeCellTagHandler);XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.X_MERGE_CELL_TAG, mergeCellTagHandler);RowTagHandler rowTagHandler = new RowTagHandler();XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.ROW_TAG, rowTagHandler);XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.X_ROW_TAG, rowTagHandler);}public XlsxRowHandler(XlsxReadContext xlsxReadContext) {this.xlsxReadContext = xlsxReadContext;}@Overridepublic void startElement(String uri, String localName, String name, Attributes attributes) throws SAXException {XlsxTagHandler handler = XLSX_CELL_HANDLER_MAP.get(name);if (handler == null || !handler.support(xlsxReadContext)) {return;}// 队列保存当前tagxlsxReadContext.xlsxReadSheetHolder().getTagDeque().push(name);// 调用具体的startElement实现方法handler.startElement(xlsxReadContext, name, attributes);}@Overridepublic void characters(char[] ch, int start, int length) throws SAXException {String currentTag = xlsxReadContext.xlsxReadSheetHolder().getTagDeque().peek();if (currentTag == null) {return;}XlsxTagHandler handler = XLSX_CELL_HANDLER_MAP.get(currentTag);if (handler == null || !handler.support(xlsxReadContext)) {return;}handler.characters(xlsxReadContext, ch, start, length);}@Overridepublic void endElement(String uri, String localName, String name) throws SAXException {XlsxTagHandler handler = XLSX_CELL_HANDLER_MAP.get(name);if (handler == null || !handler.support(xlsxReadContext)) {return;}// 调用具体的endElement实现方法handler.endElement(xlsxReadContext, name);// 出队xlsxReadContext.xlsxReadSheetHolder().getTagDeque().pop();}}

10.1、多种startElement实现

10.2、多种endElement实现

11、进入用到的重要的几个类CellTagHandler、RowTagHandler
CellTagHandler
读取cell的值，并放入tempCellData

public class CellTagHandler extends AbstractXlsxTagHandler {private static final int DEFAULT_FORMAT_INDEX = 0;@Overridepublic void startElement(XlsxReadContext xlsxReadContext, String name, Attributes attributes) {XlsxReadSheetHolder xlsxReadSheetHolder = xlsxReadContext.xlsxReadSheetHolder();xlsxReadSheetHolder.setColumnIndex(PositionUtils.getCol(attributes.getValue(ExcelXmlConstants.ATTRIBUTE_R),xlsxReadSheetHolder.getColumnIndex()));// t="s" ,it means String// t="str" ,it means String,but does not need to be read in the 'sharedStrings.xml'// t="inlineStr" ,it means String,but does not need to be read in the 'sharedStrings.xml'// t="b" ,it means Boolean// t="e" ,it means Error// t="n" ,it means Number// t is null ,it means Empty or NumberCellDataTypeEnum type = CellDataTypeEnum.buildFromCellType(attributes.getValue(ExcelXmlConstants.ATTRIBUTE_T));xlsxReadSheetHolder.setTempCellData(new ReadCellData<>(type));xlsxReadSheetHolder.setTempData(new StringBuilder());// Put in data transformation informationString dateFormatIndex = attributes.getValue(ExcelXmlConstants.ATTRIBUTE_S);int dateFormatIndexInteger;if (StringUtils.isEmpty(dateFormatIndex)) {dateFormatIndexInteger = DEFAULT_FORMAT_INDEX;} else {dateFormatIndexInteger = Integer.parseInt(dateFormatIndex);}xlsxReadSheetHolder.getTempCellData().setDataFormatData(xlsxReadContext.xlsxReadWorkbookHolder().dataFormatData(dateFormatIndexInteger));}@Overridepublic void endElement(XlsxReadContext xlsxReadContext, String name) {XlsxReadSheetHolder xlsxReadSheetHolder = xlsxReadContext.xlsxReadSheetHolder();ReadCellData tempCellData = xlsxReadSheetHolder.getTempCellData();StringBuilder tempData = xlsxReadSheetHolder.getTempData();String tempDataString = tempData.toString();CellDataTypeEnum oldType = tempCellData.getType();switch (oldType) {case STRING:// In some cases, although cell type is a string, it may be an empty tagif (StringUtils.isEmpty(tempDataString)) {break;}String stringValue = xlsxReadContext.readWorkbookHolder().getReadCache().get(Integer.valueOf(tempDataString));tempCellData.setStringValue(stringValue);break;case DIRECT_STRING:case ERROR:tempCellData.setStringValue(tempDataString);tempCellData.setType(CellDataTypeEnum.STRING);break;case BOOLEAN:if (StringUtils.isEmpty(tempDataString)) {tempCellData.setType(CellDataTypeEnum.EMPTY);break;}tempCellData.setBooleanValue(BooleanUtils.valueOf(tempData.toString()));break;case NUMBER:case EMPTY:if (StringUtils.isEmpty(tempDataString)) {tempCellData.setType(CellDataTypeEnum.EMPTY);break;}tempCellData.setType(CellDataTypeEnum.NUMBER);tempCellData.setNumberValue(BigDecimal.valueOf(Double.parseDouble(tempDataString)));break;default:throw new IllegalStateException("Cannot set values now");}if (tempCellData.getStringValue() != null&& xlsxReadContext.currentReadHolder().globalConfiguration().getAutoTrim()) {tempCellData.setStringValue(tempCellData.getStringValue().trim());}tempCellData.checkEmpty();tempCellData.setRowIndex(xlsxReadSheetHolder.getRowIndex());tempCellData.setColumnIndex(xlsxReadSheetHolder.getColumnIndex());xlsxReadSheetHolder.getCellMap().put(xlsxReadSheetHolder.getColumnIndex(), tempCellData);}
}

RowTagHandler
当一行读取完毕后，调用分析事件处理器，处理一行数据
xlsxReadContext.analysisEventProcessor().endRow(xlsxReadContext);

public class RowTagHandler extends AbstractXlsxTagHandler {@Overridepublic void startElement(XlsxReadContext xlsxReadContext, String name, Attributes attributes) {XlsxReadSheetHolder xlsxReadSheetHolder = xlsxReadContext.xlsxReadSheetHolder();int rowIndex = PositionUtils.getRowByRowTagt(attributes.getValue(ExcelXmlConstants.ATTRIBUTE_R),xlsxReadSheetHolder.getRowIndex());Integer lastRowIndex = xlsxReadContext.readSheetHolder().getRowIndex();while (lastRowIndex + 1 < rowIndex) {xlsxReadContext.readRowHolder(new ReadRowHolder(lastRowIndex + 1, RowTypeEnum.EMPTY,xlsxReadSheetHolder.getGlobalConfiguration(), new LinkedHashMap()));xlsxReadContext.analysisEventProcessor().endRow(xlsxReadContext);xlsxReadSheetHolder.setColumnIndex(null);xlsxReadSheetHolder.setCellMap(new LinkedHashMap());lastRowIndex++;}xlsxReadSheetHolder.setRowIndex(rowIndex);}@Overridepublic void endElement(XlsxReadContext xlsxReadContext, String name) {XlsxReadSheetHolder xlsxReadSheetHolder = xlsxReadContext.xlsxReadSheetHolder();RowTypeEnum rowType = MapUtils.isEmpty(xlsxReadSheetHolder.getCellMap()) ? RowTypeEnum.EMPTY : RowTypeEnum.DATA;// It's possible that all of the cells in the row are emptyif (rowType == RowTypeEnum.DATA) {boolean hasData = false;for (Cell cell : xlsxReadSheetHolder.getCellMap().values()) {if (!(cell instanceof ReadCellData)) {hasData = true;break;}ReadCellData readCellData = (ReadCellData)cell;if (readCellData.getType() != CellDataTypeEnum.EMPTY) {hasData = true;break;}}if (!hasData) {rowType = RowTypeEnum.EMPTY;}}xlsxReadContext.readRowHolder(new ReadRowHolder(xlsxReadSheetHolder.getRowIndex(), rowType,xlsxReadSheetHolder.getGlobalConfiguration(), xlsxReadSheetHolder.getCellMap()));xlsxReadContext.analysisEventProcessor().endRow(xlsxReadContext);xlsxReadSheetHolder.setColumnIndex(null);xlsxReadSheetHolder.setCellMap(new LinkedHashMap<>());}}

12、进入xlsxReadContext.analysisEventProcessor().endRow(xlsxReadContext)/endRow()方法

public void endRow(AnalysisContext analysisContext) {if (RowTypeEnum.EMPTY.equals(analysisContext.readRowHolder().getRowType())) {if (LOGGER.isDebugEnabled()) {LOGGER.debug("Empty row!");}if (analysisContext.readWorkbookHolder().getIgnoreEmptyRow()) {return;}}dealData(analysisContext);}

13、继续进入dealData方法

private void dealData(AnalysisContext analysisContext) {ReadRowHolder readRowHolder = analysisContext.readRowHolder();Map> cellDataMap = (Map)readRowHolder.getCellMap();readRowHolder.setCurrentRowAnalysisResult(cellDataMap);int rowIndex = readRowHolder.getRowIndex();int currentHeadRowNumber = analysisContext.readSheetHolder().getHeadRowNumber();boolean isData = rowIndex >= currentHeadRowNumber;// Last head column 保存表头数据if (!isData && currentHeadRowNumber == rowIndex + 1) {buildHead(analysisContext, cellDataMap);}// Now is data	调用一开传入的监听器，处理一行数据for (ReadListener readListener : analysisContext.currentReadHolder().readListenerList()) {try {if (isData) {// 处理数据readListener.invoke(readRowHolder.getCurrentRowAnalysisResult(), analysisContext);} else {// 处理表头readListener.invokeHead(cellDataMap, analysisContext);}} catch (Exception e) {onException(analysisContext, e);break;}if (!readListener.hasNext(analysisContext)) {throw new ExcelAnalysisStopException();}}}

14、进入readComments()方法,读取额外信息（批注、超链接、合并单元格信息读取）

	private void readComments(ReadSheet readSheet) {if (!xlsxReadContext.readWorkbookHolder().getExtraReadSet().contains(CellExtraTypeEnum.COMMENT)) {return;}CommentsTable commentsTable = commentsTableMap.get(readSheet.getSheetNo());if (commentsTable == null) {return;}Iterator cellAddresses = commentsTable.getCellAddresses();while (cellAddresses.hasNext()) {CellAddress cellAddress = cellAddresses.next();XSSFComment cellComment = commentsTable.findCellComment(cellAddress);CellExtra cellExtra = new CellExtra(CellExtraTypeEnum.COMMENT, cellComment.getString().toString(),cellAddress.getRow(), cellAddress.getColumn());xlsxReadContext.readSheetHolder().setCellExtra(cellExtra);xlsxReadContext.analysisEventProcessor().extra(xlsxReadContext);}}

15、最后进入.endSheet(xlsxReadContext)方法

@Overridepublic void endSheet(AnalysisContext analysisContext) {// 这里会调用所有监听器中的doAfterAllAnalysed方法，执行最后的操作for (ReadListener readListener : analysisContext.currentReadHolder().readListenerList()) {readListener.doAfterAllAnalysed(analysisContext);}}

16、在读取完毕之后，执行finish()方法，关闭所有流

5、总结

从上面使用和源码可以看得出阿里，poi能做的easyExcel也能做，而且做的更加优秀（防止内存溢出、性能），更加的方便（使用），所以阿里的EasyExcel做的那么优秀，还是有很多地方值得我们学习的，并且是开源的就非常棒！