这块内容有点多，单独拉出来，要不看着太乱。

导入(读取)(read)-示例及核心部件

代码：

java">EasyExcel.read(file.getInputStream(), UserExcelVo.class, userListener).extraRead(CellExtraTypeEnum.MERGE).sheet(0) // 指定读取哪个sheet.headRowNumber(1) // 指定标题行.doRead(); // 执行读取

导入(读取)(read)-核心部件

以上面代码为例。

EasyExcel(EasyExcelFactory) # 入口

read() # read()方法用于构建workbook(工作簿)对象，new ExcelReaderBuilder()

java">public class EasyExcelFactory {public static ExcelReaderBuilder read() {return new ExcelReaderBuilder();}
}

java">public class ExcelReaderBuilder extends AbstractExcelReaderParameterBuilder<ExcelReaderBuilder, ReadWorkbook> {/*** Workbook*/private final ReadWorkbook readWorkbook;public ExcelReaderBuilder() {this.readWorkbook = new ReadWorkbook();}
}

doReadAll()

java">public class ExcelReaderBuilder extends AbstractExcelReaderParameterBuilder<ExcelReaderBuilder, ReadWorkbook> {public void doReadAll() {try (ExcelReader excelReader = build()) {excelReader.readAll();}}
}

java">public class ExcelReader implements Closeable {public void readAll() {excelAnalyser.analysis(null, Boolean.TRUE);}
}

java">public class ExcelAnalyserImpl implements ExcelAnalyser {
@Overridepublic void analysis(List<ReadSheet> 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);}}
}

这里选XlsxSaxAnalyser这个实现类吧

java">public class XlsxSaxAnalyser implements ExcelReadExecutor {
@Overridepublic void execute() {for (ReadSheet readSheet : sheetList) {readSheet = SheetUtils.match(readSheet, xlsxReadContext);if (readSheet != null) {xlsxReadContext.currentSheet(readSheet);parseXmlSource(sheetMap.get(readSheet.getSheetNo()), new XlsxRowHandler(xlsxReadContext));// Read commentsreadComments(readSheet);// The last sheet is readxlsxReadContext.analysisEventProcessor().endSheet(xlsxReadContext);}}}
}

然后到这个类XlsxRowHandler，这里使用了策略模式，会根据xml不同的标签拿到对应的处理类来进行处理。

java">public class XlsxRowHandler extends DefaultHandler {
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);XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.NS2_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);XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.NS2_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);XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.NS2_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);XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.NS2_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);XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.NS2_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);XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.NS2_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);XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.NS2_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);XLSX_CELL_HANDLER_MAP.put(ExcelXmlConstants.NS2_ROW_TAG, rowTagHandler);}
}

从上面代码找到RowTagHandler这个类，每解析了一行数据后都会进行处理

java">public class RowTagHandler extends AbstractXlsxTagHandler {
@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<>());}
}

然后看endRow()方法

java">public class DefaultAnalysisEventProcessor implements AnalysisEventProcessor {@Overridepublic 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);}
}

进入到dealData方法中

java">private void dealData(AnalysisContext analysisContext) {ReadRowHolder readRowHolder = analysisContext.readRowHolder();Map<Integer, ReadCellData<?>> cellDataMap = (Map)readRowHolder.getCellMap();readRowHolder.setCurrentRowAnalysisResult(cellDataMap);int rowIndex = readRowHolder.getRowIndex();int currentHeadRowNumber = analysisContext.readSheetHolder().getHeadRowNumber();boolean isData = rowIndex >= currentHeadRowNumber;// Last head columnif (!isData && currentHeadRowNumber == rowIndex + 1) {buildHead(analysisContext, cellDataMap);}// Now is datafor (ReadListener readListener : analysisContext.currentReadHolder().readListenerList()) {try {if (isData) {readListener.invoke(readRowHolder.getCurrentRowAnalysisResult(), analysisContext);} else {readListener.invokeHead(cellDataMap, analysisContext);}} catch (Exception e) {onException(analysisContext, e);break;}if (!readListener.hasNext(analysisContext)) {throw new ExcelAnalysisStopException();}}}

这里可以看到，每解析了一行数据后都会逐个调用监听器的invoke方法（包括easyexcel默认的监听器和我们自定义的监听器）

跟踪invoke()方法，选用ModelBuildEventListener这个实现类吧

进入到ModelBuildEventListener实现类，这个实现类是easyexcel自带的默认的监听器，这个监听器的主要作用是将excel的每行数据封装

java">public class ModelBuildEventListener implements IgnoreExceptionReadListener<Map<Integer, ReadCellData<?>>> {@Overridepublic void invoke(Map<Integer, ReadCellData<?>> cellDataMap, AnalysisContext context) {ReadSheetHolder readSheetHolder = context.readSheetHolder();if (HeadKindEnum.CLASS.equals(readSheetHolder.excelReadHeadProperty().getHeadKind())) {context.readRowHolder().setCurrentRowAnalysisResult(buildUserModel(cellDataMap, readSheetHolder, context));return;}context.readRowHolder().setCurrentRowAnalysisResult(buildNoModel(cellDataMap, readSheetHolder, context));}
}

进入到buildUserModel方法中

java">private Object buildUserModel(Map<Integer, ReadCellData<?>> cellDataMap, ReadSheetHolder readSheetHolder,AnalysisContext context) {ExcelReadHeadProperty excelReadHeadProperty = readSheetHolder.excelReadHeadProperty();Object resultModel;try {resultModel = excelReadHeadProperty.getHeadClazz().newInstance();} catch (Exception e) {throw new ExcelDataConvertException(context.readRowHolder().getRowIndex(), 0,new ReadCellData<>(CellDataTypeEnum.EMPTY), null,"Can not instance class: " + excelReadHeadProperty.getHeadClazz().getName(), e);}Map<Integer, Head> headMap = excelReadHeadProperty.getHeadMap();BeanMap dataMap = BeanMapUtils.create(resultModel);for (Map.Entry<Integer, Head> entry : headMap.entrySet()) {Integer index = entry.getKey();Head head = entry.getValue();String fieldName = head.getFieldName();if (!cellDataMap.containsKey(index)) {continue;}ReadCellData<?> cellData = cellDataMap.get(index);Object value = ConverterUtils.convertToJavaObject(cellData, head.getField(),ClassUtils.declaredExcelContentProperty(dataMap, readSheetHolder.excelReadHeadProperty().getHeadClazz(),fieldName, readSheetHolder), readSheetHolder.converterMap(), context,context.readRowHolder().getRowIndex(), index);if (value != null) {dataMap.put(fieldName, value);}}return resultModel;}

可以看到，先是通过反射创建对象，然后根据反射对各个对象赋值。

至此，excel的一行数据就被easyexcel默认的监听器解析成了对应的java对象，然后我们在自定义的监听器中就能拿到这个对象并进行处理了。