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0 EasyExcel简介

在数据处理和报表生成的过程中，Excel是一个非常常用的工具。特别是在Java开发中，EasyExcel库因其简单高效而备受欢迎。

EasyExcel是阿里巴巴开源的一个Excel处理库，特别适用于大数据量的Excel文件的读写。它的优点在于使用简单、性能高效，特别适合在Java项目中处理Excel文件。

1 Excel导出工具类

Excel导出工具类ExcelUtil类代码如下：

import com.alibaba.excel.EasyExcel;
import com.alibaba.excel.ExcelWriter;
import com.alibaba.excel.support.ExcelTypeEnum;
import com.alibaba.excel.write.builder.ExcelWriterBuilder;
import com.alibaba.excel.write.metadata.WriteSheet;
import com.alibaba.excel.write.metadata.style.WriteCellStyle;
import com.alibaba.excel.write.metadata.style.WriteFont;
import com.alibaba.excel.write.style.HorizontalCellStyleStrategy;
import com.alibaba.excel.write.style.column.LongestMatchColumnWidthStyleStrategy;
import lombok.Data;
import org.apache.poi.ss.usermodel.*;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.net.URLEncoder;
import java.util.List;@Data
public class ExcelUtil{public static void downloadExcelWithHead(HttpServletResponse response, List<?> list, String sheetName, List<List<String>> rowHead) throws IOException {if (list.isEmpty()) {throw new IllegalArgumentException("列表不能为空！");}Class<?> clazz = list.get(0).getClass();response.setContentType("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");response.setCharacterEncoding("utf-8");String fileName = URLEncoder.encode(sheetName, "UTF-8").replaceAll("\\+", "%20");response.setHeader("Content-disposition", "attachment;filename*=utf-8''" + fileName + ".xlsx");ExcelWriter excelWriter = EasyExcel.write(response.getOutputStream(), clazz).excelType(ExcelTypeEnum.XLSX).build();// 创建 ExcelWriterBuilderExcelWriterBuilder excelWriterBuilder = EasyExcel.write(response.getOutputStream(), clazz).autoCloseStream(true).needHead(true);excelWriterBuilder.registerWriteHandler(new LongestMatchColumnWidthStyleStrategy());excelWriterBuilder.useDefaultStyle(false);// 创建 WriteSheet 并设置动态标题行WriteSheet writeSheet = EasyExcel.writerSheet(sheetName).head(rowHead) // 设置标题行.registerWriteHandler(setCellStyle()) // 设置表头样式.registerWriteHandler(new CustomCellWriteUtil()) // 设置列宽自适应.build();// 写入数据excelWriter.write(list, writeSheet);excelWriter.finish();}}

设置自定义表头样式

其中，downloadExcelWithHead()中调用setCellStyle()方法用于设置表头样式。setCellStyle()方法的代码如下：

    public static HorizontalCellStyleStrategy setCellStyle() {// 表头策略WriteCellStyle headWriteCellStyle = new WriteCellStyle();// 背景设置为白色headWriteCellStyle.setFillForegroundColor(IndexedColors.WHITE.index);headWriteCellStyle.setHorizontalAlignment(HorizontalAlignment.CENTER);headWriteCellStyle.setVerticalAlignment(VerticalAlignment.CENTER);//边框headWriteCellStyle.setBorderBottom(BorderStyle.THIN);headWriteCellStyle.setBorderLeft(BorderStyle.THIN);headWriteCellStyle.setBorderRight(BorderStyle.THIN);headWriteCellStyle.setBorderTop(BorderStyle.THIN);//自动换行headWriteCellStyle.setWrapped(true);WriteFont headWriteFont = new WriteFont();headWriteFont.setBold(true);headWriteFont.setFontName("宋体");headWriteFont.setFontHeightInPoints((short)12);headWriteCellStyle.setWriteFont(headWriteFont);// 内容的策略WriteCellStyle contentWriteCellStyle = new WriteCellStyle();// 这里需要指定 FillPatternType 为FillPatternType.SOLID_FOREGROUND 不然无法显示背景颜色.头默认了 FillPatternType所以可以不指定contentWriteCellStyle.setFillPatternType(FillPatternType.SOLID_FOREGROUND);// 背景白色contentWriteCellStyle.setFillForegroundColor(IndexedColors.WHITE.getIndex());contentWriteCellStyle.setHorizontalAlignment(HorizontalAlignment.CENTER);contentWriteCellStyle.setVerticalAlignment(VerticalAlignment.CENTER);//边框contentWriteCellStyle.setBorderBottom(BorderStyle.THIN);contentWriteCellStyle.setBorderLeft(BorderStyle.THIN);contentWriteCellStyle.setBorderRight(BorderStyle.THIN);contentWriteCellStyle.setBorderTop(BorderStyle.THIN);//自动换行contentWriteCellStyle.setWrapped(true);//文字WriteFont contentWriteFont = new WriteFont();// 字体大小contentWriteFont.setFontHeightInPoints((short)12);contentWriteFont.setFontName("宋体");contentWriteCellStyle.setWriteFont(contentWriteFont);return new HorizontalCellStyleStrategy(headWriteCellStyle, contentWriteCellStyle);}

设置自适应列宽

自适应列宽通过CustomCellWriteUtil类设置，CustomCellWriteUtil类的代码如下：

import com.alibaba.excel.enums.CellDataTypeEnum;
import com.alibaba.excel.metadata.Head;
import com.alibaba.excel.metadata.data.CellData;
import com.alibaba.excel.metadata.data.WriteCellData;
import com.alibaba.excel.write.metadata.holder.WriteSheetHolder;
import com.alibaba.excel.write.style.column.AbstractColumnWidthStyleStrategy;
import org.apache.commons.collections4.CollectionUtils;
import org.apache.poi.ss.usermodel.Cell;import java.util.HashMap;
import java.util.List;
import java.util.Map;/*** excel自适应列宽*/
public class CustomCellWriteUtil extends AbstractColumnWidthStyleStrategy {private static final int MAX_COLUMN_WIDTH = 255;private Map<Integer, Map<Integer, Integer>> CACHE = new HashMap(8);public CustomCellWriteUtil() {}protected void setColumnWidth(WriteSheetHolder writeSheetHolder, List<WriteCellData<?>> cellDataList, Cell cell, Head head, Integer relativeRowIndex, Boolean isHead) {boolean needSetWidth = isHead || !CollectionUtils.isEmpty(cellDataList);if (needSetWidth) {Map<Integer, Integer> maxColumnWidthMap = (Map) CACHE.get(writeSheetHolder.getSheetNo());if (maxColumnWidthMap == null) {maxColumnWidthMap = new HashMap(16);CACHE.put(writeSheetHolder.getSheetNo(), maxColumnWidthMap);}Integer columnWidth = this.dataLength(cellDataList, cell, isHead);if (columnWidth >= 0) {if (columnWidth > 255) {columnWidth = 255;}Integer maxColumnWidth = (Integer) ((Map) maxColumnWidthMap).get(cell.getColumnIndex());if (maxColumnWidth == null || columnWidth > maxColumnWidth) {((Map) maxColumnWidthMap).put(cell.getColumnIndex(), columnWidth);writeSheetHolder.getSheet().setColumnWidth(cell.getColumnIndex(), 7250);}}}}private Integer dataLength(List<WriteCellData<?>> cellDataList, Cell cell, Boolean isHead) {if (isHead) {return cell.getStringCellValue().getBytes().length;} else {CellData cellData = (CellData) cellDataList.get(0);CellDataTypeEnum type = cellData.getType();if (type == null) {return -1;} else {switch (type) {case STRING:return cellData.getStringValue().getBytes().length;case BOOLEAN:return cellData.getBooleanValue().toString().getBytes().length;case NUMBER:return cellData.getNumberValue().toString().getBytes().length;default:return -1;}}}}
}

添加合计行

合计行用于展示数据的总和或其他统计信息。在Controller中调用downloadExcelWithHead()方法导出Excel时，添加合计行和自定义表头形式。

2 调用导出工具类导出Excel表

此处以导出产品明细表为例，新建产品表如下：

entity、mapper、service层省略，在Controller层中添加一个导出产品明细表接口，代码如下：

import com.z.entity.Product;
import com.z.service.ProductService;
import com.z.util.ConvertUtil;
import com.z.util.ExcelUtil;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;@RestController
@RequestMapping("/product")
public class ProductController {@Autowiredprivate ProductService productService;@PostMapping("/export")public void export(HttpServletResponse response) throws IOException {List<Product> dataList = productService.list();if(null == dataList || dataList.isEmpty()){throw new RuntimeException("数据为空，导出失败！");}// 计算合计double totalProductCost = dataList.stream().mapToDouble(data -> data.getProductCost() != null ? data.getProductCost() : 0.0).sum();int totalProductNum = dataList.stream().mapToInt(data -> data.getProductNum() != null ? data.getProductNum() : 0).sum();// 创建合计行Product totalRow = new Product();totalRow.setId("合计");totalRow.setProductCost(totalProductCost);totalRow.setProductNum(totalProductNum);// 添加合计行到列表dataList.add(totalRow);// 创建自定义表头List<List<String>> rowHead = createHead();// 导出 Excel(带标题列，带合计列)ExcelUtil.downloadExcelWithHead(response, dataList, "产品明细表", rowHead);}/*** 设置Excel头* @return*/private List<List<String>> createHead() {List<List<String>> list = new ArrayList<>();// 第一列表头List<String> headRow1 = new ArrayList<>();headRow1.add("产品明细表报表");headRow1.add("test");headRow1.add("产品序号");list.add(headRow1);// 第二列表头List<String> headRow2 = new ArrayList<>();headRow2.add("产品明细表报表");headRow2.add("备注："+"此处可调用方法取值");headRow2.add("产品编号");list.add(headRow2);// 第三列表头List<String> headRow3 = new ArrayList<>();headRow3.add("产品明细表报表");headRow3.add("备注："+"此处可调用方法取值");headRow3.add("产品名称");list.add(headRow3);// 第四列表头List<String> headRow4 = new ArrayList<>();headRow4.add("产品明细表报表");headRow4.add("无");headRow4.add("产品进价");list.add(headRow4);// 第五列表头List<String> headRow5 = new ArrayList<>();headRow5.add("产品明细表报表");headRow5.add("测试");headRow5.add("产品库存");list.add(headRow5);return list;}

其中，在使用createHead()方法设置Excel头时，可以调用service层中的方法，自定义显示特定值。

3 测试结果

最终使用postman调用该导出接口，导出的表格结果如下：