java根据动态头导出excel文件

一、需求背景

用户可选择列表中列展示，当选择好之后点击导出，excel中只导出用户选择列的数据

1、调用接口将表头传给给后端

2、请求结果展示

3、核心代码

pom包

1、工具类，注意异常抛出类如报错，需自定义异常类

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.reflect.Field;
import java.net.URLEncoder;
import java.nio.charset.StandardCharsets;
import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;import cn.hutool.core.util.ReflectUtil;
import com.alibaba.excel.EasyExcel;
import com.alibaba.excel.EasyExcelFactory;
import com.alibaba.excel.ExcelWriter;
import com.alibaba.excel.write.metadata.WriteSheet;
import com.alibaba.excel.write.metadata.fill.FillConfig;
import com.mbcloud.cloud.commons.exception.ApiException;
import lombok.SneakyThrows;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.StringUtils;import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.springframework.stereotype.Component;
import org.springframework.web.multipart.MultipartFile;import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;@Component
@Slf4j
public class ExcelUtil {/*** 从 sheet 中获取指定行列的单元格值** @param sheet        表单* @param rowNumber    行号* @param columnNumber 列号* @return 统一返回字符串类型，null 表示找不到*/public static String getCellValue(Sheet sheet, int rowNumber, int columnNumber) {Row row = sheet.getRow(rowNumber);if (null == row) {return null;}Cell cell = row.getCell(columnNumber);if (null == cell) {return null;}// 只处理数字、文本、公式结果为数字、文本的，其余认为错误switch (cell.getCellTypeEnum()) {case NUMERIC:// 保留两位小数，并处理科学计数法DecimalFormat df = new DecimalFormat("0.00");return df.format(cell.getNumericCellValue());case STRING:return cell.getStringCellValue();case FORMULA:switch (cell.getCachedFormulaResultTypeEnum()) {case STRING:return cell.getStringCellValue();case NUMERIC:NumberFormat nf = NumberFormat.getInstance();nf.setGroupingUsed(false);return String.valueOf(nf.format(cell.getNumericCellValue()));default:return null;}default:return null;}}/*** 根据模板导出数据 单个sheet** @param response     返回对象* @param dataList     导出的数据集合* @param object       填充对象* @param fileName     文件名称* @param templateName 模板名称* @throws Exception*/public void exportTemplateExcel(HttpServletResponse response, List<?> dataList, Object object,String fileName, String templateName) throws Exception {InputStream inputStream = this.getClass().getResourceAsStream(templateName);FillConfig fillConfig = FillConfig.builder().forceNewRow(Boolean.TRUE).build();ExcelWriter excelWriter = EasyExcelFactory.write(getOutputStream(fileName, response)).withTemplate(inputStream).build();WriteSheet writeSheet0 = EasyExcelFactory.writerSheet(0).build();excelWriter.fill(object, fillConfig, writeSheet0);excelWriter.fill(dataList, fillConfig, writeSheet0);excelWriter.finish();}/*** 构建输出流** @param fileName 文件名称* @param response 输出流* @return* @throws Exception*/private OutputStream getOutputStream(String fileName, HttpServletResponse response) throws Exception {URLEncoder.encode(fileName, StandardCharsets.UTF_8.name());response.setContentType("application/vnd.ms-excel");response.setCharacterEncoding(StandardCharsets.UTF_8.name());response.setHeader("Content-Disposition", "attachment;filename=" + fileName + ".xlsx");return response.getOutputStream();}/*** 文件格式校验** @param file 文件*/public  void checkFile(MultipartFile file) throws ApiException{if (file == null) {throw new ApiException("500", "文件不能为空");}String filename = file.getOriginalFilename();if (StringUtils.isEmpty(filename)) {throw new ApiException("500", "文件不能为空");}if (!filename.endsWith(".xls") && !filename.endsWith(".xlsx")) {throw new ApiException("500", "请上传.xls文件或者.xlsx文件");}}/*** 动态表头生成excel* @param headers 要生成的表头* @param dataList 数据* @param response* @param fileName 文件名称* @param titleName title名称* @param <T>*/public static <T> void dynamicExportExcel(List<ExcelHeader> headers, List<T> dataList, HttpServletResponse response, String fileName, String titleName) {long startTime = System.currentTimeMillis();List<List<T>> allList = new ArrayList<>();for (T detail : dataList) {allList.addAll(dataList(headers, detail));}try (ServletOutputStream outputStream = response.getOutputStream()) {String name = com.sun.deploy.net.URLEncoder.encode(fileName, "UTF-8").replaceAll("\\+", "%20");response.setContentType("application/vnd.ms-excel");response.setCharacterEncoding("utf-8");response.setHeader("Content-disposition", "attachment;filename*=utf-8''" + name + ".xlsx");//设置响应头response.setHeader("mime","application/vnd.ms-excel");EasyExcel.write(outputStream).head(headers(headers))//表格标题占位.relativeHeadRowIndex(1)//文件样式.registerWriteHandler(new CustomTitleWriteHandler(headers.size(),titleName)).registerWriteHandler(new CellStyle()).sheet(fileName).doWrite(allList);} catch (IOException e) {log.error("生成动态EXL失败，字段", e);}long endTime = System.currentTimeMillis();log.info("动态导出耗时:{}", endTime - startTime);}//excel表头public static List<List<String>> headers(List<ExcelHeader> excelHeaders) {List<List<String>> headers = new ArrayList<>();for (ExcelHeader header : excelHeaders) {List<String> head = new ArrayList<>();head.add(header.getHeadName());headers.add(head);}return headers;}/*** 要导出的字段** @param exportFields 表头集合* @param obj          数据对象* @return 集合*/@SneakyThrowspublic static <T> List<List<T>> dataList(List<ExcelHeader> exportFields, T obj) {List<List<T>> list = new ArrayList<>();List<T> data = new ArrayList<>();List<String> propList = exportFields.stream().map(ExcelHeader::getFieldName).collect(Collectors.toList());//先根据反射获取实体类的class对象Class<?> objClass = obj.getClass();//设置实体类属性的集合Field[] fields = ReflectUtil.getFields(objClass);for (String prop : propList) {//循环实体类对象集合for (Field field : fields) {field.setAccessible(true);//判断实体类属性跟特定字段集合名是否一样if (field.getName().equals(prop)) {T object = (T) field.get(obj);//获取属性对应的值if(null == object){object = (T) "--";}else{if(object instanceof LocalDate){object = (T) DateUtil.localDateToString((LocalDate)object);}if(object instanceof LocalDateTime){object = (T) DateUtil.localDateTimeToString((LocalDateTime)object);}}data.add(object);}}}list.add(data);return list;}}

2、标题设置类

import com.alibaba.excel.write.handler.SheetWriteHandler;
import com.alibaba.excel.write.metadata.holder.WriteSheetHolder;
import com.alibaba.excel.write.metadata.holder.WriteWorkbookHolder;
import org.apache.poi.ss.usermodel.CellStyle;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.ss.util.CellRangeAddress;public class CustomTitleWriteHandler implements SheetWriteHandler {/*** 标题*/private final String fileName;/*** 字段个数*/private final Integer count;public CustomTitleWriteHandler(Integer count,String fileName) {this.fileName = fileName;this.count = count;}@Overridepublic void beforeSheetCreate(WriteWorkbookHolder writeWorkbookHolder, WriteSheetHolder writeSheetHolder) {}@Overridepublic void afterSheetCreate(WriteWorkbookHolder writeWorkbookHolder, WriteSheetHolder writeSheetHolder) {// 获取clazz所有的属性Workbook workbook = writeWorkbookHolder.getWorkbook();Sheet sheet = workbook.getSheetAt(0);Row row1 = sheet.createRow(0);row1.setHeight((short) 800);Cell cell = row1.createCell(0);//设置标题cell.setCellValue(fileName);CellStyle cellStyle = workbook.createCellStyle();cellStyle.setVerticalAlignment(VerticalAlignment.CENTER);cellStyle.setAlignment(HorizontalAlignment.CENTER);Font font = workbook.createFont();font.setBold(true);font.setFontHeight((short) 400);font.setFontName("宋体");cellStyle.setFont(font);cell.setCellStyle(cellStyle);sheet.addMergedRegionUnsafe(new CellRangeAddress(0, 0, 0, count-1));}
}

3、单元各简单设置类

import com.alibaba.excel.metadata.CellData;
import com.alibaba.excel.metadata.Head;
import com.alibaba.excel.write.metadata.holder.WriteSheetHolder;
import com.alibaba.excel.write.style.column.AbstractColumnWidthStyleStrategy;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Sheet;import java.util.List;public class CellStyle extends AbstractColumnWidthStyleStrategy {@Overrideprotected void setColumnWidth(WriteSheetHolder writeSheetHolder, List<CellData> cellDataList, Cell cell, Head head,Integer relativeRowIndex, Boolean isHead) {// 简单设置Sheet sheet = writeSheetHolder.getSheet();sheet.setColumnWidth(cell.getColumnIndex(), 5000);}}

4、controller接收参数

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public class ExcelHeader {/*** 要导出的字段名称英文*/private String fieldName;/*** 要导出的表头名称中文*/private String headName;/*** 排序*/private Integer order;/*** 是否展示*/private Boolean display;}