寫在最前面：
　　　　使用的是JAVA POI實現的導出Excel；
　　　　POI 提供了對2003版本的Excel的支持 ---- HSSFWorkbook
　　　　POI 提供了對2007版本以及更高版本的支持 ---- XSSFWorkbook

引入相關依賴：

<dependency><groupId>org.apache.poi</groupId><artifactId>poi-ooxml</artifactId><version>4.1.2</version></dependency> /*** 讀取Excel文件的內容* @param inputStream excel文件，以InputStream的形式傳入* @param sheetName sheet名字* @return 以List返回excel中內容*/public static List<Map<String, String>> readExcel(InputStream inputStream, String sheetName) {//定義工作簿XSSFWorkbook xssfWorkbook = null;try {xssfWorkbook = new XSSFWorkbook(inputStream);} catch (Exception e) {System.out.println("Excel data file cannot be found!");}//定義工作表XSSFSheet xssfSheet;if (sheetName.equals("")) {// 默認取第一個子表xssfSheet = xssfWorkbook.getSheetAt(0);} else {xssfSheet = xssfWorkbook.getSheet(sheetName);}List<Map<String, String>> list = new ArrayList<Map<String, String>>();//定義行//默認第一行為標題行，index = 0XSSFRow titleRow = xssfSheet.getRow(0);//循環取每行的數據for (int rowIndex = 1; rowIndex < xssfSheet.getPhysicalNumberOfRows(); rowIndex++) {XSSFRow xssfRow = xssfSheet.getRow(rowIndex);if (xssfRow == null) {continue;}Map<String, String> map = new LinkedHashMap<String, String>();//循環取每個單元格(cell)的數據for (int cellIndex = 0; cellIndex < xssfRow.getPhysicalNumberOfCells(); cellIndex++) {XSSFCell titleCell = titleRow.getCell(cellIndex);XSSFCell xssfCell = xssfRow.getCell(cellIndex);map.put(getString(titleCell),getString(xssfCell));}list.add(map);}return list;}/*** 把單元格的內容轉為字符串* @param xssfCell 單元格* @return 字符串*/public static String getString(XSSFCell xssfCell) {if (xssfCell == null) {return "";}if (xssfCell.getCellTypeEnum() == CellType.NUMERIC) {return String.valueOf(xssfCell.getNumericCellValue());} else if (xssfCell.getCellTypeEnum() == CellType.BOOLEAN) {return String.valueOf(xssfCell.getBooleanCellValue());} else {return xssfCell.getStringCellValue();}}/*** 把內容寫入Excel* @param list 傳入要寫的內容，此處以一個List內容為例，先把要寫的內容放到一個list中* @param outputStream 把輸出流懟到要寫入的Excel上，準備往里面寫數據*/public static void writeExcel(List<List> list, OutputStream outputStream) {//創建工作簿XSSFWorkbook xssfWorkbook = null;xssfWorkbook = new XSSFWorkbook();//創建工作表XSSFSheet xssfSheet;xssfSheet = xssfWorkbook.createSheet();//創建行XSSFRow xssfRow;//創建列，即單元格CellXSSFCell xssfCell;//把List里面的數據寫到excel中for (int i=0;i<list.size();i++) {//從第一行開始寫入xssfRow = xssfSheet.createRow(i);//創建每個單元格Cell，即列的數據List sub_list =list.get(i);for (int j=0;j<sub_list.size();j++) {xssfCell = xssfRow.createCell(j); //創建單元格xssfCell.setCellValue((String)sub_list.get(j)); //設置單元格內容}}//用輸出流寫到exceltry {xssfWorkbook.write(outputStream);outputStream.flush();outputStream.close();}catch (IOException e) {e.printStackTrace();}}

附：把一個Map中的所有鍵和值分別放到一個list中，再把這兩個list整個放到一個大的list里面，即 [ [key1,key2,key3…] , [value1,value2,value3…] ]

public static List<List> convertMapToList(Map map) {List<List> list = new ArrayList<List>();List<String> key_list = new LinkedList<String>();List<String> value_list = new LinkedList<String>();Set<Entry<String,String>> set = map.entrySet();Iterator<Entry<String,String>> iter1 = set.iterator();while (iter1.hasNext()) {key_list.add(iter1.next().getKey());}list.add(key_list);Collection<String> value = map.values();Iterator<String> iter2 = value.iterator();while (iter2.hasNext()) {value_list.add(iter2.next());}list.add(value_list);return list;}

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導出接口：

package com.wqd.dove.demo.export.controller;import com.wqd.dove.demo.export.mapper.UserMapper; import com.wqd.dove.demo.export.pojo.User; import lombok.RequiredArgsConstructor; import org.apache.poi.xssf.usermodel.XSSFCell; import org.apache.poi.xssf.usermodel.XSSFRow; import org.apache.poi.xssf.usermodel.XSSFSheet; import org.apache.poi.xssf.usermodel.XSSFWorkbook; import org.springframework.web.bind.annotation.GetMapping; 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.io.UnsupportedEncodingException; import java.net.URLEncoder; import java.util.List;/*** @author frank* @description 導出Excel文件控制器* @date 2021/12/18 14:06*/ @RestController @RequiredArgsConstructor @RequestMapping(value = {"/export"}) public class MyExcelExportController {private final UserMapper userMapper;@GetMapping(value = "/excel")public void exportExcel(HttpServletResponse response) throws UnsupportedEncodingException {List<User> list = userMapper.list();XSSFWorkbook workbook = new XSSFWorkbook();XSSFSheet sheet = workbook.createSheet();XSSFRow row0 = sheet.createRow(0);row0.createCell(0).setCellValue("姓名");row0.createCell(1).setCellValue("地址");row0.createCell(2).setCellValue("密碼");row0.createCell(3).setCellValue("電話");for (int i = 0; i < list.size(); i++) {XSSFRow row = sheet.createRow(i + 1);XSSFCell cell = row.createCell(0);cell.setCellValue(list.get(i).getName());XSSFCell cell1 = row.createCell(1);cell1.setCellValue(list.get(i).getAddress());XSSFCell cell2 = row.createCell(2);cell2.setCellValue(list.get(i).getPassword());XSSFCell cell3 = row.createCell(3);cell3.setCellValue(list.get(i).getPhone());}response.setCharacterEncoding("UTF-8");//讓服務器告訴瀏覽器它發送的數據屬于什么文件類型response.setHeader("content-Type", "application/vnd.ms-excel");//當Content-Type 的類型為要下載的類型時 , 這個信息頭會告訴瀏覽器這個文件的名字和類型。response.setHeader("Content-Disposition","attachment;filename=" + URLEncoder.encode("b.xlsx", "UTF-8"));try {workbook.write(response.getOutputStream());} catch (IOException e) {e.printStackTrace();}}}

訪問接口：

成功下載：

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