springbootはpoiを使ってデータの導出過程を詳しく説明します。

<!--poi-->
    <dependency>
      <groupId>org.apache.xmlbeans</groupId>
      <artifactId>xmlbeans</artifactId>
      <version>2.6.0</version>
    </dependency>
    <dependency>
      <groupId>dom4j</groupId>
      <artifactId>dom4j</artifactId>
      <version>1.6.1</version>
    </dependency>
    <dependency>
      <groupId>org.apache.poi</groupId>
      <artifactId>poi</artifactId>
      <version>3.9</version>
    </dependency>
    <dependency>
      <groupId>org.apache.poi</groupId>
      <artifactId>poi-ooxml</artifactId>
      <version>3.9</version>
    </dependency>
    <!--poi-->

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
 
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
 
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.CellStyle;
import org.apache.poi.ss.usermodel.Font;
import org.apache.poi.ss.usermodel.IndexedColors;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;
 
/**
 * @author qingmu
 * @version     ：2017 12 28    4:53:29
 *    : POI     
 */
public class ExportPOIUtils {
 
  //    : fileName：     projects：     columnNames：     keys： map  key
  public static void start_download(HttpServletResponse response, String fileName, List<?> projects,
      String[] columnNames, String[] keys) throws IOException {
     
    //              List<Map<String,Object>>
    List<Map<String,Object>> list=createExcelRecord(projects, keys);
 
    ByteArrayOutputStream os = new ByteArrayOutputStream();
    try {
      //     Workbook         
      createWorkBook(list,keys,columnNames).write(os);
    } catch (IOException e) {
      e.printStackTrace();
    }
    byte[] content = os.toByteArray();
    InputStream is = new ByteArrayInputStream(content);
    //   response  ，        
    response.reset();
    response.setContentType("application/vnd.ms-excel;charset=utf-8");
    response.setHeader("Content-Disposition", "attachment;filename="+ new String((fileName + ".xls").getBytes(), "iso-8859-1"));
    ServletOutputStream out = response.getOutputStream();
    BufferedInputStream bis = null;
    BufferedOutputStream bos = null;
    try {
      bis = new BufferedInputStream(is);
      bos = new BufferedOutputStream(out);
      byte[] buff = new byte[2048];
      int bytesRead;
      while (-1 != (bytesRead = bis.read(buff, 0, buff.length))) {
        bos.write(buff, 0, bytesRead);
      }
    } catch (final IOException e) {
      throw e;
    } finally {
      if (bis != null)
        bis.close();
      if (bos != null)
        bos.close();
    }
  }
   
  private static List<Map<String, Object>> createExcelRecord(List<?> projects, String[] keys) {
    List<Map<String, Object>> listmap = new ArrayList<Map<String, Object>>();
    Map<String, Object> map = new HashMap<String, Object>();
    map.put("sheetName", "sheet");
    listmap.add(map);
    Object project=null;
    for (int j = 0; j < projects.size(); j++) {
      project=projects.get(j);
      Map<String, Object> mapValue = new HashMap<String, Object>();
      for(int i=0; i<keys.length; i++){
        mapValue.put(keys[i], getFieldValueByName(keys[i], project));
      }
 
      listmap.add(mapValue);
    }
    return listmap;
  }
  /**
   *                
   * */ 
  private static Object getFieldValueByName(String fieldName, Object o) { 
    try {  
      String firstLetter = fieldName.substring(0, 1).toUpperCase();  
      String getter = "get" + firstLetter + fieldName.substring(1);  
      Method method = o.getClass().getMethod(getter, new Class[] {});  
      Object value = method.invoke(o, new Object[] {});  
      return value;  
    } catch (Exception e) {  
      e.printStackTrace(); 
      return null;  
    }  
  }
  /**
   *   excel    
   * @param keys list map key    
   * @param columnNames excel   
   * */
  private static Workbook createWorkBook(List<Map<String, Object>> list,String []keys,String columnNames[]) {
    //   excel   
    Workbook wb = new HSSFWorkbook();
    //      sheet（ ），   
    Sheet sheet = wb.createSheet(list.get(0).get("sheetName").toString());
    //       。             ；，           ，n       。
    for(int i=0;i<keys.length;i++){
      sheet.setColumnWidth((short) i, (short) (35.7 * 150));
    }
 
    //      
    Row row = sheet.createRow((short) 0);
 
    //          
    CellStyle cs = wb.createCellStyle();
    CellStyle cs2 = wb.createCellStyle();
 
    //       
    Font f = wb.createFont();
    Font f2 = wb.createFont();
 
    //          （    ）
    f.setFontHeightInPoints((short) 10);
    f.setColor(IndexedColors.BLACK.getIndex());
    f.setBoldweight(Font.BOLDWEIGHT_BOLD);
 
    //          （   ）
    f2.setFontHeightInPoints((short) 10);
    f2.setColor(IndexedColors.BLACK.getIndex());
 
    //            （    ）
    cs.setFont(f);
    cs.setBorderLeft(CellStyle.BORDER_THIN);
    cs.setBorderRight(CellStyle.BORDER_THIN);
    cs.setBorderTop(CellStyle.BORDER_THIN);
    cs.setBorderBottom(CellStyle.BORDER_THIN);
    cs.setAlignment(CellStyle.ALIGN_CENTER);
 
    //            （   ）
    cs2.setFont(f2);
    cs2.setBorderLeft(CellStyle.BORDER_THIN);
    cs2.setBorderRight(CellStyle.BORDER_THIN);
    cs2.setBorderTop(CellStyle.BORDER_THIN);
    cs2.setBorderBottom(CellStyle.BORDER_THIN);
    cs2.setAlignment(CellStyle.ALIGN_CENTER);
    //    
    for(int i=0;i<columnNames.length;i++){
      Cell cell = row.createCell(i);
      cell.setCellValue(columnNames[i]);
      cell.setCellStyle(cs);
    }
    //        
    for (short i = 1; i < list.size(); i++) {
      // Row  ,Cell    , Row   Cell    0     
      //     ，  sheet 
      Row row1 = sheet.createRow((short) i);
      //  row        
      for(short j=0;j<keys.length;j++){
        Cell cell = row1.createCell(j);
        cell.setCellValue(list.get(i).get(keys[j]) == null?" ": list.get(i).get(keys[j]).toString());
        cell.setCellStyle(cs2);
      }
    }
    return wb;
  }
}

import com.example.uploaddemo.util.ExportPOIUtils;
import org.springframework.web.bind.annotation.RequestMapping;

import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

/**
 * @author qingmu
 * @date 
 */
public class UserController {
  @RequestMapping("exportList")
  public void exportList(HttpServletResponse response, String ids) {

    String fileName = "      ";

    List<User> users = new ArrayList<User>();

    //   
    String columnNames[] = {"ID", "  ", "  ", "    ", "    ", "  ",
        "  ", "  ", "  /  ", "  /    ", "    ", "    "};
    // map  key
    String keys[] = {"id", "userName", "gender", "dept", "unit", "email",
        "tel", "phone", "degree", "major", "parentName", "isLocked"};
    try {
      ExportPOIUtils.start_download(response, fileName, users, columnNames, keys);
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
}