easyExcel导出
错误信息：

java.lang.IllegalStateException: Cannot add merged region C3:E3 to sheet because it overlaps with an existing merged region (B3:D3).

报表如上图所示，三级子表头有重复项，在使用easyExcel 1.1.1版本中会出现将三级子表头合并的情况
数据库导入情况如下
INSERT INTO `globle_item_config` (`field`,`column_zh`,`benable`,`checked`,`busi_id`,`sort`) VALUES ('orgName','组织','Y','Y','20','1');
INSERT INTO `globle_item_config` (`field`,`column_zh`,`benable`,`checked`,`busi_id`,`sort`) VALUES ('outputIncome','销项,开具增值税发票,不含税收入','Y','Y','20','2');
INSERT INTO `globle_item_config` (`field`,`column_zh`,`benable`,`checked`,`busi_id`,`sort`) VALUES ('outputTax','销项,开具增值税发票,税额','Y','Y','20','3');
INSERT INTO `globle_item_config` (`field`,`column_zh`,`benable`,`checked`,`busi_id`,`sort`) VALUES ('outputNoInvoicedIncome','销项,未开票收入,不含税收入','Y','Y','20','4');
INSERT INTO `globle_item_config` (`field`,`column_zh`,`benable`,`checked`,`busi_id`,`sort`) VALUES ('outputNoInvoicedTax','销项,未开票收入,税额','Y','Y','20','5');
INSERT INTO `globle_item_config` (`field`,`column_zh`,`benable`,`checked`,`busi_id`,`sort`) VALUES ('outputTotalIncome','销项,合计,不含税收入合计','Y','Y','20','6');
INSERT INTO `globle_item_config` (`field`,`column_zh`,`benable`,`checked`,`busi_id`,`sort`) VALUES ('outputTotalTax','销项,合计,税额合计','Y','Y','20','7');
INSERT INTO `globle_item_config` (`field`,`column_zh`,`benable`,`checked`,`busi_id`,`sort`) VALUES ('outputTotalAmount','销项,合计,价税合计','Y','Y','20','8');

INSERT INTO `globle_item_config` (`field`,`column_zh`,`benable`,`checked`,`busi_id`,`sort`) VALUES ('subInitial','分包,期初留抵','Y','Y','20','9');
INSERT INTO `globle_item_config` (`field`,`column_zh`,`benable`,`checked`,`busi_id`,`sort`) VALUES ('subTotalAmount','分包,分包发生额','Y','Y','20','10');
INSERT INTO `globle_item_config` (`field`,`column_zh`,`benable`,`checked`,`busi_id`,`sort`) VALUES ('subAdjustiveNum','分包,调整数','Y','Y','20','11');
INSERT INTO `globle_item_config` (`field`,`column_zh`,`benable`,`checked`,`busi_id`,`sort`) VALUES ('subRealTotalAmount','分包,实际抵扣分包含税金额','Y','Y','20','12');
INSERT INTO `globle_item_config` (`field`,`column_zh`,`benable`,`checked`,`busi_id`,`sort`) VALUES ('subRealTax','分包,实际抵扣分包税额','Y','Y','20','13');
INSERT INTO `globle_item_config` (`field`,`column_zh`,`benable`,`checked`,`busi_id`,`sort`) VALUES ('subLastAmount','分包,期未留抵数','Y','Y','20','14');

导出数据时会报错：

java.lang.IllegalStateException: Cannot add merged region C3:E3 to sheet because it overlaps with an existing merged region (B3:D3).
考虑到是因为


销项一级子表头下的三级子表头有重复项，会被自动合并，合并过程中，因为“开具增值税发票”单元格已经合并，所以“税额”项在合并单元格时就报错了
解决方案：

方案1. 将相同的列名改成不一样的，这样就可以达到想要的合并单元格的效果。 缺点：可能导出的列名并不是自己想要的。

方案2. 为了与页面上列名保持一致，就尝试的升级了easyExcel的版本，结果测试了一下，就OK了。将版本从1.1.1升级到2.0.5版本
附上测试代码：
private static byte[] getFileBytes(List<List<String>> easyData) {
    ByteArrayOutputStream out = new ByteArrayOutputStream();
    ExcelWriter writer = new ExcelWriter(out, ExcelTypeEnum.XLSX);
    Sheet sheet = new Sheet(1, 0);

    Table table = new Table(1);
    List<List<String>> head = new ArrayList<>();
    //提取表头
    List<String> headNames = easyData.get(0);
    headNames.forEach(headName -> {
      List<String> headCoulumn = new ArrayList<>();
      String[] headStr = headName.split(",");
      if(headStr != null) {
        for (String str : headStr) {
          headCoulumn.add(str);
        }
      }
      head.add(headCoulumn);
    });
    table.setHead(head);
    //提取数据并写入流
    writer.write0(easyData.subList(1, easyData.size()), sheet, table);
    writer.finish();
    byte[] bytes = out.toByteArray();
    return bytes;
  }

  public static void main(String[] args) throws IOException {

    List<List<String>> exc = new ArrayList<>();
    List<String> rows = new ArrayList<>();
    rows.add("组织");
    rows.add("销项,开具增值税发票,不含税收入");
    rows.add("销项,开具增值税发票,税额");
    rows.add("销项,未开票收入,不含税收入");
    rows.add("销项,未开票收入,税额");
    rows.add("销项,合计,不含税收入合计");
    rows.add("销项,合计,税额合计");
    rows.add("销项,合计,价税合计");
    rows.add("分包,期初留抵");
    rows.add("分包,分包发生额");
    rows.add("进项,期初留抵");
    exc.add(rows);
    for(int i = 0; i < 3; i++){
      List<String> rowsValue = new ArrayList<>();
      rowsValue.add("组织名称"+i);
      rowsValue.add(String.valueOf(2+i));
      rowsValue.add(String.valueOf(2+i));
      rowsValue.add(String.valueOf(2+i));
      rowsValue.add(String.valueOf(2+i));
      rowsValue.add(String.valueOf(2+i));
      rowsValue.add(String.valueOf(2+i));
      rowsValue.add(String.valueOf(2+i)i);
      rowsValue.add(String.valueOf(2+i));
      rowsValue.add(String.valueOf(2+i));
      exc.add(rowsValue);
    }
    byte[] b = getFileBytes(exc);
    FileUtils.writeByteArrayToFile(new File("D:\\tmp\\testMuliteHead..xlsx"), b);
  }

导入依赖
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>easyexcel</artifactId>
    <version>2.1.6</version>
</dependency>

导出
Controller
import javax.servlet.http.HttpServletResponse;

/**
 * 导出数据
 * @param response response
 * @return result
 * @author liu
 */
@GetMapping("exportExcelData")
public Result exportExcelData(HttpServletResponse response) {
    service.exportExcelData(response);  
    return Result.ok();
}

Service
import javax.servlet.http.HttpServletResponse;

/**
 * 导出数据
 * @param response response
 * @author liu
 */
 void exportExcelData(HttpServletResponse response);

ServiceImpl
import javax.servlet.http.HttpServletResponse;

@Override
public void exportExcelData(HttpServletResponse response) {
    String fileName = "数据信息";
	String sheetName = "数据信息";
	/**  数据库查询数据并处理 */
	List<ExcelData> dataList = mapper.exportExcelData(); //返回数据信息
	
	List<ExcelData> list = new ArrayList<>();
    
    for (ExcelData excelData : dataList) {
		ExcelData excelPlanData = ExcelData.builder()
		        .id(excelData.getId)
		        .name(excelData.getName)
		        .age(excelData.getAge)
		        .sex(excelData.getSex).build();
		list.add(excelPlanData);
    }
    try {
    	ExcelUtil.writeExcel(response,list,fileName,sheetName,ExcelData.class);	
    } catch (Exception e) {
    	e.printStackTrace();	
    }
	
}

Model
import com.alibaba.excel.annotation.ExcelProperty;
import lombok.Builder;
import lombok.Data;

/**
 * 数据导出实体类
 * @author liu
 */
@Data
@Builder
public class ExcelData {
	
	/**
	 * id
	 */
	//导出的Excel标头信息，以及所在第几列
	@ExcelProperty(value = "id", index = 0)  
	private Integer id;

	/**
	 * 姓名
	 */
	@ExcelProperty(value = "姓名", index = 1) 
	private String name;

	/**
	 * 年龄
	 */
	@ExcelProperty(value = "年龄", index = 2) 
	private Integer age;

	/**
	 * 性别
	 */
    @ExcelProperty(value = "性别", index = 3) 
	private String sex;
}

ExcelUtil
import com.alibaba.excel.EasyExcel;
import com.alibaba.excel.support.ExcelTypeEnum;
import com.alibaba.excel.write.metadata.style.WriteCellStyleStrategy;

import java.io.OutputStream;
import java.net.URLEncoder;
import java.util.List;

import javax.servlet.http.HttpServletResponse;
import org.apache.poi.ss.usermodel.HorizontalAlignment;

/**
 * 导出工具类
 * @author liu
 */
public class ExcelUtil {
	
    /**
	 * 导出
	 * @param response response
	 * @param data data
	 * @param fileName fileName
	 * @param sheetName sheetName
	 * @param clazz clazz
     */
    public static void writeExcel(HttpServletResponse response,List<? extends Object> data, 
            String fileName,String sheetName,Class clazz) {
        //表头样式
        WriteCellStyle headWriteCellStyle = new WriteCellStyle();
 		//设置表头居中对齐
 		headWriteCellStyle.setHorizontalAlignment(HorizontalAlignment.CENTER);
 		//内容样式
 		WriteCellStyle contentWriteCellStyle = new WriteCellStyle();
 		//设置内容靠左对齐
 		contentWriteCellStyle.setHorizontalAlignment(HorizontalAlignment.LEFT);
 		HorizontalCellStyleStrategy horizontalCellStyleStrategy = 
 		        new HorizontalCellStyleStrategy(headWriteCellStyle,contentWriteCellStyle);
 		try {
		    EasyExcel.write(getOutputStream(fileName,response),clazz)
		 	        .excelType(ExcelTypeEnum.XLSX)
		 	        .sheet(sheetName)
		 	        .registerWriteHandler(horizontalCellStyleStrategy)
		 	        .doWrite(data);
		} catch (Exception e) {
		    e.printStackTrace();
		}
    }
    
    /**
     * 格式
     * @param fileName fileName
     * @param response response
     * @throws Exception exception
     * @author liu
     * @return java.io.OutputStream 
     */ 
    private static OutputStream getOutputStream(String fileName,HttpServletResponse response) throws Exception {
        fileName = URLEncoder.encode(fileName,"UTF-8");
        response.setContentType("application/vnd.ms-excel");
        response.setCharacterEncoding("utf8");
        response.setHeader("Content-Disposition", "attachment;filename=" + ".xlsx");
        return response.getOutputStream();
    }
}

需要添加的jar包：
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>easyexcel</artifactId>
    <version>2.1.6</version>
</dependency>

导出的controller代码实现：
package com.ruoyi.web.controller.export;

import com.alibaba.excel.EasyExcel;
import com.google.common.collect.Lists;
import com.ruoyi.web.controller.demo.domain.UserOperateModel;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.net.URLEncoder;
import java.text.SimpleDateFormat;
import java.util.Date;

@Controller
@RequestMapping("/download")
public class Export {
    private static final SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

	//第一种导出
    @GetMapping("/download")
    public void download(HttpServletResponse response) throws IOException {
        // 这里注意 有同学反应使用swagger 会导致各种问题，请直接用浏览器或者用postman
        response.setContentType("application/vnd.ms-excel");
        response.setCharacterEncoding("utf-8");
        // 这里URLEncoder.encode可以防止中文乱码 当然和easyexcel没有关系
        String fileName = URLEncoder.encode("测试", "UTF-8");
        response.setHeader("Content-disposition", "attachment;filename=" + fileName + ".xlsx");
        EasyExcel.write(response.getOutputStream(), UserOperateModel.class).sheet("模板").doWrite(Lists.newArrayList());
    }
	//第二种导出
    @GetMapping("/downloads")
    public void downloads(HttpServletResponse response) throws IOException {
        String fileName = "黑名单导入模板_" + sdf.format(new Date()) + ".xls";
        response.setHeader("Content-disposition",
                "attachment;filename=" + new String(fileName.getBytes("gb2312"), "ISO8859-1"));// 设置文件头编码格式
        response.setContentType("APPLICATION/OCTET-STREAM;charset=UTF-8");// 设置类型
        response.setHeader("Cache-Control", "no-cache");// 设置头
        response.setDateHeader("Expires", 0);// 设置日期头
        response.setHeader("Content-disposition", "attachment;filename=" + fileName + ".xlsx");
        EasyExcel.write(response.getOutputStream(), UserOperateModel.class).sheet("模板").doWrite(Lists.newArrayList());
    }
}

实体类:
	/**
     * 忽略这个字段
     */
    @ExcelIgnore
    private int userId;

    @ExcelProperty("用户编号")
    private String userCode;
    @ExcelProperty("用户姓名")
    private String userName;

    @ExcelProperty("用户性别")
    private String userSex;
    @ExcelProperty("用户手机")
    private String userPhone;

    @ExcelIgnore
    private String userEmail;

    @ExcelIgnore
    private double userBalance;

    @ExcelIgnore
    private String status;

    @ExcelIgnore
    private Date createTime;

导出的效果：

EasyExcel导出excel
1.首先建立一个实体类
public class ExcelMode extends BaseRowModel {
    @ExcelIgnore   //excel中不导出字段
    private Integer id;
    @ExcelProperty(value = "姓名" ,index = 0)
    private String name;
    @ExcelProperty(value = "密码" ,index = 1)
    private String password;
    @ExcelProperty(value = "手机号码",index = 2)
    private String phone;
    @ExcelProperty(value = "性别",index = 2,converter = SettlementConverter.class )
     //SettlementConverter.class 将数据库枚举字段转换成字符串类型（例：1/男，2/女
    private Integer sex;


    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }

    public Integer getSex() {
        return sex;
    }

    public void setSex(Integer sex) {
        this.sex = sex;
    }
}


SettlementConverter.class 实现 Converter 接口

public class SettlementConverter implements Converter<Integer> {

    @Override
    public Class supportJavaTypeKey() {
        return null;
    }

    @Override
    public CellDataTypeEnum supportExcelTypeKey() {
        return null;
    }

    @Override
    public Integer convertToJavaData(CellData cellData, ExcelContentProperty excelContentProperty, GlobalConfiguration globalConfiguration) throws Exception {
        return null;
    }

    @Override
    public CellData convertToExcelData(Integer s, ExcelContentProperty excelContentProperty, GlobalConfiguration globalConfiguration) throws Exception {
        if(s == 1){
            return new CellData("男");
        }else {
            return new CellData("女");
        }
    }


导出excel

    @RequestMapping(value = "/toExcel")
	@ResponseBody
	public Object toExcel(HttpServletRequest rep , HttpServletResponse reps) {
		try {
			ExcelMode u = new ExcelMode();
			
			List<ExcelMode> list = userservice.ExcelMode();
			String fileName = new String("文件名称.xlsx".getBytes(), "ISO-8859-1");
			reps.addHeader("Content-Disposition", "filename=" + fileName);
			ServletOutputStream out = reps.getOutputStream();
			EasyExcelFactory.write(out, ExcelMode.class).sheet("文件标签名称").doWrite(list);
		}catch (Exception e){
			e.printStackTrace();
		}
		return null;
	}