pom依赖：

<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi-ooxml</artifactId>
    <version>5.2.5</version>
</dependency>

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>easyexcel</artifactId>
    <version>3.3.2</version>
</dependency>

替换核心代码：

public static InputStream onlineWriter(String fileType, InputStream inputStream, JSONObject model) throws Exception {

    ByteArrayOutputStream out = new ByteArrayOutputStream();

    try (ExcelWriter excelWriter = EasyExcel.write(out).withTemplate(inputStream)
            .registerWriteHandler(new CustomCellWeightWeightConfig())
            .registerWriteHandler(new CustomMergeStrategy())
            .build()) {

        // 设置自动换行，前提内容中需要加「\n」才有效
        WriteCellStyle writeCellStyle = new WriteCellStyle();
        writeCellStyle.setWrapped(true);

        HorizontalCellStyleStrategy cellStyleStrategy = new HorizontalCellStyleStrategy(null, writeCellStyle);
        WriteSheet writeSheet = EasyExcel.writerSheet().registerWriteHandler(cellStyleStrategy).build();

        excelWriter.fill(model, writeSheet);

        FillConfig fillConfig = FillConfig.builder().forceNewRow(Boolean.TRUE).build();
        for (Map.Entry<String, Object> entry : model.entrySet()) {
            if (entry.getValue() instanceof ArrayList) {
                JSONArray jsonArray = JSON.parseArray(JSONObject.toJSONString(entry.getValue()));
                FillWrapper fillWrapper = new FillWrapper(entry.getKey(), jsonArray);
                excelWriter.fill(fillWrapper, fillConfig, writeSheet);
            }
        }
        excelWriter.finish();
    }
    return new ByteArrayInputStream(out.toByteArray());
}

自定义调整行高策略：

/**
 * 填充内容包含\n换行符，重新计算行高
 */
public class CustomCellWeightWeightConfig extends AbstractColumnWidthStyleStrategy {

    private Map<Integer, Map<Integer, Integer>> CACHE = new HashMap<>();

    @Override
    protected void setColumnWidth(WriteSheetHolder writeSheetHolder, List<WriteCellData<?>> cellDataList, Cell cell, Head head, Integer relativeRowIndex, Boolean isHead) {

        boolean needSetWidth = isHead || StringUtils.isNotEmpty(cellDataList);
        if (needSetWidth) {
            //包含\n的内容修改行高
            String cellValue = getCellValue(cell);
            boolean contains =  StringUtils.contains(cellValue, ExcelTemplateUtil.WRAPPED);
            if (contains) {
                int rows = cellValue.split(ExcelTemplateUtil.WRAPPED).length;
                float height = cell.getRow().getHeightInPoints();
                cell.getRow().setHeightInPoints(rows * height);
            }
        }
    }

    public static String getCellValue(Cell cell) {
        String cellValue;
        switch (cell.getCellType()) {
            case STRING:
                cellValue = cell.getStringCellValue();
                break;
            case BOOLEAN:
                cellValue = String.valueOf(cell.getBooleanCellValue());
                break;
            case NUMERIC:
                cellValue = String.valueOf(cell.getNumericCellValue());
                break;
            default:
                cellValue = "";
                break;
        }
        return cellValue;
    }

}

自定义合并表格策略：

/**
 * 表格填充 每一列都赋值上一列的格式，确保列格式一致
 */
public class CustomMergeStrategy extends AbstractMergeStrategy {

    @Override
    protected void merge(Sheet sheet, Cell cell, Head head, Integer relativeRowIndex) {
        if(relativeRowIndex==null ||relativeRowIndex==0){
            return;
        }

        int rowIndex = cell.getRowIndex();
        int colIndex = cell.getColumnIndex();
        sheet=cell.getSheet();
        Row preRow = sheet.getRow(rowIndex - 1);
        Cell preCell = preRow.getCell(colIndex);//获取上一行的该格
        List<CellRangeAddress> list = sheet.getMergedRegions();
        for (int i = 0; i < list.size(); i++) {
            CellRangeAddress cellRangeAddress = list.get(i);
            if (cellRangeAddress.containsRow(preCell.getRowIndex()) && cellRangeAddress.containsColumn(preCell.getColumnIndex())) {
                int lastColIndex = cellRangeAddress.getLastColumn();
                int firstColIndex = cellRangeAddress.getFirstColumn();
                if (lastColIndex > firstColIndex) {

                    int lastRowIndex = cellRangeAddress.getLastRow();
                    CellRangeAddress cra = new CellRangeAddress(rowIndex, rowIndex, firstColIndex, lastColIndex);
                    sheet.addMergedRegion(cra);

                    //设置合并区域cra的边框
                    RegionUtil.setBorderBottom(BorderStyle.THIN, cra, sheet);
                    RegionUtil.setBorderLeft(BorderStyle.THIN, cra, sheet);
                    RegionUtil.setBorderRight(BorderStyle.THIN, cra, sheet);
                    RegionUtil.setBorderTop(BorderStyle.THIN, cra, sheet);
                    return;
                }
            }
        }
    }

}