EasyExcel合并单元格

需求

EasyExcel默认情况下写Excel是一行一行的，单元格不会自动合并，现在需求是合并这几列中相同的数据

思考

开始自己也不想做过多改动代码，经过阅读EasyExce官方文档和大量博客之后总结了一个通用的工具类，重写接口中的merge方法，然后自己在写入Excel的时候指定实体类属性以及对应的列就能实现功能

实现

/**
 * @author William.Shi
 * @date 2022/12/14
 * @description 自定义单元格合并策略
 */

public class CustomMergeStrategy extends AbstractMergeStrategy {

    /**
     * 分组，每几行合并一次
     */
    private List<Integer> exportFieldGroupCountList;

    /**
     * 目标合并列index
     */
    private Integer targetColumnIndex;

    // 需要开始合并单元格的首行index
    private Integer rowIndex;

    // exportDataList为待合并目标列的值
    public CustomMergeStrategy(List<String> exportDataList, Integer targetColumnIndex) {
        this.exportFieldGroupCountList = getGroupCountList(exportDataList);
        this.targetColumnIndex = targetColumnIndex;
    }


    @Override
    protected void merge(Sheet sheet, Cell cell, Head head, Integer relativeRowIndex) {

        if (null == rowIndex) {
            rowIndex = cell.getRowIndex();
        }
        // 仅从首行以及目标列的单元格开始合并，忽略其他
        if (cell.getRowIndex() == rowIndex && cell.getColumnIndex() == targetColumnIndex) {
            mergeGroupColumn(sheet);
        }
    }

    private void mergeGroupColumn(Sheet sheet) {
        int rowCount = rowIndex;
        for (Integer count : exportFieldGroupCountList) {
            if (count == 1) {
                rowCount  = count;
                continue;
            }
            // 合并单元格
            CellRangeAddress cellRangeAddress = new CellRangeAddress(rowCount, rowCount   count - 1, targetColumnIndex, targetColumnIndex);
            sheet.addMergedRegionUnsafe(cellRangeAddress);
            rowCount  = count;
        }
    }

    // 该方法将目标列根据值是否相同连续可合并，存储可合并的行数
    private List<Integer> getGroupCountList(List<String> exportDataList) {
        if (CollectionUtils.isEmpty(exportDataList)) {
            return new ArrayList<>();
        }

        List<Integer> groupCountList = new ArrayList<>();
        int count = 1;

        for (int i = 1; i < exportDataList.size(); i  ) {
            if (exportDataList.get(i).equals(exportDataList.get(i - 1))) {
                count  ;
            } else {
                groupCountList.add(count);
                count = 1;
            }
        }
        // 处理完最后一条后
        groupCountList.add(count);
        return groupCountList;
    }

}

这得益于EasyExcel中的这个接口

public abstract class AbstractMergeStrategy implements CellWriteHandler {
    @Override
    public void beforeCellCreate(WriteSheetHolder writeSheetHolder, WriteTableHolder writeTableHolder, Row row,
        Head head, Integer columnIndex, Integer relativeRowIndex, Boolean isHead) {

    }

    @Override
    public void afterCellCreate(WriteSheetHolder writeSheetHolder, WriteTableHolder writeTableHolder, Cell cell,
        Head head, Integer relativeRowIndex, Boolean isHead) {}

    @Override
    public void afterCellDataConverted(WriteSheetHolder writeSheetHolder,
        WriteTableHolder writeTableHolder, CellData cellData, Cell cell, Head head, Integer relativeRowIndex,
        Boolean isHead) {

    }

    @Override
    public void afterCellDispose(WriteSheetHolder writeSheetHolder, WriteTableHolder writeTableHolder,
        List<CellData> cellDataList, Cell cell, Head head, Integer relativeRowIndex, Boolean isHead) {
        if (isHead) {
            return;
        }
        merge(writeSheetHolder.getSheet(), cell, head, relativeRowIndex);
    }

    /**
     * merge
     *
     * @param sheet
     * @param cell
     * @param head
     * @param relativeRowIndex
     */
    protected abstract void merge(Sheet sheet, Cell cell, Head head, Integer relativeRowIndex);
}

我通过重写merge方法之后能实现这个需求，对应写Excel代码如下

 ExcelWriter excelWriter = EasyExcel.write(file).useDefaultStyle(false).build();
        WriteSheet sheet = EasyExcel.writerSheet("日报").head(AEDailyReport.class)
                .registerWriteHandler(new CustomMergeStrategy(AEDailyReportList.stream().map(AEDailyReport::getRegion)
                        .collect(Collectors.toList()), 1))
                .registerWriteHandler(new CustomMergeStrategy(AEDailyReportList.stream().map(i -> String.valueOf(i.getBudget()))
                        .collect(Collectors.toList()),4))
                .registerWriteHandler(new CustomMergeStrategy(AEDailyReportList.stream().map(i -> String.valueOf(i.getRemainingBudget()))
                        .collect(Collectors.toList()),9)).build();
        excelWriter.write(AEDailyReportList, sheet).finish();

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