设置EasyExcel自适应宽度

之前在使用easyexcel的时候在网络上抄了一个自适应excel宽度的源码，但是最近在另一个项目引入的时候导出excel发现报错了。更换了csdn的新版自适应宽度的源码之后发现正常了。

报错内容

The maximum column width for an individual cell is 255 characters.

报错源码

import com.alibaba.excel.enums.CellDataTypeEnum;
import com.alibaba.excel.metadata.CellData;
import com.alibaba.excel.metadata.Head;
import com.alibaba.excel.util.CollectionUtils;
import com.alibaba.excel.write.metadata.holder.WriteSheetHolder;
import com.alibaba.excel.write.style.column.AbstractColumnWidthStyleStrategy;
import org.apache.poi.ss.usermodel.Cell;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class ExcelWidthStyleStrategy extends AbstractColumnWidthStyleStrategy {


    private static final int MAX_COLUMN_WIDTH = 255;
    private  Map<Integer, Map<Integer, Integer>> CACHE = new HashMap(8);

    public ExcelWidthStyleStrategy() {
    }

    @Override
    protected void setColumnWidth(WriteSheetHolder writeSheetHolder, List<CellData> cellDataList, Cell cell, Head head, Integer relativeRowIndex, Boolean isHead) {
        boolean needSetWidth = isHead || !CollectionUtils.isEmpty(cellDataList);
        if (needSetWidth) {
            Map<Integer, Integer> maxColumnWidthMap = (Map)CACHE.get(writeSheetHolder.getSheetNo());
            if (maxColumnWidthMap == null) {
                maxColumnWidthMap = new HashMap(16);
                CACHE.put(writeSheetHolder.getSheetNo(), maxColumnWidthMap);
            }

            Integer columnWidth = this.dataLength(cellDataList, cell, isHead);
            if (columnWidth >= 0) {
                if (columnWidth > 255) {
                    columnWidth = 255;
                }

                Integer maxColumnWidth = (Integer)((Map)maxColumnWidthMap).get(cell.getColumnIndex());
                if (maxColumnWidth == null || columnWidth > maxColumnWidth) {
                    ((Map)maxColumnWidthMap).put(cell.getColumnIndex(), columnWidth);
                    writeSheetHolder.getSheet().setColumnWidth(cell.getColumnIndex(), columnWidth * 270);
                }

            }
        }
    }

    private Integer dataLength(List<CellData> cellDataList, Cell cell, Boolean isHead) {
        if (isHead) {
            return cell.getStringCellValue().getBytes().length;
        } else {
            CellData cellData = cellDataList.get(0);
            CellDataTypeEnum type = cellData.getType();
            if (type == null) {
                return -1;
            } else {
                switch(type) {
                    case STRING:
                        return cellData.getStringValue().getBytes().length;
                    case BOOLEAN:
                        return cellData.getBooleanValue().toString().getBytes().length;
                    case NUMBER:
                        return cellData.getNumberValue().toString().getBytes().length;
                    default:
                        return -1;
                }
            }
        }
    }
}

修改后的最新源码

import cn.hutool.core.collection.CollUtil;
import com.alibaba.excel.enums.CellDataTypeEnum;
import com.alibaba.excel.metadata.Head;
import com.alibaba.excel.metadata.data.CellData;
import com.alibaba.excel.metadata.data.WriteCellData;
import com.alibaba.excel.write.metadata.holder.WriteSheetHolder;
import com.alibaba.excel.write.style.column.AbstractColumnWidthStyleStrategy;
import org.apache.poi.ss.usermodel.Cell;

import java.util.HashMap;
import java.util.List;
import java.util.Map;


public class ExcelWidthStyleStrategy extends AbstractColumnWidthStyleStrategy {
    // excel列宽不能超过 255 * 255，因为要留出一点间距，所以设置最大为254
    private static final int MAX_COLUMN_WIDTH = 254;
    private Map<Integer, Map<Integer, Integer>> CACHE = new HashMap<>(8);
    
    /**
     * 设置列宽
     *
     * @param writeSheetHolder 书写页架
     * @param cellDataList     单元格数据列表
     * @param cell             细胞
     * @param head             头
     * @param relativeRowIndex 相对行索引
     * @param isHead           是头
     */
    protected void setColumnWidth(WriteSheetHolder writeSheetHolder, List<WriteCellData<?>> cellDataList, Cell cell, Head head, Integer relativeRowIndex, Boolean isHead) {
        boolean needSetWidth = isHead || !CollUtil.isEmpty(cellDataList);
        if (needSetWidth) {
            Map<Integer, Integer> maxColumnWidthMap = CACHE.get(writeSheetHolder.getSheetNo());
            if (maxColumnWidthMap == null) {
                maxColumnWidthMap = new HashMap<>(16);
                CACHE.put(writeSheetHolder.getSheetNo(), maxColumnWidthMap);
            }
            
            Integer columnWidth = this.dataLength(cellDataList, cell, isHead);
            if (columnWidth >= 0) {
                if (columnWidth > MAX_COLUMN_WIDTH) {
                    columnWidth = MAX_COLUMN_WIDTH;
                }
                Integer maxColumnWidth = maxColumnWidthMap.get(cell.getColumnIndex());
                if (maxColumnWidth == null || columnWidth > maxColumnWidth) {
                    maxColumnWidthMap.put(cell.getColumnIndex(), columnWidth);
                    // + 1 是为了让列的左右两边留出一点间距
                    writeSheetHolder.getSheet().setColumnWidth(cell.getColumnIndex(), (columnWidth + 1) * 256);
                }
            }
        }
    }
    
    /**
     * 数据长度
     *
     * @param cellDataList 单元格数据列表
     * @param cell         细胞
     * @param isHead       是头
     * @return {@link Integer }
     */
    private Integer dataLength(List<WriteCellData<?>> cellDataList, Cell cell, Boolean isHead) {
        if (isHead) {
            return cell.getStringCellValue().getBytes().length;
        } else {
            CellData cellData = cellDataList.get(0);
            CellDataTypeEnum type = cellData.getType();
            if (type == null) {
                return -1;
            } else {
                switch (type) {
                    case STRING:
                        return cellData.getStringValue().getBytes().length;
                    case BOOLEAN:
                        return cellData.getBooleanValue().toString().getBytes().length;
                    case NUMBER:
                        return cellData.getNumberValue().toString().getBytes().length;
                    default:
                        return -1;
                }
            }
        }
    }
}

使用阿里巴巴LongestMatchColumnWidthStyleStrategy

今天在找如何设置easyexcel单元格框线的时候看到了这么一篇文章：https://blog.csdn.net/catoop/article/details/144880735 ，发现原来easyexcel在最新版本已经将自适应宽度的源码收录到了仓库中，直接使用.registerWriteHandler(new LongestMatchColumnWidthStyleStrategy()) 就可以了 无需自己在项目中新建类实现