easyexcel 自动设置列宽(转)

来源：oschina

链接：https://my.oschina.net/u/3574106/blog/4287753

　　　　<dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>easyexcel</artifactId>
            <version>2.1.4</version>
        </dependency>

导出controller层代码

 @RequestMapping("/download")
    public void download(HttpServletResponse response) throws IOException {

        response.setContentType("application/vnd.ms-excel");
        response.setCharacterEncoding("utf-8");

        String fileName = URLEncoder.encode("测试", "UTF-8");
        response.setHeader("Content-disposition", "attachment;filename=" + fileName + ".xlsx");
        List<Dept> depts = new ArrayList<>(3);
        for (int i = 0; i < 3; i++) {
            Dept dept = new Dept();
            dept.setDname("d"+i);
            dept.setDeptno(i);
            dept.setDbDource("s"+i);
            dept.setEmpname("0000000000000000000000000000000000000000000e"+i);
            depts.add(dept);
        }
        EasyExcel.write(response.getOutputStream(), Dept.class)
                .head(Dept.class).registerWriteHandler(new CustomCellWriteHandler())
                .sheet("模板").doWrite(depts);
    }

dept

import com.alibaba.excel.annotation.ExcelProperty;

public class Dept {
    @ExcelProperty(value = "部门编号")
    private Integer deptno;
    @ExcelProperty(value = "部门名称")
    private String dname;
    @ExcelProperty(value = "部门来源")
    private String dbDource;
    @ExcelProperty(value = "员工名")
    private String empname;
// 省略get/set

writeHandler

package com.example.springbootbasic.config;

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 org.slf4j.Logger;
import org.slf4j.LoggerFactory;

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

public class CustomCellWriteHandler extends AbstractColumnWidthStyleStrategy {

    private static final Logger LOGGER = LoggerFactory.getLogger(CustomCellWriteHandler.class);

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

    @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 = CACHE.get(writeSheetHolder.getSheetNo());
            if (maxColumnWidthMap == null) {
                maxColumnWidthMap = new HashMap<>();
                CACHE.put(writeSheetHolder.getSheetNo(), maxColumnWidthMap);
            }

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

                Integer maxColumnWidth = maxColumnWidthMap.get(cell.getColumnIndex());
                if (maxColumnWidth == null || columnWidth > maxColumnWidth) {
                    maxColumnWidthMap.put(cell.getColumnIndex(), columnWidth);
                    writeSheetHolder.getSheet().setColumnWidth(cell.getColumnIndex(), columnWidth * 256);
                }

            }
        }
    }

    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;
                }
            }
        }
    }
}