SpringBoot----EasyExcel依赖下载Excel文件

		
			com.alibaba
			easyexcel
			3.0.5
		

@Override
    public void goodsInfoDownload() {
        List list=goodsMapper.selectGoodsInfo();
        SimpleDateFormat formatter= new SimpleDateFormat("yyyyMMdd");
        Date date = new Date(System.currentTimeMillis());
        String excelName1=formatter.format(date)+"商品明细.xlsx";
          String excelName="H:\"+excelName1;

        ExcelWriter excelWriter=null;
        try {
            excelWriter=EasyExcel
            				.write(excelName,GoodsInfoDto.class)
            				//这个是我自己写的一个类，主要用来限制excel的列宽在5~30之间（方法在下面），这个可以不要
            				.registerWriteHandler(new MyExcelHandler())
            				.build();
            WriteSheet writeSheet=EasyExcel.writerSheet("goods").build();
            excelWriter.write(list,writeSheet);
        } finally {
            if (excelWriter!=null){
                excelWriter.finish();
            }
        }
    }

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.commons.collections4.CollectionUtils;
import org.apache.poi.ss.usermodel.Cell;

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

public class MyExcelHandler extends AbstractColumnWidthStyleStrategy {

    private static final int MAX_COLUMN_WIDTH = 30;
    //因为在自动列宽的过程中，有些设置地方让列宽显得紧凑，所以做出了个判断
    private static final int MIN_COLUMN_WIDTH = 5;
    private  Map> CACHE = new HashMap(8);

    public void Custemhandler() {
    }

    @Override
    protected void setColumnWidth(WriteSheetHolder writeSheetHolder, List> cellDataList, Cell cell, Head head, Integer relativeRowIndex, Boolean isHead) {
        boolean needSetWidth = isHead || !CollectionUtils.isEmpty(cellDataList);
        if (needSetWidth) {
            Map 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 > MAX_COLUMN_WIDTH) {
                    columnWidth = MAX_COLUMN_WIDTH;
                }else {
                    if(columnWidth
                        columnWidth =MIN_COLUMN_WIDTH;
                    }
                }

                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* 256);
                }
            }
        }
    }

    private  Integer dataLength(List> cellDataList, Cell cell, Boolean isHead) {
        if (isHead) {
            return cell.getStringCellValue().getBytes().length;
        } else {
            CellData 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;
                }
            }
        }
    }


}

参考文章：https://blog.csdn.net/weixin_44811578/article/details/107101248?spm=1001.2014.3001.5506