【EasyExcel】封裝一個分頁寫數據的通用方法，有效規避OOM

通過SQL查詢出來一次性寫，在大數據量時存在OOM的隱患
分頁查詢、分批次寫數據，避免導出大數據量時內存消耗陡增
基於mybatis-puls分頁查詢

example

導出250萬用戶數據，代碼看起來是不是很清爽呢？

@Test
public void pageWrite() {
   // build excel writer
   ExcelWriter excelWriter = EasyExcel.write("E:/easyexcel/testPageWrite.xlsx", PageWriteData.class).excelType(ExcelTypeEnum.XLSX).build();
   // page write
   EasyExcelUtils.pageWrite(excelWriter, "數據清單", 2_500_000L,
           (currentPage, pageSize) -> {
       			Page<User> page = new Page<>(currentPage, pageSize);
              	return userService.selectByPage(page).getRecords();
           });
}

源碼實現

EasyExcelUtils.java

package com.itplh.common.util;

import com.itplh.base.service.MybatisPlusPageQueryService;
import com.itplh.common.constant.ExcelPageEnum;
import com.alibaba.excel.EasyExcel;
import com.alibaba.excel.ExcelWriter;
import com.alibaba.excel.support.ExcelTypeEnum;
import com.alibaba.excel.write.metadata.WriteSheet;

/**
 * @description:
 * @author: tanpeng
 * @date: 2020-02-28 10:46
 * @version: v1.0.0
 */
public class EasyExcelUtils extends EasyExcel {

    /**
     * @description: 分頁查詢、分批次寫數據，避免導出大數據量時OOM
     * auto close resource
     * @author: tanpeng
     * @date : 2020-02-28 11:42
     * @version: v1.0.0
     * @param excelWriter
     * @param sheetName
     * @param totalCount 數據總數
     * @param pageQueryService
     */
    public static void pageWrite(ExcelWriter excelWriter,
                                  String sheetName,
                                  long totalCount,
                                  MybatisPlusPageQueryService pageQueryService) {

        // default export xlsx, page size 10000, sheet max row 1000000
        int pageSize = ExcelPageEnum.XLSX.getPageSize();
        int sheetMaxRow = ExcelPageEnum.XLSX.getSheetMaxRow();

        ExcelTypeEnum excelType = excelWriter.writeContext().writeWorkbookHolder().getExcelType();
        boolean isXls =  excelType != null && ExcelTypeEnum.XLS.getValue().equals(excelType.getValue());
        if (isXls) {
            pageSize = ExcelPageEnum.XLS.getPageSize();
            sheetMaxRow = ExcelPageEnum.XLS.getSheetMaxRow();
        }

        // compute page count, sheet count
        long pageCount = (totalCount - 1) / pageSize + 1;
        long sheetCount = (totalCount - 1) / sheetMaxRow + 1;
        int currentPage = 0;

        // page write data
        WriteSheet sheet = null;
        for (int i = 0; i < sheetCount; i++) {
            sheet = EasyExcel.writerSheet(i, sheetName + i).build();
            for (int j = 0; j < (sheetMaxRow / pageSize); j++) {
                // must use ++currentPage, mybatis-plus page query current page start 1
                excelWriter.write(pageQueryService.data(++currentPage, pageSize), sheet);
                if (currentPage >= pageCount) {
                    break;
                }
            }
        }

        // close source
        excelWriter.finish();
    }

}

MybatisPlusPageQueryService.java

package com.itplh.base.service;

import java.util.List;

/**
 * @description:
 * @author: tanpeng
 * @date: 2020-02-28 11:20
 * @version: v1.0.0
 */
@FunctionalInterface
public interface MybatisPlusPageQueryService<E> {

    /**
     * @description: 獲取分頁查詢數據
     * 注意：mybatis-plus 的 current 參數是從 1 開始
     * @author: tanpeng
     * @date : 2020-02-28 12:08
     * @version: v1.0.0
     * @param current 當前頁，從 1 開始
     * @param size
     */
    List<E> data(int current, int size);

}

ExcelPageEnum.java

package com.itplh.common.constant;

/**
 * @description: excel 分頁參數枚舉
 * @author: tanpeng
 * @date: 2020-02-28 11:29
 * @version: v1.0.0
 */
public enum ExcelPageEnum {

    XLS(10_000, 60_000),
    XLSX(10_000, 1_000_000);

    private int pageSize;
    private int sheetMaxRow;

    ExcelPageEnum(int pageSize, int sheetMaxRow) {
        this.pageSize = pageSize;
        this.sheetMaxRow = sheetMaxRow;
    }

    public int getPageSize() {
        return pageSize;
    }

    public int getSheetMaxRow() {
        return sheetMaxRow;
    }
}