EasyExcel分页写入工具类

1. 相关依赖 pom.xml

  
    com.baomidou
    mybatis-plus-boot-starter
    3.4.2
  

  
    cn.hutool
    hutool-all
    5.5.7
  

  
    com.alibaba
    easyexcel
    3.0.5
  

  
    org.apache.commons
    commons-collections4
    4.4
  

2. EasyExcelWriteUtils

import cn.hutool.core.util.PageUtil;
import com.alibaba.excel.ExcelWriter;
import com.alibaba.excel.write.metadata.WriteSheet;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.baomidou.mybatisplus.extension.service.IService;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.function.BiFunction;
import java.util.function.Function;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.collections4.CollectionUtils;
import org.springframework.beans.BeanUtils;

/**
 * EasyExcel写入工具类
 *
 * @author firefly_
 * @since 2021/12/26
 */
@Slf4j
public class EasyExcelWriteUtils {

  private EasyExcelWriteUtils() {
  }

  /**
   * 分页写入
   *
   * @param dao dao extends IService
   * @param countFunction 查询总数的方法
   * @param queryFunction 分页查询的方法
   * @param pageSize 分页大小
   * @param excelWriter writer
   * @param writeSheet sheet
   * @param headClass 导出文件表头类
   * @param 
   * @param 
   */
  public static , T> void pageWrite(S dao,
      Function countFunction, BiFunction, ?> queryFunction,
      Integer pageSize, ExcelWriter excelWriter, WriteSheet writeSheet, Class headClass) {

    // 查询数据总数
    Integer totalCount = countFunction.apply(dao);
    if (null == totalCount || 0 == totalCount) {
      // 写入空数据到sheet
      excelWriter.write(new ArrayList<>(), writeSheet);
      return;
    }

    // 计算总页数
    int totalPage = PageUtil.totalPage(totalCount, pageSize);
    IntStream.rangeClosed(1, totalPage).boxed()
        .forEach(e -> {
          List data = new ArrayList<>();

          // 执行分页查询，返回类型可能是List，可能是Page
          Object result = queryFunction.apply(dao, new Page<>(e, pageSize, false));
          if (result.getClass().equals(ArrayList.class)) {
            // 转换成表头类
            data = copyList((List) result, headClass);
          } else if (result.getClass().equals(Page.class)) {
            // 转换成表头类
            data = copyList(((Page) result).getRecords(), headClass);
          }
          // 执行写入
          excelWriter.write(data, writeSheet);
        });
    // 如果是往同一个文件写入多个sheet，这一步操作放在方法外面
    excelWriter.finish();
  }

  /**
   * 对象属性复制
   *
   * @param sourceObj
   * @param targetCls
   * @param 
   * @return
   */
  private static  T copyBean(Object sourceObj, Class targetCls) {
    T targetObj = null;
    if (sourceObj != null) {
      try {
        targetObj = targetCls.newInstance();
        BeanUtils.copyProperties(sourceObj, targetObj);
      } catch (Exception e) {
        e.printStackTrace();
      }
    }
    return targetObj;
  }

  /**
   * 集合属性复制
   *
   * @param list
   * @param targetCls
   * @param 
   * @param 
   * @return
   */
  private static  List copyList(Collection list, Class targetCls) {
    if (CollectionUtils.isEmpty(list)) {
      return new ArrayList<>();
    }

    return list.stream().map(obj -> copyBean(obj, targetCls))
        .collect(Collectors.toList());
  }

}