Easyexcel 导出数据 一对多关系导出数据集合

客户要求

要求导出的表格如图

实现这样表格 很多人会想到动态表头，easypoi可以直接实现，但是我用的是easyexcel,而easyexcel自身并没有提供自动合并的功能所以还是需要自己来合并。

代码如下

首先我们来看下将嵌套数据平铺，不进行合并导出的Excel

实现思路

首先我们得把原来嵌套的订单商品信息给平铺了，创建一个专门的导出对象OrderData，包含订单和商品信息，二级表头可以通过设置@ExcelProperty的value为数组来实现

@Data
@AllArgsConstructor
@NoArgsConstructor
public class OrderData {


    @ExcelProperty(value = "订单编码")
    @ColumnWidth(20)
    @CollectCustomMerge(needMerge = true, isPk = true)
    private String orderSn;
    @ExcelProperty(value = "创建时间")
    @ColumnWidth(20)
    @DateTimeFormat("yyyy-MM-dd")
    @CollectCustomMerge(needMerge = true)
    private Date createTime;
    @ExcelProperty(value = "收货地址")
    @CollectCustomMerge(needMerge = true)
    @ColumnWidth(20)
    private String receiverAddress;
    @ExcelProperty(value = {"商品信息", "商品编码"})
    @ColumnWidth(20)
    private String productSn;
    @ExcelProperty(value = {"商品信息", "商品名称"})
    @ColumnWidth(20)
    private String name;
    @ExcelProperty(value = {"商品信息", "商品标题"})
    @ColumnWidth(30)
    private String subTitle;

}

创建一个自定义注解CollectCustomMerge，用于标记哪些属性需要合并，哪个是主键

/**
 * 自定义注解，用于判断是否需要合并以及合并的主键
 * 标记哪些属性需要合并，哪个是主键
 */
@Target({ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
public @interface CollectCustomMerge {

    /**
     * 是否需要合并单元格
     */
    boolean needMerge() default false;

    /**
     * 是否是主键,即该字段相同的行合并
     */
    boolean isPk() default false;
}

创建自定义单元格合并策略类CustomMergeStrategy，当Excel中两列主键相同时，合并被标记需要合并的列

import com.alibaba.excel.annotation.ExcelProperty;
import com.alibaba.excel.write.handler.RowWriteHandler;
import com.alibaba.excel.write.metadata.holder.WriteSheetHolder;
import com.alibaba.excel.write.metadata.holder.WriteTableHolder;
import com.easyexcle.demo.easyExcel.annotion.CollectCustomMerge;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.util.CellRangeAddress;

import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.List;

/**
 * @Author: lkz
 * @Title: CustomMergeStrategy
 * @Description: 自定义单元格合并策略类CustomMergeStrategy，当Excel中两列主键相同时，合并被标记需要合并的列
 * @Date: 2023/7/5 9:16
 */
public class CustomMergeStrategy implements RowWriteHandler {
    /**
     * 主键下标
     */
    private Integer pkIndex;

    /**
     * 需要合并的列的下标集合
     */
    private List<Integer> needMergeColumnIndex = new ArrayList<>();

    /**
     * DTO数据类型
     */
    private Class<?> elementType;

    public CustomMergeStrategy(Class<?> elementType) {
        this.elementType = elementType;
    }

    @Override
    public void beforeRowCreate(WriteSheetHolder writeSheetHolder, WriteTableHolder writeTableHolder, Integer rowIndex, Integer relativeRowIndex, Boolean isHead) {

    }

    @Override
    public void afterRowCreate(WriteSheetHolder writeSheetHolder, WriteTableHolder writeTableHolder, Row row, Integer relativeRowIndex, Boolean isHead) {

    }

    @Override
    public void afterRowDispose(WriteSheetHolder writeSheetHolder, WriteTableHolder writeTableHolder, Row row, Integer relativeRowIndex, Boolean isHead) {
        // 如果是标题,则直接返回
        if (isHead) {
            return;
        }

        // 获取当前sheet
        Sheet sheet = writeSheetHolder.getSheet();

        // 获取标题行
        Row titleRow = sheet.getRow(0);

        if (null == pkIndex) {
            this.lazyInit(writeSheetHolder);
        }

        // 判断是否需要和上一行进行合并
        // 不能和标题合并，只能数据行之间合并
        if (row.getRowNum() <= 1) {
            return;
        }
        // 获取上一行数据
        Row lastRow = sheet.getRow(row.getRowNum() - 1);
        // 将本行和上一行是同一类型的数据(通过主键字段进行判断)，则需要合并
        if (lastRow.getCell(pkIndex).getStringCellValue().equalsIgnoreCase(row.getCell(pkIndex).getStringCellValue())) {
            for (Integer needMerIndex : needMergeColumnIndex) {
                CellRangeAddress cellRangeAddress = new CellRangeAddress(row.getRowNum() - 1, row.getRowNum(),
                        needMerIndex, needMerIndex);
                sheet.addMergedRegionUnsafe(cellRangeAddress);
            }
        }
    }

    /**
     * 初始化主键下标和需要合并字段的下标
     */
    private void lazyInit(WriteSheetHolder writeSheetHolder) {

        // 获取当前sheet
        Sheet sheet = writeSheetHolder.getSheet();

        // 获取标题行
        Row titleRow = sheet.getRow(0);
        // 获取DTO的类型
        Class<?> eleType = this.elementType;

        // 获取DTO所有的属性
        Field[] fields = eleType.getDeclaredFields();

        // 遍历所有的字段，因为是基于DTO的字段来构建excel，所以字段数 >= excel的列数
        for (Field theField : fields) {
            // 获取@ExcelProperty注解，用于获取该字段对应在excel中的列的下标
            ExcelProperty easyExcelAnno = theField.getAnnotation(ExcelProperty.class);
            // 为空,则表示该字段不需要导入到excel,直接处理下一个字段
            if (null == easyExcelAnno) {
                continue;
            }
            // 获取自定义的注解，用于合并单元格
            CollectCustomMerge collectCustomMerge = theField.getAnnotation(CollectCustomMerge.class);

            // 没有@CustomMerge注解的默认不合并
            if (null == collectCustomMerge) {
                continue;
            }

            for (int index = 0; index < fields.length; index++) {
                Cell theCell = titleRow.getCell(index);
                // 当配置为不需要导出时，返回的为null，这里作一下判断，防止NPE
                if (null == theCell) {
                    continue;
                }
                // 将字段和excel的表头匹配上
                if (easyExcelAnno.value()[0].equalsIgnoreCase(theCell.getStringCellValue())) {
                    if (collectCustomMerge.isPk()) {
                        pkIndex = index;
                    }

                    if (collectCustomMerge.needMerge()) {
                        needMergeColumnIndex.add(index);
                    }
                }
            }
        }

        // 没有指定主键，则异常
        if (null == this.pkIndex) {
            throw new IllegalStateException("使用@CustomMerge注解必须指定主键");
        }

    }
}

测试最终效果

public class CollectTest {


    public static void main(String[] args) {
    
        List<OrderData> orderDataList=new ArrayList<>();
        orderDataList.add(new OrderData("1",new Date(),"南京","001","商品名称1","标题1"));
        orderDataList.add(new OrderData("1",new Date(),"南京","001","商品名称2","标题2"));
        orderDataList.add(new OrderData("2",new Date(),"北京","002","商品名称02","标题02"));
        orderDataList.add(new OrderData("2",new Date(),"北京","003","商品名称03","标题1"));
        orderDataList.add(new OrderData("1",new Date(),"南京","001","商品名称3","标题3"));
        orderDataList.add(new OrderData("3",new Date(),"上海","001","商品名称3","标题3"));
        orderDataList.add(new OrderData("3",new Date(),"天津","001","商品名称302","标题302"));
        orderDataList.add(new OrderData("3",new Date(),"上海","001","商品名称303","标题303"));
        orderDataList.add(new OrderData("4",new Date(),"杭州","001","商品名称4","标题4"));
        orderDataList.add(new OrderData("5",new Date(),"杭州","001","商品名称5","标题5"));


        EasyExcel.write("D:/pdf/CollectExport.xlsx").head(OrderData.class)
                .registerWriteHandler(new CustomMergeStrategy(OrderData.class))
                .sheet().doWrite(orderDataList);

    }

}

注意事项

效果