FileManager/ruoyi-common/src/main/java/com/ruoyi/common/excel/CellMergeStrategy.java

package com.ruoyi.common.excel;

import com.alibaba.excel.metadata.Head;
import com.alibaba.excel.write.merge.AbstractMergeStrategy;
import com.ruoyi.common.annotation.CellMerge;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.SneakyThrows;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.collections4.CollectionUtils;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.util.CellRangeAddress;

import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * 列值重复合并策略
 *
 * @author Lion Li
 */
@AllArgsConstructor
@Slf4j
public class CellMergeStrategy extends AbstractMergeStrategy {

	private List<?> list;
	private boolean hasTitle;

	@Override
	protected void merge(Sheet sheet, Cell cell, Head head, Integer relativeRowIndex) {
		List<CellRangeAddress> cellList = handle(list, hasTitle);
		// judge the list is not null
		if (CollectionUtils.isNotEmpty(cellList)) {
			// the judge is necessary
			if (cell.getRowIndex() == 1 && cell.getColumnIndex() == 0) {
				for (CellRangeAddress item : cellList) {
					sheet.addMergedRegion(item);
				}
			}
		}
	}

	@SneakyThrows
	private static List<CellRangeAddress> handle(List<?> list, boolean hasTitle) {
		List<CellRangeAddress> cellList = new ArrayList<>();
		if (CollectionUtils.isEmpty(list)) {
			return cellList;
		}
		Class<?> clazz = list.get(0).getClass();
		Field[] fields = clazz.getDeclaredFields();
		// 有注解的字段
		List<Field> mergeFields = new ArrayList<>();
		List<Integer> mergeFieldsIndex = new ArrayList<>();
		for (int i = 0; i < fields.length; i++) {
			Field field = fields[i];
			if (field.isAnnotationPresent(CellMerge.class)) {
				CellMerge cm = field.getAnnotation(CellMerge.class);
				mergeFields.add(field);
				mergeFieldsIndex.add(cm.index() == -1 ? i : cm.index());
			}
		}
		// 行合并开始下标
		int rowIndex = hasTitle ? 1 : 0;
		Map<Field, RepeatCell> map = new HashMap<>();
		// 生成两两合并单元格
		for (int i = 0; i < list.size(); i++) {
			for (int j = 0; j < mergeFields.size(); j++) {
				Field field = mergeFields.get(j);
				String name = field.getName();
				String methodName = "get" + name.substring(0, 1).toUpperCase() + name.substring(1);
				Method readMethod = clazz.getMethod(methodName);
				Object val = readMethod.invoke(list.get(i));

				int colNum = mergeFieldsIndex.get(j);
				if (!map.containsKey(field)) {
					map.put(field, new RepeatCell(val, i));
				} else {
					RepeatCell repeatCell = map.get(field);
					Object cellValue = repeatCell.getValue();
					if (cellValue == null || "".equals(cellValue)) {
						// 空值跳过不合并
						continue;
					}
					if (!cellValue.equals(val)) {
						if (i - repeatCell.getCurrent() > 1) {
							cellList.add(new CellRangeAddress(repeatCell.getCurrent() + rowIndex, i + rowIndex - 1, colNum, colNum));
						}
						map.put(field, new RepeatCell(val, i));
					} else if (i == list.size() - 1) {
						if (i > repeatCell.getCurrent()) {
							cellList.add(new CellRangeAddress(repeatCell.getCurrent() + rowIndex, i + rowIndex, colNum, colNum));
						}
					}
				}
			}
		}
		return cellList;
	}

	@Data
	@AllArgsConstructor
	static class RepeatCell {

		private Object value;

		private int current;

	}
}