EasyExcel将数据库中的多张表数据写入文件的多个sheet

参考：https://www.jianshu.com/p/d1d264c817ef

项目地址：https://gitee.com/lierwang99/mvn-testng.git

头疼：自己一直没找到可以将数据追加写入到同一个文件办法，所以实现了多个sheet同时写入一个文件

写完的效果图：

pom.xml引入的easyexcel版本

		<!-- https://mvnrepository.com/artifact/com.alibaba/easyexcel -->
		<dependency>
			<groupId>com.alibaba</groupId>
			<artifactId>easyexcel</artifactId>
			<version>2.2.10</version>
		</dependency>

一次写入一个sheet

	@SuppressWarnings("rawtypes")
	public static <T> void writeOne(String fileName, List list, Class<T> t) {
		// 指定文件，自定义列宽，注册样式
		EasyExcel.write(fileName).registerWriteHandler(new CustomCellWriteHandler())
				.registerWriteHandler(createStyleStrategy())
				// 这里放入动态头，定义Sheet名称
				.head(t).sheet(t.getSimpleName())
				//要写入的数据
				.doWrite(list);
	}

 一次写入多个sheet

	@SuppressWarnings("rawtypes")
	public static void writeMore(String fileName, Map<Class, List> map) {
		// 指定文件，自定义列宽，注册样式
		ExcelWriter excelWriter = EasyExcel.write(fileName).registerWriteHandler(new CustomCellWriteHandler())
				.registerWriteHandler(createStyleStrategy()).build();
		int i = 0;
		for (Class c : map.keySet()) {
			WriteSheet writeSheet = EasyExcel.writerSheet(i++, c.getSimpleName()).head(c).build();
			excelWriter.write(map.get(c), writeSheet);
		}
        //这一步很关键，不然文件会损坏
		excelWriter.finish();
	}

自定义列宽类

package com.entity;

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

import org.apache.poi.ss.usermodel.Cell;

import com.alibaba.excel.enums.CellDataTypeEnum;
import com.alibaba.excel.metadata.CellData;
import com.alibaba.excel.metadata.Head;
import com.alibaba.excel.util.CollectionUtils;
import com.alibaba.excel.write.metadata.holder.WriteSheetHolder;
import com.alibaba.excel.write.style.column.AbstractColumnWidthStyleStrategy;

//为了使我们写入的列能够自定义宽度，而不是所有列等宽，我们增加一个CustomCellWriteHandler类来自适应列宽度。
public class CustomCellWriteHandler extends AbstractColumnWidthStyleStrategy {
	private Map<Integer, Map<Integer, Integer>> CACHE = new HashMap<>();

	@SuppressWarnings("rawtypes")
	@Override
	protected void setColumnWidth(WriteSheetHolder writeSheetHolder, List<CellData> cellDataList, Cell cell, Head head,
			Integer integer, Boolean isHead) {
		boolean needSetWidth = isHead || !CollectionUtils.isEmpty(cellDataList);
		if (needSetWidth) {
			Map<Integer, Integer> maxColumnWidthMap = CACHE.get(writeSheetHolder.getSheetNo());
			if (maxColumnWidthMap == null) {
				maxColumnWidthMap = new HashMap<Integer, Integer>();
				CACHE.put(writeSheetHolder.getSheetNo(), maxColumnWidthMap);
			}

			Integer columnWidth = this.dataLength(cellDataList, cell, isHead);
			if (columnWidth >= 0) {
				if (columnWidth > 255) {
					columnWidth = 255;
				}

				Integer maxColumnWidth = maxColumnWidthMap.get(cell.getColumnIndex());
				if (maxColumnWidth == null || columnWidth > maxColumnWidth) {
					maxColumnWidthMap.put(cell.getColumnIndex(), columnWidth);
					writeSheetHolder.getSheet().setColumnWidth(cell.getColumnIndex(), columnWidth * 256);
				}

			}
		}
	}

	@SuppressWarnings("rawtypes")
	private Integer dataLength(List<CellData> cellDataList, Cell cell, Boolean isHead) {
		if (isHead) {
			// 此处加5可以额外扩充列宽度
			return cell.getStringCellValue().getBytes().length + 5;
		} else {
			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;
				}
			}
		}
	}
}

自定义表头样式类

	private static HorizontalCellStyleStrategy createStyleStrategy() {
		// 头的策略
		WriteCellStyle headWriteCellStyle = new WriteCellStyle();
		// 背景设置为红色
		headWriteCellStyle.setFillForegroundColor(IndexedColors.LIGHT_CORNFLOWER_BLUE.getIndex());
		WriteFont headWriteFont = new WriteFont();
		headWriteFont.setFontHeightInPoints((short) 10);
		headWriteCellStyle.setWriteFont(headWriteFont);
		// 内容的策略
		WriteCellStyle contentWriteCellStyle = new WriteCellStyle();
		contentWriteCellStyle.setBorderBottom(BorderStyle.THIN); // 底边框
		contentWriteCellStyle.setBorderLeft(BorderStyle.THIN); // 左边框
		contentWriteCellStyle.setBorderRight(BorderStyle.THIN); // 右边框
		contentWriteCellStyle.setBorderTop(BorderStyle.THIN); // 顶边框
		WriteFont contentWriteFont = new WriteFont();
		// 字体大小
		contentWriteFont.setFontHeightInPoints((short) 10);
		contentWriteCellStyle.setWriteFont(contentWriteFont);
		// 这个策略是 头是头的样式 内容是内容的样式 其他的策略可以自己实现
		HorizontalCellStyleStrategy horizontalCellStyleStrategy = new HorizontalCellStyleStrategy(headWriteCellStyle,
				contentWriteCellStyle);
		return horizontalCellStyleStrategy;
	}