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easyexcel将对象处理为多列，自增序列
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概述
主要記錄在開發中遇到的問題：使用easyexcel導出excel，一般數據都是保存在數據庫中，如果查詢返回的是一個實體類，且里面有嵌套的實體類對象，這時導出的時候要先對查詢出的數據進行業務邏輯處理，讓它符合導出規范，但是當數據量很大時，容易jvm內存，easyexcel(CellDataTypeEnum)只支持基本數據類型的導入，如圖1-1所示，可以通過自定義數據類型(Converter)進行轉換，但是這樣只能返回一種基本的數據類型，像這種實體類里面通常會有很多信息，如果都要導出，這種方式也不合適。目前我能想到的方式是通過它提供的各種攔截器處理，大概流程如下：
通過自定義數據類型將實體類轉換為String類型，然后通過攔截器將字符串拆分，添加對應列的數據。
圖1-1 excel內部支持的數據類型
代碼展示
import com.alibaba.excel.converters.Converter;
import com.alibaba.excel.converters.WriteConverterContext;
import com.alibaba.excel.enums.CellDataTypeEnum;
import com.alibaba.excel.metadata.data.WriteCellData;import java.text.SimpleDateFormat;
import java.util.Date;/*** @Description excel日期轉換類 即將Mongo中類型為long的時間戳轉化為yyyy-MM-dd HH:mm:ss時間* @author HuangAnting* @date 2022/4/8 10:16
*/
public class DateConverter implements Converter<Long> {@Overridepublic Class<?> supportJavaTypeKey() {//對象屬性類型return Long.class;}@Overridepublic CellDataTypeEnum supportExcelTypeKey() {//CellData屬性類型return CellDataTypeEnum.STRING;}@Overridepublic WriteCellData<?> convertToExcelData(WriteConverterContext<Long> context) throws Exception {//對象屬性轉CellDataLong cellValue = context.getValue();new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date(cellValue));if (cellValue == null) {return new WriteCellData<>("");} else {return new WriteCellData<>( new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date(cellValue)));}}
}
import com.alibaba.excel.write.handler.RowWriteHandler;
import com.alibaba.excel.write.metadata.holder.WriteSheetHolder;
import com.alibaba.excel.write.metadata.holder.WriteTableHolder;
import org.apache.poi.ss.usermodel.*;/*** @Description 自增序號攔截器* @author HuangAnting* @date 2022/4/12 17:27
*/
public class IndexRowWriteHandler implements RowWriteHandler {private static final String FIRST_CELL_NAME = "序號";/*** 序號的樣式，與其他列保持一樣的樣式*/private CellStyle firstCellStyle;private String description;/*** 列號*/private int count = 0;public IndexRowWriteHandler(String description){this.description = description;}@Overridepublic void afterRowDispose(WriteSheetHolder writeSheetHolder, WriteTableHolder writeTableHolder, Row row, Integer relativeRowIndex, Boolean isHead) {// 每一行首列單元格Cell indexCell = row.createCell(0);if(!isHead){indexCell.setCellValue(++count);try {row.getCell(3).setCellValue(description);}catch (Exception e){}}else {Workbook workbook = writeSheetHolder.getSheet().getWorkbook();firstCellStyle = firstCellStyle(workbook);indexCell.setCellValue(FIRST_CELL_NAME);indexCell.setCellStyle(firstCellStyle);writeSheetHolder.getSheet().setColumnWidth(0, 6 * 256);}}/*** excel首列序號列樣式* @param workbook* @return*/public CellStyle firstCellStyle(Workbook workbook) {CellStyle cellStyle = workbook.createCellStyle();//居中cellStyle.setAlignment(HorizontalAlignment.CENTER);cellStyle.setVerticalAlignment(VerticalAlignment.CENTER);cellStyle.setFillPattern(FillPatternType.SOLID_FOREGROUND);// 灰色cellStyle.setFillForegroundColor(IndexedColors.GREY_25_PERCENT.getIndex());//設置邊框cellStyle.setBorderBottom(BorderStyle.THIN);cellStyle.setBorderLeft(BorderStyle.THIN);cellStyle.setBorderRight(BorderStyle.THIN);cellStyle.setBorderTop(BorderStyle.THIN);//文字Font font = workbook.createFont();font.setBold(Boolean.TRUE);cellStyle.setFont(font);return cellStyle;}
}
import com.alibaba.excel.annotation.ExcelProperty;
import com.alibaba.excel.annotation.write.style.ColumnWidth;
import com.hat.easyexcel_export.excel.DateConverter;
import com.hat.easyexcel_export.excel.MonPointConverter;
import lombok.Data;/*** @Description 導出實體類* @author HuangAnting* @date 2022/4/12 17:26
*/
@Data
public class Car {/** 名稱*/@ExcelProperty(value = "名稱",index = 1)private String name;/** 價格*/@ExcelProperty(value = "價格",index = 2)private Double price;/** 描述*/@ColumnWidth(15)@ExcelProperty(value = "描述",index = 3)private String description;/** 坐標*/@ExcelProperty(value = "坐標",converter = MonPointConverter.class,index = 4)private MonPoint monPoint;/** 日期*/@ExcelProperty(value = "日期",converter = DateConverter.class)private Long createDate;
}
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.alibaba.fastjson.JSONObject;
import com.hat.easyexcel_export.entity.MonPoint;
import org.apache.poi.ss.usermodel.*;/*** @Description 行攔截器 將字符串的經緯度轉換成兩列數據* @author HuangAnting* @date 2022/4/12 17:26
*/
public class CustomRowWriteHandler implements RowWriteHandler {/*** 序號的樣式，與其他列保持一樣的樣式*/private CellStyle firstCellStyle;private static final String LON_CELL_NAME = "經度";private static final String LAT_CELL_NAME = "緯度";/*** 列號*/@Overridepublic void afterRowDispose(WriteSheetHolder writeSheetHolder, WriteTableHolder writeTableHolder, Row row, Integer integer, Boolean isHead) {Cell cell = row.getCell(4);row.removeCell(cell);Cell lon = row.createCell(4);Cell lat = row.createCell(5);if (!isHead) {String stringCellValue = cell.getStringCellValue();try {MonPoint monPoint = JSONObject.parseObject(stringCellValue, MonPoint.class);lon.setCellValue(monPoint.getLon());lat.setCellValue(monPoint.getLat());}catch (Exception e){}}else {Workbook workbook = writeSheetHolder.getSheet().getWorkbook();firstCellStyle = firstCellStyle(workbook);lon.setCellStyle(firstCellStyle);lat.setCellStyle(firstCellStyle);lon.setCellValue(LON_CELL_NAME);lat.setCellValue(LAT_CELL_NAME);}}/*** excel首列序號列樣式** @param workbook* @return*/public CellStyle firstCellStyle(Workbook workbook) {CellStyle cellStyle = workbook.createCellStyle();//居中cellStyle.setAlignment(HorizontalAlignment.CENTER);cellStyle.setVerticalAlignment(VerticalAlignment.CENTER);cellStyle.setFillPattern(FillPatternType.SOLID_FOREGROUND);// 灰色cellStyle.setFillForegroundColor(IndexedColors.GREY_25_PERCENT.getIndex());//設置邊框cellStyle.setBorderBottom(BorderStyle.THIN);cellStyle.setBorderLeft(BorderStyle.THIN);cellStyle.setBorderRight(BorderStyle.THIN);cellStyle.setBorderTop(BorderStyle.THIN);//文字Font font = workbook.createFont();font.setBold(Boolean.TRUE);cellStyle.setFont(font);return cellStyle;}
}
gitee地址：easyexcel_export
以上僅代表本人對easyexcel的認識和了解，歡迎大家批評指正。
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