Java使用POI将数据库中查到的数据导入到excel中（新手篇）

最近在工作中遇到一个需求，将页面上的数据导出/下载到excel，百度了几篇文章，照着写出来了，感觉不是很“平易近人”，于是自己总结一篇，方便大家参考。

工具：Intellij IDEA、Navicat、Postman

我创建的是maven项目，所以jar在pom文件中引入，如下

        
            org.apache.poi
            poi
            3.17
        
        
            org.apache.poi
            poi-scratchpad
            3.17
        
        
            org.apache.poi
            poi-ooxml
            3.17
        
        
            org.apache.poi
            poi-ooxml-schemas
            3.17
        

 第一步，创建导出工具类，部分代码添加注释(其实也是在网上抄的自己改了一下哈哈哈哈哈)

package com.yuanmou.utils.poi;

import org.apache.poi.hssf.util.HSSFColor;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.ss.util.CellRangeAddress;
import org.apache.poi.xssf.usermodel.XSSFFont;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;

/**
 * @author Lebron
 * @ClassName ZxExportExcel
 * @Description TODO
 * @Date 2019/8/27 15:04
 * @Version 1.0
 */
public class ZxExportExcel {

    /**
     * 生成Excel
     */
    public XSSFWorkbook getWorkBook() {
        XSSFWorkbook wb = new XSSFWorkbook();
        Sheet sheet = wb.createSheet("0");
        for (int i = 0; i < 9; i++) {
            sheet.setColumnWidth(i, 4300);
        }

        /**
         * 单元格 样式
         */
        CellStyle cellStyle = wb.createCellStyle();
        cellStyle.setBorderTop(BorderStyle.THIN);
        cellStyle.setBorderBottom(BorderStyle.THIN);
        cellStyle.setBorderLeft(BorderStyle.THIN);
        cellStyle.setBorderRight(BorderStyle.THIN);
        cellStyle.setTopBorderColor(HSSFColor.BLACK.index);
        cellStyle.setBottomBorderColor(HSSFColor.BLACK.index);
        cellStyle.setLeftBorderColor(HSSFColor.BLACK.index);
        cellStyle.setRightBorderColor(HSSFColor.BLACK.index);
        cellStyle.setAlignment(HorizontalAlignment.CENTER); // 水平居中
        cellStyle.setVerticalAlignment(VerticalAlignment.CENTER); // 上下居中
        cellStyle.setFillForegroundColor(IndexedColors.AQUA.getIndex());
        cellStyle.setFillPattern(FillPatternType.SOLID_FOREGROUND);


        /**
         * 标题样式 样式
         */
        XSSFFont titleFont = wb.createFont();
        titleFont.setFontHeight(24);
        titleFont.setBold(true);
        CellStyle titleCellStyle = wb.createCellStyle();
        titleCellStyle.setBorderTop(BorderStyle.THIN);
        titleCellStyle.setBorderBottom(BorderStyle.THIN);
        titleCellStyle.setBorderLeft(BorderStyle.THIN);
        titleCellStyle.setBorderRight(BorderStyle.THIN);
        titleCellStyle.setTopBorderColor(HSSFColor.BLACK.index);
        titleCellStyle.setBottomBorderColor(HSSFColor.BLACK.index);
        titleCellStyle.setLeftBorderColor(HSSFColor.BLACK.index);
        titleCellStyle.setRightBorderColor(HSSFColor.BLACK.index);
        titleCellStyle.setAlignment(HorizontalAlignment.CENTER); // 水平居中
        titleCellStyle.setVerticalAlignment(VerticalAlignment.CENTER); // 上下居中
        titleCellStyle.setFont(titleFont);
        titleCellStyle.setFillForegroundColor(IndexedColors.GREY_50_PERCENT.getIndex());
        titleCellStyle.setFillPattern(FillPatternType.SOLID_FOREGROUND);

        /**
         * 主标题 在这里插入主标题
         */
        Row titleRow;
        Cell titleCell;
        sheet.addMergedRegion(new CellRangeAddress((short) 0, (short) 2, (short) 0, (short) 8));
        for (int i = 0; i <= 2; i++) {
            titleRow = sheet.createRow(i);
            for (int j = 0; j < 9; j++) {
                titleCell = titleRow.createCell(j);
                titleCell.setCellType(CellType.STRING);
                titleCell.setCellStyle(titleCellStyle);
                titleCell.setCellValue("测试导出标题");
            }
        }

        /**
         * 列标题 在这里插入标题
         */
        Row rowLabel;
        Cell cellLabel;
        rowLabel = sheet.createRow(3);
        cellLabel = rowLabel.createCell(0);
        cellLabel.setCellType(CellType.STRING);
        cellLabel.setCellStyle(cellStyle);
        cellLabel.setCellValue("设备编号");
        cellLabel = rowLabel.createCell(1);
        cellLabel.setCellType(CellType.STRING);
        cellLabel.setCellStyle(cellStyle);
        cellLabel.setCellValue("规格型号");
        cellLabel = rowLabel.createCell(2);
        cellLabel.setCellType(CellType.STRING);
        cellLabel.setCellStyle(cellStyle);
        cellLabel.setCellValue("设备类型");
        cellLabel = rowLabel.createCell(3);
        cellLabel.setCellType(CellType.STRING);
        cellLabel.setCellStyle(cellStyle);
        cellLabel.setCellValue("登记日期");
        cellLabel = rowLabel.createCell(4);
        cellLabel.setCellType(CellType.STRING);
        cellLabel.setCellStyle(cellStyle);
        cellLabel.setCellValue("安装地点");
        cellLabel = rowLabel.createCell(5);
        cellLabel.setCellType(CellType.STRING);
        cellLabel.setCellStyle(cellStyle);
        cellLabel.setCellValue("安装坐标");
        cellLabel = rowLabel.createCell(6);
        cellLabel.setCellType(CellType.STRING);
        cellLabel.setCellStyle(cellStyle);
        cellLabel.setCellValue("误差范围/米");
        cellLabel = rowLabel.createCell(7);
        cellLabel.setCellType(CellType.STRING);
        cellLabel.setCellStyle(cellStyle);
        cellLabel.setCellValue("片区");
        cellLabel = rowLabel.createCell(8);
        cellLabel.setCellType(CellType.STRING);
        cellLabel.setCellStyle(cellStyle);
        cellLabel.setCellValue("提交人");
        /**
         * 页脚
         */
        setExcelFooterName("测试-页脚", 0, wb);
        return wb;
    }

    /**
     * 设置Excel页脚
     */
    public void setExcelFooterName(String customExcelFooterName, int setExcelFooterNumber, XSSFWorkbook wb) {
        wb.setSheetName(setExcelFooterNumber, customExcelFooterName);
    }

    /**
     * 输出流 导出Excel到桌面
     */
    public void exportOutPutExcel(String exportPositionPath, XSSFWorkbook wb) {
        try {
            File file = new File(exportPositionPath);
            FileOutputStream fileOutputStream = new FileOutputStream(file);
            wb.write(fileOutputStream);
            fileOutputStream.close();
        } catch (IOException e) {
            System.err.println(e.getMessage());
        }
    }
}

mapper接口：因为是测试，所以随便查了一张表

List selectAll();

mapper.xml：大家根据需求贴上自己的sql即可

    SELECT
    fr.*,a.area_name aName,u.user_name uName
    FROM sys_facility_register fr
    INNER JOIN sys_area a ON fr.a_id = a.id
    INNER JOIN sys_user u ON fr.u_id = u.id
  

下面是查到的数据，因为是测试用的数据库，所以数据很乱。

service接口：

List selectAll();

serviceimpl实现service：

@Override
    public List selectAll() {
        return sysFacilityResisterMapper.selectAll();
    }

感觉自己属实有点啰嗦......不过还是希望给小白带来帮助，毕竟大家都是从小白一路走来的。

接着是controller：

/**
     * @param
     * @return
     * @Author Lebron
     * @Date 2019/8/28 15:32
     * @Description 测试下载/导出 TODO
     */
    @GetMapping("/export")
    public void export() {
        ZxExportExcel zxExportExcel = new ZxExportExcel();
        XSSFWorkbook wb = zxExportExcel.getWorkBook();
        Sheet sheet = wb.getSheetAt(0);
        CellStyle cellStyle = wb.createCellStyle();
        cellStyle.setBorderTop(BorderStyle.THIN);
        cellStyle.setBorderBottom(BorderStyle.THIN);
        cellStyle.setBorderLeft(BorderStyle.THIN);
        cellStyle.setBorderRight(BorderStyle.THIN);
        cellStyle.setTopBorderColor(HSSFColor.BLACK.index);
        cellStyle.setBottomBorderColor(HSSFColor.BLACK.index);
        cellStyle.setLeftBorderColor(HSSFColor.BLACK.index);
        cellStyle.setRightBorderColor(HSSFColor.BLACK.index);
        cellStyle.setAlignment(HorizontalAlignment.CENTER); // 水平居中
        cellStyle.setVerticalAlignment(VerticalAlignment.CENTER); // 上下居中

        Cell cellCheck;
        List facilityResisters = sysFacilityResisterService.selectAll();
        for (int i = 0; i < facilityResisters.size(); i++) {
            SysFacilityResisterParam facilityResister = facilityResisters.get(i);
            String facilityCode = facilityResister.getFacilityCode();
            String item = facilityResister.getItem();
            String facilityType = facilityResister.getFacilityType();
            Date createTime = facilityResister.getStartTime();
            String sysDate = TimeUtil.getSysDate(createTime);
            String installSite = facilityResister.getInstallSite();
            String installCoordinate = facilityResister.getInstallCoordinate();
            String coordinate = facilityResister.getCoordinate();
            String aName = facilityResister.getAName();
            String uName = facilityResister.getUName();
            Row rowCheck = sheet.createRow(4 + i);
            cellCheck = rowCheck.createCell(0);
            cellCheck.setCellType(CellType.STRING);
            cellCheck.setCellStyle(cellStyle);
            cellCheck.setCellValue(facilityCode);
            cellCheck = rowCheck.createCell(1);
            cellCheck.setCellType(CellType.STRING);
            cellCheck.setCellStyle(cellStyle);
            cellCheck.setCellValue(item);
            cellCheck = rowCheck.createCell(2);
            cellCheck.setCellType(CellType.STRING);
            cellCheck.setCellStyle(cellStyle);
            cellCheck.setCellValue(facilityType);
            cellCheck = rowCheck.createCell(3);
            cellCheck.setCellType(CellType.STRING);
            cellCheck.setCellStyle(cellStyle);
            cellCheck.setCellValue(sysDate);
            cellCheck = rowCheck.createCell(4);
            cellCheck.setCellType(CellType.STRING);
            cellCheck.setCellStyle(cellStyle);
            cellCheck.setCellValue(installSite);
            cellCheck = rowCheck.createCell(5);
            cellCheck.setCellType(CellType.STRING);
            cellCheck.setCellStyle(cellStyle);
            cellCheck.setCellValue(installCoordinate);
            cellCheck = rowCheck.createCell(6);
            cellCheck.setCellType(CellType.STRING);
            cellCheck.setCellStyle(cellStyle);
            cellCheck.setCellValue(coordinate);
            cellCheck = rowCheck.createCell(7);
            cellCheck.setCellType(CellType.STRING);
            cellCheck.setCellStyle(cellStyle);
            cellCheck.setCellValue(aName);
            cellCheck = rowCheck.createCell(8);
            cellCheck.setCellType(CellType.STRING);
            cellCheck.setCellStyle(cellStyle);
            cellCheck.setCellValue(uName);
        }
        zxExportExcel.exportOutPutExcel("C:\\\\xinao\\\\poi\\\\download\\\\测试.xlsx", wb);
    }

因为平时开发都是使用Postman调试接口，所以就写了一个controller，如果你正巧没有使用过此工具可以百度一下使用方法，毕竟这个工具也是程序猿必备，我建议你了解一下。或者自己写个main函数测试一下，这里我就不贴代码了，相信聪明的你一定OK！

最后就是调接口测试辣！接口地址：http://localhost:8080/xinao/api/sys/facilityresister/export

 

 下面是我下载出的内容，虽然很丑但是凑合看吧，测试也懒得去优化，代码也写得很乱，大家在用的时候不要嫌弃。

 好啦，关于导出/下载到这儿就结束了，我觉着只要大家有耐心就一定没问题的，作为程序员，轻易放弃可不是什么好习惯，有问题可以在评论处留言，方便大家共同讨论！

突然想起我还用了一个时间工具类，下面也把代码贴出来，就是简单的转化格式。时间格式根据你存储的格式而定，如果你没有加时分秒下面的工具类也去掉即可。

public class TimeUtil {
    public static String getSysDate(Date date) {
        SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        String time = formatter.format(date);
        return time;
    }
}