Java完成POI的功能

　　POM文件　　　　　        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!--mysql驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi</artifactId>
            <version>3.17</version>
        </dependency>
        <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi-ooxml</artifactId>
            <version>3.17</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>tk.mybatis</groupId>
            <artifactId>mapper-spring-boot-starter</artifactId>
            <version>1.2.3</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.47</version>
        </dependency>
        <dependency>
            <groupId>net.sourceforge.nekohtml</groupId>
            <artifactId>nekohtml</artifactId>
            <version>1.9.15</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>

实体bean

@Data
@AllArgsConstructor
@NoArgsConstructor
public class TRole {
    private Integer id;

    private String name;

    private Integer age;
}

/**
*Excel工具类
*/
public class ExcelUtil {

    public static final String FILE_NAME = "用户表";

    public static final String EXCEL_XLS = "xls";
    public static final String EXCEL_XLSX = "xlsx";

    public static boolean isExcelXls(String filePath) {
        return filePath.matches("^.+\\.(?i)(xls)$");
    }

    public static boolean isExcelXlsx(String filePath) {

        return filePath.matches("^.+\\.(?i)(xlsx)$");
    }

    /**
     * 有些单元格为Numeric格式，带有指数E。因此，若想获取其String类型时，需要进行格式转换。
     *
     * @param cell
     * @return
     */
    public static String getStringFromNumericCell(Cell cell) {
        return new DecimalFormat("#").format(cell.getNumericCellValue());
    }

    /**
     * 通过WorkBook对象和sheet对象生成title
     *
     * @param wb    WorkBook对象
     * @param sheet sheet对象
     */
    public static void createTitle(Workbook wb, Sheet sheet) {
        //生成表的标题行
        Row row = sheet.createRow(0);
        //设置列宽
        sheet.setColumnWidth(1, 12 * 256);
        sheet.setColumnWidth(3, 17 * 256);
        //设置风格：字体加粗，居中
        CellStyle cellStyle = wb.createCellStyle();
        cellStyle.setAlignment(HorizontalAlignment.CENTER);
        Font font = wb.createFont();
        font.setBold(true);
        cellStyle.setFont(font);
        //根据对象属性设置单元格标题
        Cell cell0 = row.createCell(0);
        cell0.setCellValue("ID");
        cell0.setCellStyle(cellStyle);
        Cell cell1 = row.createCell(1);
        cell1.setCellValue("name");
        cell1.setCellStyle(cellStyle);
        Cell cell2 = row.createCell(2);
        cell2.setCellValue("age");
        cell2.setCellStyle(cellStyle);
    }

    /**
     * 生成文件在本地
     * @param fileName
     * @param wb
     */
    public static void buildExcelFile(String fileName, Workbook wb) {
        try {
            FileOutputStream fos = new FileOutputStream(fileName);
            wb.write(fos);
            fos.flush();
            fos.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    /**
     * 返回给浏览器
     * @param fileName
     * @param wb
     * @param response
     */
    public static void buildExcelFile(String fileName, Workbook wb, HttpServletResponse response) {
        try {
            response.setContentType("application/vnd.ms-excel");
            response.setHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(fileName, "utf-8"));
            ServletOutputStream outputStream = response.getOutputStream();
            wb.write(outputStream);
            outputStream.flush();
            outputStream.close();
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

/***Controller层操作，省略service和dao*/

@Controller@RequestMapping("/excel")public class ExcelController {

    @Autowired    ExcelService excelService;

    @RequestMapping("/")    public String toIndex() {        return "excel";    }

    @ResponseBody    @RequestMapping("/download/{way}")    public String excelFileDownload(@PathVariable String way, HttpServletResponse response) throws IOException {        Workbook wb = null;        String filename = ExcelUtil.FILE_NAME;        if (ExcelUtil.EXCEL_XLS.equals(way)) {            wb = new HSSFWorkbook();            filename += ".xls";        } else if ((ExcelUtil.EXCEL_XLSX.equals(way))) {            wb = new XSSFWorkbook();            filename += ".xlsx";        }        Sheet sheet = wb.createSheet("角色表");        ExcelUtil.createTitle(wb, sheet);

        //从数据库查出数据        List<TRole> tRoles = excelService.getAllRoles();        //记录新增行数据        int rowNum = 1;        for (TRole tRole : tRoles) {            Row row = sheet.createRow(rowNum);            row.createCell(0).setCellValue(tRole.getId());            row.createCell(1).setCellValue(tRole.getName());            row.createCell(2).setCellValue(tRole.getAge());            rowNum++;        }        //生成excel文件(在当前文件夹下)        //ExcelUtil.buildExcelFile(filename, wb);        //浏览器下载excel        ExcelUtil.buildExcelFile(filename, wb, response);        wb.close();        return "File downloaded successfully";

    }

    @ResponseBody    @RequestMapping("/upload")    public String excelFileUpload(MultipartFile file) throws IOException {        Workbook wb = null;        List<TRole> tRoleList = new ArrayList<>();        if (!ExcelUtil.isExcelXlsx(file.getOriginalFilename()) && !ExcelUtil.isExcelXls(file.getOriginalFilename())) {

            return "The file must be of excel type";        }        if (file.getOriginalFilename() == null || file.getOriginalFilename().equals("") || file.getSize() == 0) {            return "The file cannot be empty";        }        try {            if (ExcelUtil.isExcelXlsx(file.getOriginalFilename())) {                wb = new XSSFWorkbook(file.getInputStream());            } else {                wb = new HSSFWorkbook(file.getInputStream());            }            //获取第一张表(默认就设置成1张表吧)            Sheet sheet = wb.getSheetAt(0);            //获取行数            int rowsNum = sheet.getPhysicalNumberOfRows();            //遍历行            for (int i = 0; i < rowsNum; i++) {                //标题行省略                if (i == 0) {                    continue;                }                Row row = sheet.getRow(i);                //遍历每行的单元格//                for (int j=0;j<row.getPhysicalNumberOfCells();j++){//                    Cell cell = row.getCell(j);//                }                //这里我们直接操作具体的单元格                Integer id = Integer.valueOf(Double.valueOf(row.getCell(0).getNumericCellValue()).intValue());                String name = row.getCell(1).getStringCellValue();                Integer age = Integer.valueOf(Double.valueOf(row.getCell(2).getNumericCellValue()).intValue());                TRole tRole = new TRole(id, name, age);                tRoleList.add(tRole);            }

        } catch (IOException e) {            e.printStackTrace();        } finally {            wb.close();        }        return JSON.toJSONString(tRoleList);    }}

原文地址：https://www.cnblogs.com/hucheng1997/p/11426086.html