下载数据库内容到EXCEL文件

@GetMapping("/downloadExcel")
public void downloadExcel(HttpServletResponse response) {
    response.setContentType("application/force-download");// 设置强制下载不打开
    File excel;
    try {
        excel = this.backUpService.getBackUpExcel();
    } catch (IOException e) {
       // log.error(e.toString());
        e.printStackTrace();
        return;
    }
    response.addHeader("Content-Disposition", "attachment;fileName=" + excel.getName());// 设置文件名
    wirteFile(excel,response);
}

    @Override
    public File getBackUpExcel() throws IOException {
        List<Candidate> candidateList = this.candidateMapper.listCandidate(null,null,null,0,0);
        List<ExamCourse> examCourseList = this.examCourseMapper.listExamCourse(null,null,null,null,null,0,0);
        Map<Long,ExamCourse> examCourse = new HashMap<>();
        Iterator var4 = examCourseList.iterator();
        while (var4.hasNext()){
            ExamCourse e = (ExamCourse) var4.next();
            examCourse.put(e.getId(),e);
        }
        Calendar calendar = Calendar.getInstance();
        File file = new File(getExcelPath(calendar))

        if(file.exists()&&file.isFile()&&!file.delete()){
            throw new RuntimeException("删除原文件出错");
        } else if(!file.createNewFile()){
            throw new RuntimeException("新建文件出错");
        }else {
            PrintWriter printWriter;
            try {
                // printWriter = new PrintWriter(file,"gb2312");
                printWriter = new PrintWriter(file, "GBK");
            } catch (FileNotFoundException e) {
                e.printStackTrace();
                throw new RuntimeException("新建文件未找到");
            }
            printWriter.write("序号,姓名,身份证号码,科目名称,性别,准考证号,微信,电话,联系E-mail,考点,考试日期,开考时间,考试时长（分）,上下半年\r\n");
            int p = 1;
            for (Candidate candidate : candidateList) {
                candidate.setExamCourse(examCourse.get(candidate.getExamCourse().getId()));
                Calendar examTime = Calendar.getInstance();
                examTime.setTime(candidate.getExamCourse().getExamTime());
                printWriter.write(p++ + "," + candidate.getName() + ","
                        + ((char) (9)) + candidate.getIdNumber() + ","
                        + candidate.getExamCourse().getCourse().getCourseName() + ","
                        + (candidate.getSex() ? "女" : "男") + "," + candidate.getExamineeNumber() + ","
                        + (candidate.getWechat() == null ? "" : candidate.getWechat()) + ","
                        + ((char) (9)) + candidate.getPhoneNumber() + ","
                        + candidate.getEmail() + ","
                        + candidate.getExamCourse().getExamLocation().getExamLocationName() + ","
                        + examTime.get(Calendar.YEAR) + "-"
                        + (examTime.get(Calendar.MONTH) + 1) + "-"
                        + examTime.get(Calendar.DATE) + ","
                        + examTime.get(Calendar.HOUR) + ":" + examTime.get(Calendar.MINUTE) + ","
                        + candidate.getExamCourse().getExamTimeLength() + ","
                        + (candidate.getExamCourse().getTerm() ? "下" : "上") + "\r\n");
            }
            printWriter.flush();
            printWriter.close();
            return file;
        }
    }

private String getExcelPath(Calendar calendar) {
        String url = fileSaveConfigProperties.getPath() + "/excel";
        File file = new File(url);
        if(!file.exists()) {
            if(!file.mkdir())
                throw new RuntimeException("文件夹创建失败");
        }
　　　　//通过url创建文件夹中的.csv文件，以便往里面写入数据
        return url + "/" + calendar.get(Calendar.YEAR) +
                "_" + (calendar.get(Calendar.MONTH) + 1) +
                "_" + calendar.get(Calendar.DATE) +
                "." + "csv";
    }
}

@Configuration
@PropertySource("classpath:config/file_save.properties")
@Component
public class FileSaveConfigProperties {
//savePath在config下的properties文件中设置
    @Value("${savePath}")
    private String path;

    @Value("${delayed}")
    private int delayed;

    @Value("${Access-Control-Allow-Origin}")
    private String accessControlAllowOrigin;

}

    private static void wirteFile(File file, HttpServletResponse response) {
        byte[] buffer = new byte[2048];
        try(FileInputStream fis = new FileInputStream(file);
            BufferedInputStream bis = new BufferedInputStream(fis)) {
            OutputStream os = response.getOutputStream();
            int i = bis.read(buffer);
            while (i != -1) {
                os.write(buffer, 0, i);
                i = bis.read(buffer);
            }
            log.info("{} 文件输出完成",file.getName());
        } catch (Exception e) {
            log.error("{} 文件输出异常", file.getName());
        }
    }
}