spring boot定时任务接收邮件并且存储附件的方法讲解

public class TimerTaskServiceImpl implements TimerTaskService {
  @Autowired
  private ParseTxtServiceImpl parseTxtService;
  /**
   * 接收邮件 
   */
  @Override
  @Scheduled(cron="0 10 8 * * ?")
  public void timerTaskInfo(){
    //邮件配置信息
    String host=Constants.MAIL_HOST;
    String userName=Constants.MAIL_USER_NAME;
    String passWord=Constants.MAIL_PASS_WORD;
    //邮件配置类
    Properties properties=new Properties();
    //邮件配置缓存
    Session session=Session.getDefaultInstance(properties);
    session.setDebug(true);
    String fileName=null;
    try {
      //邮件服务器的类型
      Store store = session.getStore("pop3");
      //连接邮箱服务器
      store.connect(host,userName,passWord);
      // 获得用户的邮件帐户
      Folder folder=store.getFolder("INBOX");
      if (folder == null) {
        logger.info("获取邮箱文件信息为空");
      }
      // 设置对邮件帐户的访问权限可以读写
      folder.open(Folder.READ_WRITE);
      Calendar calendar=Calendar.getInstance();
      calendar.add(Calendar.DATE,-1);
      Date mondayDate = calendar.getTime();
      SearchTerm comparisonTermLe = new SentDateTerm(ComparisonTerm.GT, mondayDate);
      SearchTerm address=new SubjectTerm( "MU Report");
      SearchTerm comparisonAndTerm = new AndTerm(address, comparisonTermLe);
      Message[] messages = folder.search(comparisonAndTerm);
      for(int i = 0 ; i < messages.length ; i++){
        MimeMessage msg = (MimeMessage) messages[i];
        //判断是否有附件
        boolean isContainerAttachment = isContainAttachment(msg);
        if (isContainerAttachment) {
          //保存附件
          fileName=saveAttachment(msg,Constants.STORAGE_FILE);
          //保存接收到的邮件并且收件箱删除邮件
         msg.setFlag(Flags.Flag.DELETED, true);
        }
        if(!isContainerAttachment) {
          continue;
        }
      }
      folder.close(true);
      store.close();
      parseTxtService.readTxt(fileName);
    }catch (NoSuchProviderException e){
      loggerError.error("接收邮箱信息异常:{}",e);
    }catch (MessagingException e){
      loggerError.error("连接邮箱服务器信息异常:{}",e);
    }catch (IOException e){
      loggerError.error("接收邮箱信息解析异常:{}",e);
    }catch (IllegalStateException e){
      loggerError.error("接收邮箱信息为空:{}",e);
    }
  }
  /**
   * 判断邮件中是否包含附件
   * @return 邮件中存在附件返回true，不存在返回false
   * @throws MessagingException
   * @throws IOException
   */
  public static boolean isContainAttachment(Part part) throws MessagingException, IOException {
    boolean flag = false;
    if (part.isMimeType(Constants.MULTI_PART)) {
      MimeMultipart multipart = (MimeMultipart) part.getContent();
      int partCount = multipart.getCount();
      for (int i = 0; i < partCount; i++) {
        BodyPart bodyPart = multipart.getBodyPart(i);
        String disp = bodyPart.getDisposition();
        if (disp != null && (disp.equalsIgnoreCase(Part.ATTACHMENT) ||
            disp.equalsIgnoreCase(Part.INLINE))) {
          flag = true;
        } else if (bodyPart.isMimeType(Constants.MULTI_PART)) {
          flag = isContainAttachment(bodyPart);
        } else {
          String contentType = bodyPart.getContentType();
          if (contentType.indexOf(Constants.APPLICATION_CONTEXT) != -1) {
            flag = true;
          }
          if (contentType.indexOf(Constants.NAME_CONTEXT) != -1) {
            flag = true;
          }
        }
        if (flag){
          break;
        }
      }
    } else if (part.isMimeType(Constants.MESSAGE_RFC)) {
      flag = isContainAttachment((Part)part.getContent());
    }
    return flag;
  }
  /**
   * 保存附件
   * @param part 邮件中多个组合体中的其中一个组合体
   * @param destDir 附件保存目录
   * @throws UnsupportedEncodingException
   * @throws MessagingException
   * @throws FileNotFoundException
   * @throws IOException
   */
  public String saveAttachment(Part part, String destDir) throws UnsupportedEncodingException,
      MessagingException, FileNotFoundException, IOException {
    String fileName=null;
    if (part.isMimeType(Constants.MULTI_PART)) {
      Multipart multipart = (Multipart) part.getContent();  //复杂体邮件
      //复杂体邮件包含多个邮件体
      int partCount = multipart.getCount();
      for (int i = 0; i < partCount; i++) {
        //获得复杂体邮件中其中一个邮件体
        BodyPart bodyPart = multipart.getBodyPart(i);
        //某一个邮件体也有可能是由多个邮件体组成的复杂体
        String disp = bodyPart.getDisposition();
        if (disp != null && (disp.equalsIgnoreCase(Part.ATTACHMENT) || disp.equalsIgnoreCase
            (Part.INLINE))) {
          InputStream is = bodyPart.getInputStream();
          saveFile(is, destDir, decodeText(bodyPart.getFileName()));
          fileName=decodeText(bodyPart.getFileName());
        } else if (bodyPart.isMimeType(Constants.MULTI_PART)) {
          saveAttachment(bodyPart,destDir);
        } else {
          String contentType = bodyPart.getContentType();
          if (contentType.indexOf(Constants.NAME_CONTEXT) != -1 || contentType.indexOf
              (Constants.APPLICATION_CONTEXT) != -1) {
            saveFile(bodyPart.getInputStream(), destDir, decodeText(bodyPart.getFileName()));
            fileName=decodeText(bodyPart.getFileName());
          }
        }
      }
    } else if (part.isMimeType(Constants.MESSAGE_RFC)) {
      saveAttachment((Part) part.getContent(),destDir);
    }
    return fileName;
  }
  /**
   * 读取输入流中的数据保存至指定目录
   * @param is 输入流
   * @param fileName 文件名
   * @param destDir 文件存储目录
   * @throws FileNotFoundException
   * @throws IOException
   */
  private void saveFile(InputStream is, String destDir, String fileName)
      throws FileNotFoundException, IOException {
    BufferedInputStream bis = new BufferedInputStream(is);
    if(fileName.contains(Constants.TXT_SUFIXX)) {
      BufferedOutputStream bos = new BufferedOutputStream(
          new FileOutputStream(new File(destDir + fileName)));
      int len = -1;
      while ((len = bis.read()) != -1) {
        bos.write(len);
        bos.flush();
      }
      bos.close();
      bis.close();
    }
  }
}