使用JavaMail实现监控邮箱重要邮件并获取附件保存

需求描述

系统需要监控阿里云企业邮箱的收件信息，发现Dev发送过来的邮件，且附件名称满足一定格式要求的，我们需要将附件保存下来，并自动上传管理系统。已到达邮件及时有效处理且降低人力成本的目的。

技术储备

在实现这个功能之前我们需要了解一下与邮件有关的协议，smtp、pop3和imap协议，(关于smtp，pop3以及imap协议可以点击链接了解)在这里我们选择的是imap协议。因为我们需要更新邮件的状态，如果我们系统处理过邮件，那么我们要将它设计为已读状态。防止重复处理。

实现代码

获取邮箱IMAPStore的链接

 private IMAPStore getConnect() {
        //代理配置
        Properties props = System.getProperties();
        if (enableProxy) {
            props.setProperty("proxySet", "true");
            //使用测试环境专有的邮件代理IP
            props.setProperty("ProxyHost", proxyIpEmail);
            //使用测试环境专有的邮件代理端口
            props.setProperty("ProxyPort", proxyPortEmail);
        }
        IMAPStore store = null;
        props.setProperty("mail.store.protocol", protocol);
        props.setProperty("mail.imap.host", imapHost);
        props.setProperty("mail.imap.port", imapPort);
        props.setProperty("mail.imap.auth.login.disable", "true");
        authentication = new PasswordAuthentication(username, password);
        int tryTimes = 0;
        do {
            try {
                session = Session.getInstance(props, this);
                // 2、通过session得到Store对象
                store = (IMAPStore) session.getStore("imap");
                // 3、连上邮件服务器
                store.connect(username, password);
            } catch (Exception e) {
                Logs.error("第{}次尝试连接失败:{}", tryTimes, e.getMessage());
            }
            tryTimes++;
            //尝试10就可以了
            if (tryTimes >= EmailServiceImpl.TRY_TIMES) {
                break;
            }
            try {
                Thread.sleep(15000);
            } catch (InterruptedException e) {
                //ignore this exception
            }
        } while (true);
        return store;
    }

参数配置参考

mail.store.protocol=imap
mail.imap.host=imap.mxhichina.com
mail.imap.port=143
email.username=********
email.password=******

2. 获取收件夹中的未读邮件

  @Override
    public boolean receiveEmail() throws Exception {
        /**
         * 1. 取得链接
         */
        IMAPStore imapStore = getConnect();
        if (null == imapStore) {
            Logs.error("获取邮箱imap连接失败。方法执行失败。退出当前方法！！！！！！！");
            return false;
        }
        Folder folder = imapStore.getFolder("INBOX");
        folder.open(Folder.READ_WRITE);
        Message[] messages = folder.getMessages(folder.getMessageCount() - folder.getUnreadMessageCount() + 1, folder.getMessageCount());
        Logs.info("未读邮件数量:　{}", messages.length);
        for (Message msg : messages) {
            try {
                //邮件发送日期超过两天 退出遍历方法
                if (outDays(msg)) {
                    Logs.info("邮件{}已过期，退出循环", msg.getSubject());
                    continue;
                }
                //不是最新邮件，跳过
                if (isNew(msg)) {
                    Logs.info("邮件不是新邮件，跳过");
                    continue;
                }
                //是否属于需要处理的邮件
                if (!needProcessEmail(msg)) {
                    Logs.info("邮件不需要处理，跳过");
                    continue;
                }
                /**
                 * 处理邮件信息
                 */
                processEmailData(msg);
            } catch (Exception e) {
                Logs.error(e.getMessage(), e);
            }
        }
        //关闭资源
        folder.close(true);
        imapStore.close();
        return false;
    }

 /**
     * @param
     * @param msg
     * @return boolean
     * @author FeianLing
     * @date 2019/8/20
     * @desc 检查当前邮件是否已超过1天, 接收时间大于1天以前 返回true
     */
    private boolean outDays(Message msg) throws MessagingException {
        Date date = DateUtils.offsetDate(new Date(), emailOutDays);
        Date receiveDate = msg.getReceivedDate();
        Logs.info("邮件接收时间：{}", DateUtils.formatYmdHms(receiveDate));
        return receiveDate.getTime() - date.getTime() < 0;
    }
 /**
     * @param
     * @param msg
     * @return boolean
     * @author FeianLing
     * @date 2019/8/20
     * @desc 判断邮件是否是新的邮件
     */
    private boolean isNew(Message msg) throws MessagingException {
        boolean isNewFlag = false;
        Flags flags = msg.getFlags();
        Flags.Flag[] flagsArr = flags.getSystemFlags();
        Logs.info("邮件状态：" + JSONObject.toJSONString(flagsArr));
        for (Flags.Flag flag : flagsArr) {
            if (flag == Flags.Flag.SEEN) {
                isNewFlag = true;
                Logs.info("当前邮件为未读状态！");
                break;
            }
        }
        return isNewFlag;
    }
     /**
     * @param
     * @param msg
     * @return boolean
     * @author FeianLing
     * @date 2019/8/20
     * @desc 检查邮件内容是否需要我们处理
     * 1. 检查发件人是否满足要求
     * 2. 检查是否包含附件
     * 3. 检查是否有满足条件的附件
     */
    private boolean needProcessEmail(Message msg) throws Exception {
        Logs.info("needProcessEmail  > 当前邮件的标题：{}", msg.getSubject());
        // 1. 检查发件人邮箱是否包含在我们监控的邮箱列表里面
        String from = getFrom(msg);
        if (!monitoringEmail.contains(from)) {
            Logs.info("当前邮件的发件人[{}]不是我们要监控的对象", from);
            return false;
        }
        if (!isContainAttach((Part) msg)) {
            Logs.info("发件人满足要求但是附件为空，不满足我们监控的需求！");
            return false;
        }
        Map<String, InputStream> fileMap = new HashMap<>();
        getFileInputStream(msg, fileMap);
        if (fileMap.isEmpty()) {
            Logs.info("尽管邮件中有附件但是邮件中的附件却无一个满足要求！");
            return false;
        }
        return true;
    }
     /**
     * @param
     * @param part
     * @return java.io.InputStream
     * @author FeianLing
     * @date 2019/8/20
     * @desc 获取文件输入流
     */
    private void getFileInputStream(Part part, Map<String, InputStream> inputStreamMap) throws Exception {
        String fileName;
        if (part.isMimeType("multipart/*")) {
            Multipart mp = (Multipart) part.getContent();
            for (int i = 0; i < mp.getCount(); i++) {
                BodyPart mPart = mp.getBodyPart(i);
                String disposition = mPart.getDisposition();
                if ((disposition != null)
                        && ((disposition.equals(Part.ATTACHMENT)) || (disposition
                        .equals(Part.INLINE)))) {
                    fileName = mPart.getFileName();
                    if (fileName.toLowerCase().indexOf("gb2312") != -1) {
                        fileName = MimeUtility.decodeText(fileName);
                    }
                    if (checkFileName(fileName)) {
                        inputStreamMap.put(fileName, mPart.getInputStream());
                    }
                } else if (mPart.isMimeType("multipart/*")) {
                    Logs.info("子邮件里面的附件");
                    getFileInputStream(mPart, inputStreamMap);
                } else {
                    fileName = mPart.getFileName();
                    if ((fileName != null)
                            && (fileName.toLowerCase().indexOf("GB2312") != -1)) {
                        fileName = MimeUtility.decodeText(fileName);
                        if (checkFileName(fileName)) {
                            inputStreamMap.put(fileName, mPart.getInputStream());
                        }
                    }
                }
            }
        } else if (part.isMimeType("message/rfc822")) {
            getFileInputStream((Part) part.getContent(), inputStreamMap);
        }
    }

    /**
     * @param
     * @param fileName
     * @return boolean
     * @author FeianLing
     * @date 2019/8/20
     * @desc 检查文件名称是否符合要求 FTK-88584316 FTK-申请号.pdf
     */
    private boolean checkFileName(String fileName) {
        return EmailServiceImpl.FILENAME_REGEX.matcher(fileName).find();
    }

    /**
     * @param
     * @param part
     * @return boolean
     * @author FeianLing
     * @date 2019/8/20
     * @desc 判断邮件是否包含附件，如果没有包含附件，返回false 反之返回true
     */
    private boolean isContainAttach(Part part) throws Exception {
        boolean attachFlag = false;
        // String contentType = part.getContentType();
        if (part.isMimeType("multipart/*")) {
            Multipart mp = (Multipart) part.getContent();
            for (int i = 0; i < mp.getCount(); i++) {
                BodyPart mPart = mp.getBodyPart(i);
                String disposition = mPart.getDisposition();
                if ((disposition != null)
                        && ((disposition.equals(Part.ATTACHMENT)) || (disposition
                        .equals(Part.INLINE)))) {
                    attachFlag = true;
                } else if (mPart.isMimeType("multipart/*")) {
                    attachFlag = isContainAttach((Part) mPart);
                } else {
                    String conType = mPart.getContentType();

                    if (conType.toLowerCase().indexOf("application") != -1) {
                        attachFlag = true;
                    }
                    if (conType.toLowerCase().indexOf("name") != -1) {
                        attachFlag = true;
                    }
                }
            }
        } else if (part.isMimeType("message/rfc822")) {
            attachFlag = isContainAttach((Part) part.getContent());
        }
        return attachFlag;
    }

    /**
     * @param
     * @param msg
     * @return java.lang.String
     * @author FeianLing
     * @date 2019/8/20
     * @desc 获取发送地址
     */
    private String getFrom(Message msg) throws MessagingException {
        String from = "";
        InternetAddress[] addresses = (InternetAddress[]) msg.getFrom();
        if (null == addresses || addresses.length == 0) {
            Logs.error("无法获取发送人地址信息！");
            return from;
        }
        Address address = addresses[0];
        Logs.info("发件人地址json：" + JSONObject.toJSONString(address));
        String form = ((InternetAddress) address).getAddress();
        return form;
    }