JavaMail读取收件箱退信邮件/分析邮件附件获取Message_Id

需求描述：公司最近有个项目邮件通知功能，但是客户上传的邮件地址并不一定存在，以及其他的各种问题。所有希望发送通知后有个回执，及时发现地址存在问题的邮箱。

需求分析：经过分析JavaMail可以读取收件箱邮件，我们可以通过对应通知的退信来回写通知状态。那么问题来了，发送通知和退信如何建立映射？经过调研，最终确定采用以下方案解决。

映射方案：

1. 在发送邮件通知时在Header中指定自定义的Message_Id，作为唯一标示，本系统中采用UUID。
2. 定时任务扫描服务器邮箱的收件箱，本系统我们搜索收件箱中前30分钟内的主题为：“来自postmaster@net.cn的退信”,的退信邮件。
3. 分析退信附件，退信关联邮件信息存在附件中，我们需要的Message_Id也在其中，解析附件获取Message_Id回写通知状态。

核心代码：

邮件搜索

package com.yinghuo.yingxinxin.notification.service;

import com.yinghuo.yingxinxin.notification.domain.PayrollNotificationEntity;
import com.yinghuo.yingxinxin.notification.domain.valobj.EmailNotificationStatus;
import com.yinghuo.yingxinxin.notification.repository.NotificationRepository;
import com.yinghuo.yingxinxin.notification.util.DateUtil;
import com.yinghuo.yingxinxin.notification.util.EmailUtil;
import com.yinghuo.yingxinxin.notification.util.StringUtil;
import lombok.Data;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang.exception.ExceptionUtils;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.mail.*;
import javax.mail.search.AndTerm;
import javax.mail.search.ComparisonTerm;
import javax.mail.search.SearchTerm;
import javax.mail.search.SentDateTerm;
import javax.mail.search.SubjectTerm;
import java.util.Arrays;
import java.util.Calendar;
import java.util.Date;
import java.util.Properties;

@Service
@Slf4j
@Data
@ConfigurationProperties(prefix = "spring.mail")
public class EmailBounceScanService {
    private final static String subjectKeyword = "来自postmaster@net.cn的退信";

    private String popHost;
    private String username;
    private String password;
    private Integer timeOffset;
    private final NotificationRepository payrollSendRecordRepository;

    private Properties buildInboxProperties() {
        Properties properties = new Properties();
        properties.setProperty("mail.store.protocol", "pop3");
        properties.setProperty("mail.pop3.host", popHost);
        properties.setProperty("mail.pop3.auth", "true");
        properties.setProperty("mail.pop3.default-encoding", "UTF-8");
        return properties;
    }

    public void searchInboxEmail() {
        Session session = Session.getInstance(this.buildInboxProperties());
        Store store = null;
        Folder receiveFolder = null;
        try {
            store = session.getStore("pop3");
            store.connect(username, password);
            receiveFolder = store.getFolder("inbox");
            receiveFolder.open(Folder.READ_ONLY);

            int messageCount = receiveFolder.getMessageCount();
            if (messageCount > 0) {
                Date now = Calendar.getInstance().getTime();
                Date timeOffsetAgo = DateUtil.nextXMinute(now, timeOffset);
                SearchTerm comparisonTermGe = new SentDateTerm(ComparisonTerm.GE, timeOffsetAgo);
                SearchTerm search = new AndTerm(new SubjectTerm(subjectKeyword), comparisonTermGe);

                Message[] messages = receiveFolder.search(search);
                if (messages.length == 0) {
                    log.info("No bounce email was found.");
                    return;
                }
                this.messageHandler(messages);
            }
        } catch (MessagingException e) {
            log.error("Exception in searchInboxEmail {}", ExceptionUtils.getFullStackTrace(e));
            e.printStackTrace();
        } finally {
            try {
                if (receiveFolder != null) {
                    receiveFolder.close(true);
                }
                if (store != null) {
                    store.close();
                }
            } catch (MessagingException e) {
                log.error("Exception in searchInboxEmail {}", ExceptionUtils.getFullStackTrace(e));
                e.printStackTrace();
            }
        }
    }

    @Transactional
    public void messageHandler(Message[] messageArray) {
        Arrays.stream(messageArray).filter(EmailUtil::isContainAttachment).forEach((message -> {
            String messageId = null;
            try {
                messageId = EmailUtil.getMessageId(message);
            } catch (Exception e) {
                log.error("getMessageId:", ExceptionUtils.getFullStackTrace(e));
                e.printStackTrace();
            }
            if (StringUtil.isEmpty(messageId)) return;

            PayrollNotificationEntity payrollNotificationEntity = payrollSendRecordRepository.findFirstByMessageId(messageId);
            if (payrollNotificationEntity == null || EmailNotificationStatus.BOUNCE.getStatus() == payrollNotificationEntity.getStatus()) {
                log.warn("not found payrollNotificationEntity by messageId:{}", messageId);
                return;
            }

            payrollNotificationEntity.setStatus(EmailNotificationStatus.BOUNCE.getStatus());
            payrollNotificationEntity.setErrorMessage(EmailNotificationStatus.BOUNCE.getErrorMessage());
            payrollSendRecordRepository.save(payrollNotificationEntity);
        }));
    }
}

附件解析

package com.yinghuo.yingxinxin.notification.util;

import lombok.extern.slf4j.Slf4j;

import javax.mail.BodyPart;
import javax.mail.MessagingException;
import javax.mail.Multipart;
import javax.mail.Part;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

@Slf4j
public final class EmailUtil {
    private static final String multipart = "multipart/*";

    public static String getMessageId(Part part) throws Exception {
        if (!part.isMimeType(multipart)) {
            return "";
        }

        Multipart multipart = (Multipart) part.getContent();
        for (int i = 0; i < multipart.getCount(); i++) {
            BodyPart bodyPart = multipart.getBodyPart(i);

            if (part.isMimeType("message/rfc822")) {
                return getMessageId((Part) part.getContent());
            }
            InputStream inputStream = bodyPart.getInputStream();

            try (BufferedReader br = new BufferedReader(new InputStreamReader(inputStream))) {
                String strLine;
                while ((strLine = br.readLine()) != null) {
                    if (strLine.startsWith("Message_Id:")) {
                        String[] split = strLine.split("Message_Id:");
                        return split.length > 1 ? split[1].trim() : null;
                    }
                }
            }
        }

        return "";
    }

    public static boolean isContainAttachment(Part part) {
        boolean attachFlag = false;
        try {
            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 = isContainAttachment((Part) mpart);
                    } else {
                        String contype = mpart.getContentType();
                        if (contype.toLowerCase().contains("application"))
                            attachFlag = true;
                        if (contype.toLowerCase().contains("name"))
                            attachFlag = true;
                    }
                }
            } else if (part.isMimeType("message/rfc822")) {
                attachFlag = isContainAttachment((Part) part.getContent());
            }
        } catch (MessagingException | IOException e) {
            e.printStackTrace();
        }
        return attachFlag;
    }
}