Java Mail iCal会议邀请时区偏移问题详解与解决方案

import java.time.LocalDate;
import java.time.LocalTime;
import java.time.Month;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;

public class ICalTimeZoneExample {

    public static void main(String[] args) {
        // 假设的会议日期和时间
        LocalDate meetingDate = LocalDate.of(2020, Month.DECEMBER, 8);
        LocalTime meetingStartTime = LocalTime.of(4, 0); // 04:00
        LocalTime meetingEndTime = LocalTime.of(6, 0);   // 06:00

        // 指定会议所在的时区，例如“Europe/Berlin”
        ZoneId berlinZone = ZoneId.of("Europe/Berlin");

        // 创建ZonedDateTime对象，它包含了日期、时间以及时区信息
        ZonedDateTime startDateTime = ZonedDateTime.of(meetingDate, meetingStartTime, berlinZone);
        ZonedDateTime endDateTime = ZonedDateTime.of(meetingDate, meetingEndTime, berlinZone);

        // 定义iCal所需的日期时间格式 (YYYYMMDDTHHMMSS)
        // 注意：这里不再需要'Z'字符，因为我们通过TZID指定了时区
        DateTimeFormatter iCalFormatter = DateTimeFormatter.ofPattern("yyyyMMdd'T'HHmmss");

        // 格式化后的时间字符串
        String formattedStartDate = iCalFormatter.format(startDateTime);
        String formattedEndDate = iCalFormatter.format(endDateTime);

        // 生成DTSTART和DTEND属性字符串
        String dtStartString = String.format("DTSTART;TZID=%s:%s", startDateTime.getZone().getId(), formattedStartDate);
        String dtEndString = String.format("DTEND;TZID=%s:%s", endDateTime.getZone().getId(), formattedEndDate);

        System.out.println("生成的DTSTART字符串: " + dtStartString);
        System.out.println("生成的DTEND字符串: " + dtEndString);

        // 示例输出:
        // 生成的DTSTART字符串: DTSTART;TZID=Europe/Berlin:20201208T040000
        // 生成的DTEND字符串: DTEND;TZID=Europe/Berlin:20201208T060000
    }
}

import javax.activation.DataHandler;
import javax.mail.*;
import javax.mail.internet.*;
import javax.mail.util.ByteArrayDataSource;
import java.io.IOException;
import java.time.LocalDate;
import java.time.LocalTime;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Properties;

public class MeetingInviteSender {

    public static void main(String[] args) {
        // 邮件认证信息 (请替换为您的实际信息)
        final String username = "your_email@gmail.com";
        final String password = "your_app_password"; // 如果使用Gmail，可能是应用专用密码

        String from = "your_email@gmail.com";
        String to = "recipient_email@example.com";
        String subject = "Meeting Subject (Corrected Timezone)";
        String emailBody = "Hi Team, This is meeting description. Thanks";

        // 1. 定义会议的日期、时间以及所在时区
        LocalDate meetingDate = LocalDate.of(2020, Month.DECEMBER, 8);
        LocalTime meetingStartTime = LocalTime.of(4, 0); // 例如，柏林时间04:00
        LocalTime meetingEndTime = LocalTime.of(6, 0);   // 例如，柏林时间06:00
        ZoneId meetingZone = ZoneId.of("Europe/Berlin"); // 指定柏林时区

        // 2. 创建ZonedDateTime对象
        ZonedDateTime startDateTime = ZonedDateTime.of(meetingDate, meetingStartTime, meetingZone);
        ZonedDateTime endDateTime = ZonedDateTime.of(meetingDate, meetingEndTime, meetingZone);

        // 3. 定义iCal所需的日期时间格式 (不带'Z')
        DateTimeFormatter iCalFormatter = DateTimeFormatter.ofPattern("yyyyMMdd'T'HHmmss");

        // 4. 格式化时间字符串
        String formattedStartDate = iCalFormatter.format(startDateTime);
        String formattedEndDate = iCalFormatter.format(endDateTime);

        try {
            Properties prop = new Properties();
            prop.put("mail.smtp.auth", "true");
            prop.put("mail.smtp.starttls.enable", "true");
            prop.put("mail.smtp.host", "smtp.gmail.com");
            prop.put("mail.smtp.port", "587"); // 通常Gmail使用587端口进行TLS

            Session session = Session.getInstance(prop, new javax.mail.Authenticator() {
                protected PasswordAuthentication getPasswordAuthentication() {
                    return new PasswordAuthentication(username, password);
                }
            });

            MimeMessage message = new MimeMessage(session);
            message.addHeaderLine("method=REQUEST");
            message.addHeaderLine("charset=UTF-8");
            message.addHeaderLine("component=VEVENT");

            message.setFrom(new InternetAddress(from, "New Outlook Event"));
            message.addRecipient(Message.RecipientType.TO, new InternetAddress(to));
            message.setSubject(subject);

            StringBuffer sb = new StringBuffer();
            StringBuffer buffer = sb.append("BEGIN:VCALENDAR\n" +
                    "PRODID:-//Microsoft Corporation//Outlook 9.0 MIMEDIR//EN\n" +
                    "VERSION:2.0\n" +
                    "METHOD:REQUEST\n" +
                    "BEGIN:VEVENT\n" +
                    "ATTENDEE;ROLE=REQ-PARTICIPANT;RSVP=TRUE:MAILTO:" + to + "\n" +
                    // 关键修改：使用TZID和格式化后的本地时间
                    "DTSTART;TZID=" + startDateTime.getZone().getId() + ":" + formattedStartDate + "\n" +
                    "DTEND;TZID=" + endDateTime.getZone().getId() + ":" + formattedEndDate + "\n" +
                    "LOCATION:Conference room\n" +
                    "TRANSP:OPAQUE\n" +
                    "SEQUENCE:0\n" +
                    "UID:040000008200E00074C5B7101A82E00800000000002FF466CE3AC5010000000000000000100\n" +
                    " 000004377FE5C37984842BF9440448399EB02\n" + // UID通常需要是唯一的，这里仅为示例
                    "CATEGORIES:Meeting\n" +
                    "DESCRIPTION:" + emailBody + "\n\n" +
                    "SUMMARY:Test meeting request\n" +
                    "PRIORITY:5\n" +
                    "CLASS:PUBLIC\n" +
                    "BEGIN:VALARM\n" +
                    "TRIGGER:PT1440M\n" +
                    "ACTION:DISPLAY\n" +
                    "DESCRIPTION:Reminder\n" +
                    "END:VALARM\n" +
                    "END:VEVENT\n" +
                    "END:VCALENDAR");

            // Create the message part
            BodyPart messageBodyPart = new MimeBodyPart();

            // Fill the message
            messageBodyPart.setHeader("Content-Class", "urn:content-classes:calendarmessage");
            messageBodyPart.setHeader("Content-ID", "calendar_message");
            messageBodyPart.setDataHandler(new DataHandler(
                    new ByteArrayDataSource(buffer.toString(), "text/calendar")));// very important

            // Create a Multipart
            Multipart multipart = new MimeMultipart();

            // Add part one
            multipart.addBodyPart(messageBodyPart);

            // Put parts in message
            message.setContent(multipart);

            // send message
            Transport.send(message);

            System.out.println("Email sent!");
        } catch (MessagingException me) {
            me.printStackTrace();
        } catch (IOException ex) {
            ex.printStackTrace();
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }
}