我想安排发送电子邮件通知使用 Spring 启动，用户创建通知（主题，消息，发送日期…）

public class EmailNotification implements Serializable {
    /**
     * 
     */
    private static final long serialVersionUID = 3400952201530474821L;
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;
    private String subject;
    private String message;
    @Column(name = "sending_date")
    @Basic(fetch = FetchType.EAGER)
    private String sendingDate;

通常情况下，我会从db获得一个通知列表，我应该使用循环“for”发送每个通知，其中包含它自己的信息（由客户端指定），但是我发现发送时间有问题，我无法使用@scheduled注解，因为这里的cron表达式应该是动态的（从db检索）这里是我的方法：

public void periodicNotification()  {
        JavaMailSenderImpl jms = (JavaMailSenderImpl) sender;
        MimeMessage message = jms.createMimeMessage();
        MimeMessageHelper helper;
        try {
            helper = new MimeMessageHelper(message, MimeMessageHelper.MULTIPART_MODE_MIXED_RELATED, StandardCharsets.UTF_8.name());
        //get the list of notifs from the DB
        List<EmailNotification> emailNotifs = emailNotificationsRepo.findAll();
        for (EmailNotification i : emailNotifs) 
        {
            helper.setFrom("mail");
            List<String> recipients = fileRepo.findWantedEmails(i.getDaysNum());
            String[] to = recipients.stream().toArray(String[]::new);
            helper.setTo(to);
            helper.setText(i.getMessage());
            helper.setSubject(i.getSubject());
            sender.send(message);
            System.out.println("Email successfully sent to: " + Arrays.toString(to));
        }
        }
        catch (MessagingException e) {
            e.print...
        }
    }

我开始了这个方法：

public static void main(String[] args) {
        try {
            JobDetail job1 = JobBuilder.newJob(Job1.class).withIdentity("job1", "group1").build();
            Trigger trigger1 = TriggerBuilder.newTrigger().withIdentity("cronTrigger1", "group1")
                    .withSchedule(CronScheduleBuilder.cronSchedule("0/30 * * * * ?")).build();
            Scheduler scheduler1 = new StdSchedulerFactory().getScheduler();
            scheduler1.start();
            scheduler1.scheduleJob(job1, trigger1);
            Thread.sleep(100000);
            scheduler1.shutdown();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

但是我想在客户机指定的时间安排电子邮件的发送，在上面的方法中，cron表达式是静态的，这不是我想要的