java - 如何每天在特定时间使用java发送邮件

Question

我正在开发一个使用 Java、servlet、JSP 并使用 apache Tomcat 作为应用服务器的 web_application

我做了什么

• 我创建了一个UI，用户可以在其中选择邮件 ID(他们可以选择多个)
• 当用户点击发送按钮时，我会触发我的 java 类并发送邮件

现在我要做的

• 现在我必须动态地执行此操作，每天晚上 12:00 我必须向某些特定用户发送邮件

• 我必须向其发送邮件的用户我正在从登录查询中获取该邮件 ID，因此这不是问题

• 我只想知道半夜12:00怎么发邮件

我到现在为止做过的编码

servlet 类

public class EmailSendingServlet extends HttpServlet {

private static final long serialVersionUID = 1L;
private String host;
private String port;
private String user;
private String pass;

public void init() {

    ServletContext context = getServletContext();
    host = context.getInitParameter("host");
    port = context.getInitParameter("port");
    user = context.getInitParameter("user");
    pass = context.getInitParameter("pass");
}

protected void doPost(HttpServletRequest request,
        HttpServletResponse response) throws ServletException, IOException {
    String recipient = request.getParameter("To"); // this i will get from login query
    String subject = request.getParameter("subject");//this i can define manually
    String content = request.getParameter("content");//same for this also


    String resultMessage = "";

    try {
        EmailUtility.sendEmail(host, port, user, pass, recipient, subject,
                content);
        resultMessage = "The e-mail was sent successfully";
    } catch (Exception ex) {
        ex.printStackTrace();
        resultMessage = "There were an error: " + ex.getMessage();
    } 
}

Java 实用类

public class EmailUtility {
public static void sendEmail(String host, String port, final String userName, final String password,
        String toAddress, String subject, String message) throws AddressException, MessagingException {


    Properties properties = new Properties();
    properties.put("mail.smtp.host", host);
    properties.put("mail.smtp.port", port);
    properties.put("mail.smtp.auth", "true");
    properties.put("mail.smtp.starttls.enable", "true");
    Session session = Session.getDefaultInstance(properties, new javax.mail.Authenticator() {
        protected PasswordAuthentication getPasswordAuthentication() {
            return new PasswordAuthentication(userName, password);
        }
    });
    session.setDebug(false);
    Message msg = new MimeMessage(session);

    msg.setFrom(new InternetAddress(userName));
    if (toAddress!= null) {
        List<String> emails = new ArrayList<>();
        if (toAddress.contains(",")) {
            emails.addAll(Arrays.asList(toAddress.split(",")));
        } else {
            emails.add(toAddress);
        }
        Address[] to = new Address[emails.size()];
        int counter = 0;
        for(String email : emails) {
            to[counter] = new InternetAddress(email.trim());
            counter++;
        }
        msg.setRecipients(Message.RecipientType.TO, to);
    }
    msg.setSubject(subject);
    msg.setSentDate(new Date());
    msg.setText(message);

    Transport.send(msg);

}

Answer 1

您可以使用 ScheduledExecutorService 在“普通”Java 中处理此问题:

 ScheduledExecutorService ses = Executors.newScheduledThreadPool(1);
 int count = 0;

        Runnable task = () -> {
            count++;
            System.out.println(count);
        };

        ScheduledFuture<?> scheduledFuture = ses.scheduleAtFixedRate(task, 12, TimeUnit.HOURS);

还有一种使用初始延迟的方法，但您可以在此处阅读更多内容: https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ScheduledExecutorService.html

对于您的用例:

引入一个新类EmailSendJobUtil:

public class EmailSendUtil {
  public void createAndSubmitSheduledJob() {
   ScheduledExecutorService ses = Executors.sheduledThreadPool(1);
   ScheduledFuture<> sheduledFuture = ses.sheduleAtFixedRate(EmailUtility.sendMail(), 12, TimeUnit.HOURS);
  }
}

但是，您会遇到代码结构方面的问题。尝试在您的 EmailUtility 中引入一种封装自动发送邮件的方法。

引入一个存储库来保存您必须自动向哪些用户发送邮件，并以仅处理自动发送的新方法读取此数据。你可以这样做:

public class MailJobRepository {
  private List<MailJob> jobs;

  void add();
  void remove();
  List<> getJobs();
}

并在您的 EmailUtility 中引入一个新方法:

public void sendAutomatedEmails() {
  jobRepository.getJobs().foreach(job -> {
   sendMail(job.getToAddress(), job.getSubject(), job.getMessage());
  });
}

然后您可以调度这个新方法，并且您已将代码拆分为逻辑上独立的部分。

一点提示:

String host, String port, final String userName, final String password  

这是您发送电子邮件的“一方”的数据，不应作为方法参数传递。您可以将此数据保存到您的 EmailUtility 类中。