Send Email in Specific time

Question

I use below code to send an Email. Just create an object and call the method of that object.

package com.kap.globalreport;
public class Mainmethod930 { 
    public static void main(String[] args) {
        EmailReport930 emailReport930 = new EmailReport930();
        emailReport930.sendEmail("emailContent","Subject");
    }
}

above I create object and call below sendEmail method.

package com.kap.globalreport;

import javax.mail.*;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;
import java.util.Date;
import java.util.Properties;

public class EmailReport930 implements Runnable {

final private String SMTP_SERVER = "166.62.121.14";
final private String SMTP_PORT = "587";
final private String ROWEL_EMAIL = "dumidu@kapruka.com";
final private String FROM_EMAIL = "cargillspaymenterros@kapruka.com";
final private String FROM_EMAIL_PASSWORD = "cpay@55";
private String emailContent;
private String subject;

public String getEmailContent() {
    return emailContent;
}

public void setEmailContent(String emailContent) {
    this.emailContent = emailContent;
}

public String getSubject() {
    return subject;
}

public void setSubject(String subject) {
    this.subject = subject;
}

private void setEmail(String emailContent, String subject) {
    if (emailContent != null && subject != null) {
        sendEmail(emailContent, subject);
    }
}

public void sendEmail(String emailContent, String subject) {
    try {

        Properties props = new Properties();
        props.put("mail.transport.protocol", "smtp");
        props.put("mail.smtp.host", SMTP_SERVER);
        props.put("mail.smtp.port", SMTP_PORT);
        props.put("mail.smtp.auth", "true");
        Session mailSession = Session.getInstance(props, new Authenticator() {
            @Override
            public PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication(FROM_EMAIL, FROM_EMAIL_PASSWORD);
            }
        });
        mailSession.setDebug(true);
        MimeMessage message = new MimeMessage(mailSession);
        message.setFrom(new InternetAddress(FROM_EMAIL));
        message.addHeader("site", "kapruka.com");
        message.addHeader("service", "Cargills Payment Service");
        message.setSentDate(new Date());
        message.addRecipient(Message.RecipientType.TO, new InternetAddress(ROWEL_EMAIL));
        message.setSubject(subject);

        MimeMultipart mimeMultipart = new MimeMultipart();
        BodyPart messageBodyPart = new MimeBodyPart();
        messageBodyPart.setContent(emailContent, "text/html; charset=utf-8");
        messageBodyPart.setContent("<h1>SMTP_PORT</h1>", "text/html");
        mimeMultipart.addBodyPart(messageBodyPart);
        message.setContent(mimeMultipart);

        Transport.send(message);
        System.out.println("Email Sent successfully....");

    } catch (MessagingException mex) {
        mex.printStackTrace();
    }
}

@Override
public void run() {
    setEmail(emailContent, subject);
}
}

I want to run this send email method in specific time.I also want to get data from data base using hibernate framework. Email should be send with above data.

Answer 1

Normally there are four different ways to running a task periodically:

1. Timer
2. ScheduledExecutorService
3. Spring Scheduler
4. Quartz

In your case since you are not using any framework, you could do it using native java with timer and ScheduledExecutorService as:

public class PeriodicTask {
    public static void main(String... args) {
        // System.out.println(LocalTime.ofSecondOfDay(getDelayTo(15, 4)));
        // System.out.println(LocalTime.ofSecondOfDay(getDelayTo(16, 4)));
        testTimer();
        testScheduledExecutorService();
    }

    private static long getDelayTo(int hour, int minute) {
        LocalDateTime currentTime = LocalDateTime.now();
        long gapToSpecified = ChronoUnit.SECONDS.between(currentTime, LocalDate.now().atTime(hour, minute));
        if (gapToSpecified < 0) { // the time already passed => do it tomorrow;
            return ChronoUnit.SECONDS.between(currentTime, LocalDate.now().plusDays(1).atTime(hour, minute));
        }
        return gapToSpecified; // not passed, do it later today at the specified time;
    }

    public static void testTimer() {
        new Timer().schedule(new TimerTask() {
            @Override
            public void run() {
                System.out.println(LocalDateTime.now());
                System.out.println("Hello world");
            }
        }, getDelayTo(13, 0), TimeUnit.DAYS.toSeconds(1));
    }

    public static void testScheduledExecutorService() {
        Executors.newScheduledThreadPool(1).scheduleWithFixedDelay(() -> {
                    System.out.println("Hello World!");
                }, getDelayTo(13, 0), TimeUnit.DAYS.toSeconds(1), TimeUnit.SECONDS);
    }
}

Answer 2

Use a java.util.Timer and schedule your work.

Timer.schedule(TimerTask task, Date firstTime, long period)

_{~ Timer (Java Platform SE 7 ) ~}

Calendar c = Calendar.getInstance();
c.set(Calendar.HOUR_OF_DAY, 13);
c.set(Calendar.MINUTE, 00);
c.set(Calendar.SECOND, 00);

Timer timer = new Timer();
timer.schedule(new TimerTask() {
    @Override
    public void run() {
        //Call your method here
        //setEmail(emailContent, subject);
    }
}, c.getTime(), 86400000);

//24hrs == 86400000ms