How to send Email in Specific time interval continously Using Timer threads

How to send Email in Specific time interval continously Using Timer

FreeMarker is a "template engine"; a generic tool to generate text output (anything from HTML to autogenerated source code) based on templates. It's a Java package, a class library for Java programmers. It's not an application for end-users in itself, but something that programmers can embed into their products. 

reference(http://freemarker.sourceforge.net/)

I am using freemarker template for creating the email body. I have used my gmail a/c username and password for the email send test purpose. So if you want to execute your program then in the Constant.java file use your gmail username and password for FROM_MAIL_ID and FROM_MAIL_ID_PASS property.

Before going through the below program few jars are required, the references are given below:-

1) http://www.java2s.com/Code/Jar/a/Downloadactivationjar.htm - activation.jar

2) mirrors.ibiblio.org/pub/mirrors/maven2/freemarker/freemarker/2.3.4/freemarker-2.3.4.jar - freemarker.jar

3) http://www.java2s.com/Code/Jar/m/Downloadmailjar.htm - mail.jar

STEP - 1

1) Create java file and name it as Constants.java file as below:-

package com.gaurav.examples.mail;

public class Constants
{
    public static final String TEMPLATE_FILENAME = "html-mail-template.ftl";
    public static final String ATTACHMENT_FILENAME = "welcome.txt";
    public static final String MAIL_SEND_SUCCESS_STATUS = "mail Sent successfully";
    public static final String MAIL_SEND_SUCCESS_FAIL = "mail send failed";
    public static final String FROM_MAIL_ID = "test@gmail.com";//This is From mail-id.
    public static final String FROM_MAIL_ID_PASS ="Please keep ur password here";//From Mail-id password.
    public static final String TO_MAIL_ID = "tomailIdUsername@gmail.com";//Please use to mail id here.
    public static final String MAIL_SUBJECT = "Sending a Test mail through Java Mail API";
    public static final String TO_MAIL = "to";
    public static final String TO_MAIL_NAME = "Gollu";
    public static final String MAIL_BODY = "body";
    public static final String EMAIL_BODY_CONTENT = "See the text file and reply the answer?";
    public static final String FROM_MAIL = "from";
    public static final String FROM_MAIL_NAME = "Kumar.";
    public static final String PROPERTY_FILENAME ="settings.properties";
    public static final String BODY_CONTENT_TYPE="text/html";
}

STEP - 2

1) Create a java file and name it as SendMail.java, use the below contents

 

package com.gaurav.examples.mail;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.StringWriter;
import java.io.Writer;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;

import javax.activation.DataHandler;
import javax.activation.DataSource;
import javax.activation.FileDataSource;
import javax.mail.Authenticator;
import javax.mail.BodyPart;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.Multipart;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;

import freemarker.template.Configuration;
import freemarker.template.Template;

public class SendMail {

    private String strMailSendStatus = null;

    public String mailSend() throws Exception {

        Properties props = new Properties();
        try {
            props.load(new FileInputStream(
                    new File(Constants.PROPERTY_FILENAME)));
        } catch (FileNotFoundException e1) {
            e1.printStackTrace();
        } catch (IOException e1) {
            e1.printStackTrace();
        }

        Session session = Session.getDefaultInstance(props,
                new Authenticator() {

                    protected PasswordAuthentication getPasswordAuthentication() {
                        return new PasswordAuthentication(
                                Constants.FROM_MAIL_ID,
                                Constants.FROM_MAIL_ID_PASS);
                    }
                });

        try {
            Message message = new MimeMessage(session);

            message.setFrom(new InternetAddress());
            message.setRecipients(Message.RecipientType.TO,
                    InternetAddress.parse(Constants.TO_MAIL_ID));
            message.setSubject(Constants.MAIL_SUBJECT);

            BodyPart body = new MimeBodyPart();

            // freemarker api use for using it's template.
            Configuration cfg = new Configuration();
            Template template = cfg.getTemplate(Constants.TEMPLATE_FILENAME);
            Map<String, String> rootMap = new HashMap<String, String>();
            rootMap.put(Constants.TO_MAIL, Constants.TO_MAIL_NAME);
            rootMap.put(Constants.MAIL_BODY, Constants.EMAIL_BODY_CONTENT);
            rootMap.put(Constants.FROM_MAIL, Constants.FROM_MAIL_NAME);
            Writer out = new StringWriter();
            template.process(rootMap, out);
            // freemarker api use for using it's template ends here.

            /* we can keep html tags in our text for the decoration purpose. */
            body.setContent(out.toString(), "text/html");

            Multipart multipart = new MimeMultipart();
            multipart.addBodyPart(body);

            body = new MimeBodyPart();

            String filename = Constants.ATTACHMENT_FILENAME;
            DataSource source = new FileDataSource(filename);
            body.setDataHandler(new DataHandler(source));
            body.setFileName(filename);
            multipart.addBodyPart(body);

            message.setContent(multipart, "text/html");

            Transport.send(message);

            strMailSendStatus = Constants.MAIL_SEND_SUCCESS_STATUS;

        } catch (MessagingException e) {
            e.printStackTrace();
            strMailSendStatus = Constants.MAIL_SEND_SUCCESS_FAIL;
        }

        return strMailSendStatus;
    }
}
 

STEP - 3

1) Create a java file and name it as SendMailCaller.java as below

package com.gaurav.examples.mail;

import java.util.TimerTask;


public class SendMailCaller extends TimerTask
{

    public void run()
    {

        SendMail sender = new SendMail();
                String mailSendStatus = null;
                try{
                    mailSendStatus = sender.mailSend();
                }catch(Exception e){
                    e.printStackTrace();
                }
               System.out.println("Email Sent status ->"+mailSendStatus);

            }
}

STEP - 4 

1) Create a java file and name it as EmailJobScheduler.java like below:-

package com.gaurav.examples.mail;

import java.util.Timer;

public class EmailJobScheduler {

    public void callScheduler() throws Exception {

        System.out.println("Scheduler Starterd...");
        Timer timer = new Timer();
        timer.scheduleAtFixedRate(new SendMailCaller(), getTimeDelayAndPeriod("2s"),
                getTimeDelayAndPeriod("10s"));

    }

    public long getTimeDelayAndPeriod(String value) throws Exception {
        long l = 0;
        String val = "";
        try {
            if (value.endsWith("d") || value.endsWith("D")) {
                val = value.substring(0, value.length() - 1);
                l = Long.parseLong(val) * 24 * 60 * 60 * 1000;
            }

            else if (value.endsWith("h") || value.endsWith("H")) {

                val = value.substring(0, value.length() - 1);
                l = Long.parseLong(val) * 60 * 60 * 1000;

            } else if (value.endsWith("m") || value.endsWith("M")) {
                val = value.substring(0, value.length() - 1);
                l = Long.parseLong(val) * 60 * 1000;
            } else if (value.endsWith("s") || value.endsWith("S")) {

                val = value.substring(0, value.length() - 1);
                l = Long.parseLong(val) * 1000;
            } else {

                l = Long.parseLong(value);
            }

        } catch (Exception e) {

            throw new Exception(e);
        }

        return l;
    }

    public static void main(String a[]) throws Exception {
        EmailJobScheduler emailJobScheduler = new EmailJobScheduler();
        emailJobScheduler.callScheduler();
    }

}

STEP - 5

1) Create a file and name it as html-mail-template.ftl, use the below contents:-

<html>
<body>
Hi ${to},

<p style='color:midnightblue;'>${body}</p>

Regards,<br/>
${from}.
</body>
</html>

STEP - 6

1) Create a text file and name it as welcome.txt, use the below content:-

Who is elected as the president of India in 2012?

STEP - 7

1) Create a file and name it as settings.properties, and use the below content:

mail.smtp.socketFactory.class=javax.net.ssl.SSLSocketFactory

mail.smtp.auth=true
mail.smtp.port=465
mail.smtp.host=smtp.gmail.com
mail.smtp.socketFactory.port=465

STEP - 8

In order to run  this application three external jars are required which is as below:-

Required Jars    -       (download link)

activation.jar - http://www.java2s.com/Code/Jar/a/Downloadactivationjar.htm

freemarker.jar - http://www.java2s.com/Code/Jar/f/Downloadfreemarker2316jar.htm

mail.jar - http://www.java2s.com/Code/Jar/m/Downloadmailjar.htm

References are given above.

The project directory structure is given below:-