Kode Java - Learn Java by Examples

How do I send email using Gmail via SSL?

By I Wayan Saryada in Mail Last modified: June 4, 2023 2 Comments

In another example you’ve seen how to send email using Gmail SMTP via TLS. See the following example How do I send email using Gmail via TLS?.

In this example you will use the SSL connection to connect to Gmail SMTP server. The difference with this is in the properties / configuration that we used to create the mail session object.

package org.kodejava.mail;

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

public class GmailSendEmailSSL {
    private static final String USERNAME = "[email protected]";
    private static final String PASSWORD = "password";

    public static void main(String[] args) throws Exception {
        // Email information such as from, to, subject and contents.
        String mailFrom = "[email protected]";
        String mailTo = "[email protected]";
        String mailSubject = "SSL - Gmail Send Email Demo";
        String mailText = "SSL - Gmail Send Email Demo";

        GmailSendEmailSSL gmail = new GmailSendEmailSSL();
        gmail.sendMail(mailFrom, mailTo, mailSubject, mailText);
    }

    private void sendMail(String mailFrom, String mailTo, String mailSubject,
                          String mailText) throws Exception {

        Properties config = createConfiguration();

        // Creates a mail session. We need to supply username and
        // password for Gmail authentication.
        Session session = Session.getInstance(config, new Authenticator() {
            @Override
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication(
                        GmailSendEmailSSL.USERNAME,
                        GmailSendEmailSSL.PASSWORD
                );
            }
        });

        // Creates email message
        Message message = new MimeMessage(session);
        message.setSentDate(new Date());
        message.setFrom(new InternetAddress(mailFrom));
        message.setRecipient(Message.RecipientType.TO, new InternetAddress(mailTo));
        message.setSubject(mailSubject);
        message.setText(mailText);

        // Send a message
        Transport.send(message);
    }

    private Properties createConfiguration() {
        return new Properties() {{
            put("mail.smtp.host", "smtp.gmail.com");
            put("mail.smtp.auth", "true");
            put("mail.smtp.port", "465");
            put("mail.smtp.socketFactory.port", "465");
            put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
            put("mail.smtp.ssl.protocols", "TLSv1.2");
        }};
    }
}

There is a chance that you can get an error that tell you cannot connect to the smtp.gmail.com port 465. If this is the case please check your connection to the server using telnet command. The command is telnet smtp.gmail.com 465, and see if there is a reply.

Maven Dependencies

<dependencies>
    <dependency>
        <groupId>javax.mail</groupId>
        <artifactId>javax.mail-api</artifactId>
        <version>1.5.6</version>
    </dependency>
    <dependency>
        <groupId>javax.mail</groupId>
        <artifactId>mail</artifactId>
        <version>1.4.7</version>
    </dependency>
</dependencies>

How do I send email using Gmail via TLS?

By I Wayan Saryada in Mail Last modified: June 4, 2023 3 Comments

The following example show you how to send email using Gmail SMTP via TLS connection. The username and password is used to authenticate you against the Gmail.

The configuration / properties used for connection to the Gmail SMTP is defined in the createConfiguration() method. The properties include information such as the SMTP host address, port number, etc.

To send email using Gmail via SSL see the following code snippet How do I send email using Gmail via SSL?.

Let’s see the code snippet below:

package org.kodejava.mail;

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

public class GmailSendEmailTLS {
    private static final String USERNAME = "[email protected]";
    private static final String PASSWORD = "password";

    public static void main(String[] args) throws Exception {
        // Email information such as from, to, subject and contents.
        String mailFrom = "[email protected]";
        String mailTo = "[email protected]";
        String mailSubject = "TLS - Gmail Send Email Demo";
        String mailText = "TLS - Gmail Send Email Demo";

        GmailSendEmailTLS gmail = new GmailSendEmailTLS();
        gmail.sendMail(mailFrom, mailTo, mailSubject, mailText);
    }

    private void sendMail(String mailFrom, String mailTo, String mailSubject,
                          String mailText) throws Exception {

        Properties config = createConfiguration();

        // Creates a mail session. We need to supply username and
        // password for Gmail authentication.
        Session session = Session.getInstance(config, new Authenticator() {
            @Override
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication(
                        GmailSendEmailTLS.USERNAME,
                        GmailSendEmailTLS.PASSWORD
                );
            }
        });

        // Creates email message
        Message message = new MimeMessage(session);
        message.setSentDate(new Date());
        message.setFrom(new InternetAddress(mailFrom));
        message.setRecipient(Message.RecipientType.TO,
                new InternetAddress(mailTo));
        message.setSubject(mailSubject);
        message.setText(mailText);

        // Send a message
        Transport.send(message);
    }

    private Properties createConfiguration() {
        return new Properties() {{
            put("mail.smtp.auth", "true");
            put("mail.smtp.host", "smtp.gmail.com");
            put("mail.smtp.port", "587");
            put("mail.smtp.starttls.enable", "true");
            put("mail.smtp.ssl.protocols", "TLSv1.2");
        }};
    }
}

Maven Dependencies

<dependencies>
    <dependency>
        <groupId>javax.mail</groupId>
        <artifactId>javax.mail-api</artifactId>
        <version>1.5.6</version>
    </dependency>
    <dependency>
        <groupId>javax.mail</groupId>
        <artifactId>mail</artifactId>
        <version>1.4.7</version>
    </dependency>
</dependencies>

How do I create default init-method and destroy method in Spring?

By I Wayan Saryada in Spring Core Last modified: June 4, 2023 0 Comment

When many beans in a context definition will have the same initialization and destroy method name, you can define a default-init-method and default-destroy-method in the attributes of the beans element.

This way you don’t have to define individual init-method and destroy-method for each of your beans. When the beans do not supply the method that match the name of defined default-init-method or default-destroy-method nothing will happen to those beans.

Let’s see an example code below. Firs here is our simple bean, the AutoEngine bean.

package org.kodejava.spring.core;

public class AutoEngine {
    public void initialize() {
        System.out.println("AutoEngine.initialize");
    }

    public void destroy() {
        System.out.println("AutoEngine.destroy");
    }
}

And then we define our Spring configuration file. You can see that there are default-init-method and default-destroy-method in the attribute of the beans element.

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"
       default-init-method="initialize" default-destroy-method="destroy">

    <bean id="engine" class="org.kodejava.spring.core.AutoEngine" />

</beans>

And finally a small program to run our demo.

package org.kodejava.spring.core;

import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class DefaultInitDestroyDemo {
    public static void main(String[] args) {
        ConfigurableApplicationContext context =
                new ClassPathXmlApplicationContext("default-init-destroy.xml");

        AutoEngine engine = (AutoEngine) context.getBean("engine");

        // context.close will remove the bean from the container.
        // This will call our bean destroy method.
        context.close();
    }
}

When you run this example you’ll get the following output printed on your screen:

AutoEngine.initialize
AutoEngine.destroy

Maven Dependencies

<dependencies>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>5.3.23</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-beans</artifactId>
        <version>5.3.23</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context-support</artifactId>
        <version>5.3.23</version>
    </dependency>
</dependencies>

How do I validate email address using Java Mail API?

By I Wayan Saryada in Mail Last modified: June 4, 2023 0 Comment

This code snippet shows you how to validate an email address using the javax.mail.internet.InternetAddress class. The validate() method throws a javax.mail.internet.AddressException when the email address passed to the constructor is not a valid email address.

Here is the complete code snippet:

package org.kodejava.mail;

import javax.mail.internet.AddressException;
import javax.mail.internet.InternetAddress;

public class ValidateEmail {
    public static void main(String[] args) {
        ValidateEmail demo = new ValidateEmail();

        String email = "[email protected]";
        boolean isValid = demo.validateEmail(email);
        demo.printStatus(email, isValid);

        email = "kodejava.example";
        isValid = demo.validateEmail(email);
        demo.printStatus(email, isValid);
    }

    private boolean validateEmail(String email) {
        boolean isValid = false;
        try {
            // Create InternetAddress object and validated the supplied
            // address which is this case is an email address.
            InternetAddress internetAddress = new InternetAddress(email);
            internetAddress.validate();
            isValid = true;
        } catch (AddressException e) {
            e.printStackTrace();
        }
        return isValid;
    }

    private void printStatus(String email, boolean valid) {
        System.out.println(email + " is " + (valid ? "a" : "not a") +
                " valid email address");
    }
}

When running the program you will get the following message printed on the screen.

[email protected] is a valid email address
kodejava.example is not a valid email address
javax.mail.internet.AddressException: Missing final '@domain' in string ``kodejava.example''
    at javax.mail.internet.InternetAddress.checkAddress(InternetAddress.java:1279)
    at javax.mail.internet.InternetAddress.validate(InternetAddress.java:1154)
    at org.kodejava.mail.ValidateEmail.validateEmail(ValidateEmail.java:25)
    at org.kodejava.mail.ValidateEmail.main(ValidateEmail.java:15)

Maven Dependencies

<dependencies>
    <dependency>
        <groupId>javax.mail</groupId>
        <artifactId>javax.mail-api</artifactId>
        <version>1.5.6</version>
    </dependency>
    <dependency>
        <groupId>javax.mail</groupId>
        <artifactId>mail</artifactId>
        <version>1.4.7</version>
    </dependency>
</dependencies>

How do I read file using FileInputStream?

By I Wayan Saryada in Core API, IO Last modified: June 4, 2023 0 Comment

The following example use the java.io.FileInputStream class to read contents of a text file. We’ll read a file located in the temporary directory defined by operating system. This temporary directory can be accessed using the java.io.tmpdir system property.

package org.kodejava.io;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;

public class FileInputStreamDemo {
    public static void main(String[] args) {
        // Get the temporary directory. We'll read the data.txt file
        // from this directory.
        String tempDir = System.getProperty("java.io.tmpdir");
        File file = new File(tempDir + "/data.txt");

        StringBuilder builder = new StringBuilder();
        FileInputStream fis = null;
        try {
            // Create a FileInputStream to read the file.
            fis = new FileInputStream(file);

            int data;
            // Read the entire file data. When -1 is returned it
            // means no more content to read.
            while ((data = fis.read()) != -1) {
                builder.append((char) data);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (fis != null) {
                try {
                    fis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

        // Print the content of the file
        System.out.println("File Contents = " + builder);
    }
}

The content read from the input stream will be appended into a StringBuilder object. At the end of the snippet the content of the will be converted into string using the toString() method.

Here are the content of our data.txt file.

File Contents = Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.