Question

Problem with Session.getInstance(props, null);

Posted on September 9, 2024
Slovak and Czech language
Asked by f88e4992517d4bf4a4c57a9265b817

Execuse me, if I can use your sample for send mail, but line Session session = Session.getInstance(props, null); ended with error: java.lang.NoClassDefFoundError: javax.mail.Session and Cound not find method javax.mail.Session.getInstance.

Can you help me?

Pavel Kosulic / pavl.kosulic@rts.cz Thank you.

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Bobby Iliev

Site Moderator

• September 9, 2024

Accepted Answer

Hi there,

The error java.lang.NoClassDefFoundError: javax.mail.Session typically indicates that the JavaMail API (which includes the Session class) is not properly included in your project’s classpath.

If you are using Maven for your project, you need to include the JavaMail dependency in your pom.xml file:

<dependency>
    <groupId>com.sun.mail</groupId>
    <artifactId>javax.mail</artifactId>
    <version>1.6.2</version>
</dependency>

If you’re using Gradle, add this line to your build.gradle file:

implementation 'com.sun.mail:javax.mail:1.6.2'

For other build tools or if you’re managing dependencies manually, make sure the javax.mail.jar file is included in your classpath.

If you’re not using a build tool like Maven or Gradle, you can download the JavaMail API manually:

Go to the JavaMail project page and download the javax.mail.jar.
Add the javax.mail.jar file to your project’s classpath.

If you’re using a recent version of Java (e.g., Java 11 or newer), note that Java EE modules like javax.mail were removed from the JDK. You must explicitly add these dependencies to your project, as mentioned above.

Once you’ve added the JavaMail API to your project, your code should work correctly:

import javax.mail.Session;
import java.util.Properties;

public class SendEmail {
    public static void main(String[] args) {
        Properties props = new Properties();
        props.put("mail.smtp.host", "smtp.example.com");
        props.put("mail.smtp.port", "587");

        Session session = Session.getInstance(props, null);

        // Your email sending logic here
    }
}

If you continue to face issues, double-check that the correct version of the JavaMail API is included and that your IDE or build tool is correctly configured to include it in the classpath.

Hope that this helps!

- Bobby

KFSys

Site Moderator

• September 11, 2024

Add the JavaMail (or Jakarta Mail) dependency:

Depending on your project setup, you will need to include the JavaMail API in your project.

If you’re using Maven, add the following dependency to your pom.xml:

<dependency>
    <groupId>com.sun.mail</groupId>
    <artifactId>javax.mail</artifactId>
    <version>1.6.2</version>
</dependency>

Alternatively, if you’re using the latest Jakarta Mail, use this:

<dependency>
    <groupId>jakarta.mail</groupId>
    <artifactId>jakarta.mail-api</artifactId>
    <version>2.0.1</version>
</dependency>

Sample JavaMail Code:

Here’s an example of how to send an email using the JavaMail API:

import java.util.Properties;
import javax.mail.Message;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

public class MailSender {
    public static void main(String[] args) {
        // Set up the properties for the mail server (SMTP server)
        Properties props = new Properties();
        props.put("mail.smtp.host", "smtp.example.com");
        props.put("mail.smtp.port", "587");
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.starttls.enable", "true");

        // Get a new Session instance
        Session session = Session.getInstance(props, null);

        try {
            // Create a new email message
            MimeMessage message = new MimeMessage(session);
            message.setFrom(new InternetAddress("from@example.com"));
            message.addRecipient(Message.RecipientType.TO, new InternetAddress("to@example.com"));
            message.setSubject("Test Mail");
            message.setText("This is a test email.");

            // Send the message
            Transport.send(message);
            System.out.println("Email sent successfully.");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Make sure the correct JavaMail or Jakarta Mail dependency is included in your project.
Ensure that you have configured the classpath correctly for your environment.