How to use libraries correctly in Netbeans (Java)?

Question

This question is about how to handle libraries in Netbeans, when programming in Java.

I am having a Java project, let's call it ABC. One of its activities is to send an email message. Some of my other Java projects also send email messages, so I decided to create a separate Java project for sending messages. This project is called SendEmail. SendEmail uses external jar files (javax.mail.*). These are included by going to SendEmail's project Properties -> Libraries -> Add JAR. Testing SendEmail works fine: when calling its method sendMail(title, contents) do I receive the email which is sent.

Project ABC uses SendEmail, so I have added this to ABC's library: project Properties -> Libraries -> Add Project. ABC compiles and runs fine until it reaches the point where it wants to send an email: it crashes.

private void informUser(){
//create message title
//create message contents
SendEmail email = new SendEmail();
email.sendMail(title, contents); // <- it crashes here
}

The error information states that it can't find the Authenticator class. This class is in the external jar file which is included in SendEmail's library. I can only avoid this crash from happening by including the external jar files to ABC's library. This is what I did not expect to be necessary. ABC does not use these external jar files, only SendEmail does.

My question: am I doing something wrong? I assumed that ABC is not using these external jar's so they don't need to be in ABC's library.

Answer 1

In your code don`t have the authenticator part. This code only can use gmail email, you can change smtp server options. My code:

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.security.Security;
import java.util.Properties;

import javax.activation.DataHandler;
import javax.activation.DataSource;
import javax.mail.Message;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;


public class GmailSender extends javax.mail.Authenticator {

    private String user;
    private String password;
    private Session session;

    static {
        Security.addProvider(new JSSEProvider());
    }

    public GmailSender(String user, String password) {
        this.user = user;
        this.password = password;

        Properties props = new Properties();
        props.setProperty("mail.transport.protocol", "smtp");
        props.setProperty("mail.smtp.host", "smtp.gmail.com");
        props.put("mail.smtp.starttls.enable", "true");
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.port", "465");
        props.put("mail.smtp.socketFactory.port", "465");
        props.put("mail.smtp.socketFactory.class",
                "javax.net.ssl.SSLSocketFactory");
        props.put("mail.smtp.socketFactory.fallback", "false");
        props.setProperty("mail.smtp.quitwait", "false");

        session = Session.getDefaultInstance(props, this);
    }

    protected PasswordAuthentication getPasswordAuthentication() {
        return new PasswordAuthentication(user, password);
    }

    public synchronized void sendMail(String subject, String body, String sender, String recipients) throws Exception {
        try {
            MimeMessage message = new MimeMessage(session);
            DataHandler handler = new DataHandler(new ByteArrayDataSource(body.getBytes(), "text/plain"));
            message.setSender(new InternetAddress(sender));
            message.setSubject(subject);
            message.setDataHandler(handler);
            if (recipients.indexOf(',') > 0)
                message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(recipients));
            else
                message.setRecipient(Message.RecipientType.TO, new InternetAddress(recipients));
            Transport.send(message);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public class ByteArrayDataSource implements DataSource {
        private byte[] data;
        private String type;

        public ByteArrayDataSource(byte[] data, String type) {
            super();
            this.data = data;
            this.type = type;
        }

        public ByteArrayDataSource(byte[] data) {
            super();
            this.data = data;
        }

        public void setType(String type) {
            this.type = type;
        }

        public String getContentType() {
            if (type == null)
                return "application/octet-stream";
            else
                return type;
        }

        public InputStream getInputStream() throws IOException {
            return new ByteArrayInputStream(data);
        }

        public String getName() {
            return "ByteArrayDataSource";
        }

        public OutputStream getOutputStream() throws IOException {
            throw new IOException("Not Supported");
        }
    }


}

And do you need this class:

import java.security.AccessController;
import java.security.Provider;

public class JSSEProvider extends Provider {
    public JSSEProvider() {
        super("HarmonyJSSE", 1.0, "Harmony JSSE Provider");
        AccessController.doPrivileged(new java.security.PrivilegedAction<Void>() {
            public Void run() {
                put("SSLContext.TLS",
                        "org.apache.harmony.xnet.provider.jsse.SSLContextImpl");
                put("Alg.Alias.SSLContext.TLSv1", "TLS");
                put("KeyManagerFactory.X509",
                        "org.apache.harmony.xnet.provider.jsse.KeyManagerFactoryImpl");
                put("TrustManagerFactory.X509",
                        "org.apache.harmony.xnet.provider.jsse.TrustManagerFactoryImpl");
                return null;
            }
        });
    }
}

For used this code:

class SendEmailTask extends AsyncTask<Void, Void, Void> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
        }

        @Override
        protected Void doInBackground(Void... params) {
            try {
                GmailSender sender = new GmailSender("from email", "from email password");
                //subject, body, sender, to
                StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
                StrictMode.setThreadPolicy(policy);
                sender.sendMail("your title",
                        "your content",
                        "from email",
                        "to email");
            } catch (Exception e) {              
                e.printStackTrace();
            }
            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            super.onPostExecute(result);

        }
    }

and run

SendEmailTask sendEmailTask = new SendEmailTask();
sendEmailTask.execute();

UPD1: Libs: 1. javax.activation 2. javax.mail