MailSender.java

package io.robe.mail;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.activation.DataHandler;
import javax.activation.DataSource;
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.Map;
import java.util.Properties;

import static com.google.common.base.Preconditions.checkNotNull;


/**
 * A mail sender class.
 */
class MailSender {

    private static final Logger LOGGER = LoggerFactory.getLogger(MailSender.class);
    private static final Properties PROPERTIES = new Properties();
    private final MailConfiguration configuration;
    private Session session;

    /**
     * @param configuration mail configuration
     */
    public MailSender(MailConfiguration configuration) {
        checkNotNull(configuration);
        this.configuration = configuration;
        setProperties();
    }

    public MailConfiguration getConfiguration() {
        return configuration;
    }

    private void setProperties() {
        LOGGER.debug("Setting configuration.");
        LOGGER.debug(configuration.toString());

        PROPERTIES.putAll(configuration.getProperties());


        session = Session.getDefaultInstance(PROPERTIES, new javax.mail.Authenticator() {
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication(
                        PROPERTIES.get(configuration.getUsernameKey()).toString()
                        , PROPERTIES.get(configuration.getPasswordKey()).toString());
            }
        });
    }


    /**
     * Sends a mail with the given item.
     *
     * @param item MailItem to be send.
     */
    public void sendMessage(MailItem item) throws MessagingException {
        checkNotNull(item.getReceivers());
        checkNotNull(item.getReceivers().get(0));
        checkNotNull(item.getTitle());
        checkNotNull(item.getBody());

        //If sender is empty send with the account sender.
        Message msg = new MimeMessage(session);
        if (item.getSender() == null || item.getSender().length() == 0) {
            item.setSender(configuration.getProperties().get(configuration.getUsernameKey()).toString());
        }
        InternetAddress from = new InternetAddress(item.getSender());
        msg.setFrom(from);


        InternetAddress[] to = new InternetAddress[item.getReceivers().size()];
        for (int i = 0; i < item.getReceivers().size(); i++) {
            to[i] = new InternetAddress(item.getReceivers().get(i));
        }
        msg.setRecipients(Message.RecipientType.TO, to);

        msg.setSubject(item.getTitle());

        MimeBodyPart body = new MimeBodyPart();
        body.setContent(item.getBody(), "text/html; charset=UTF-8");
        Multipart content = new MimeMultipart();
        content.addBodyPart(body);

        if (item.getAttachments() != null && item.getAttachments().size() > 0) {
            for (DataSource attachment : item.getAttachments()) {
                BodyPart itemBodyPart = new MimeBodyPart();
                itemBodyPart.setDataHandler(new DataHandler(attachment));
                itemBodyPart.setFileName(attachment.getName());
                content.addBodyPart(itemBodyPart);
            }
        }

        msg.setContent(content);

        //update headers
        msg.saveChanges();

        Transport.send(msg);

        // set header value
        for (Map.Entry<String, String[]> entry : item.getHeaders().entrySet()) {
            String[] value = msg.getHeader(entry.getKey());
            if (value != null) {
                entry.setValue(value);
            }
        }

    }


}