Download all e-mails in a specific folder into a single text file. Specific for Google Apps accounts.

Main.java

package com.kentcdodds.gmailretriever.main;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Date;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Properties;
import java.util.Set;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.mail.*;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMultipart;

/**
 *
 * @author kentdodds
 */
public class Main {

  private Store store;
  private String username = "[email protected]",
          password = "PASSWORD",
          folderName = "FOLDER NAME",
          outputFile = System.getProperty("user.home") + "/Desktop/" + folderName + ".txt",
          nl = System.getProperty("line.separator");
  private int limit = -1;

  /**
   * @param args the command line arguments
   */
  public static void main(String[] args) throws MessagingException, IOException {
    Main m = new Main();
    m.connectToGoogle();
    m.printFolderContents();
  }

  private void connectToGoogle() throws MessagingException {
    Properties props = System.getProperties();
    props.setProperty("mail.store.protocol", "imaps");
    Session session = Session.getDefaultInstance(props, null);
    store = session.getStore("imaps");
    store.connect("imap.gmail.com", username, password);
  }

  private void printFolderContents() throws MessagingException, IOException {
    Folder folder = store.getFolder(folderName);
    folder.open(Folder.READ_ONLY);
    Message[] messages = folder.getMessages();
    File file = new File(outputFile);
    System.out.println(file.getPath());
    if (!file.exists()) {
      file.createNewFile();
    }

    PrintWriter pw = new PrintWriter(file);
    for (int i = 0; i < messages.length && (i < limit || limit < 0); i++) {
      Message message = messages[i];
      try {
        String body = getMessageBody(message);
        if (body == null) {
          System.err.println("Null body with message: " + getMessageInfo(message));
        } else {
          System.out.println("Printing " + message.getSubject());
          pw.println(getMessageInfo(message));
          pw.println(nl + nl);
          pw.println("-----------------------------------------------------------------------------");
          pw.println(nl + nl);
        }
      } catch (IOException ex) {
        Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
      }
    }
    folder.close(false);
    pw.close();
  }

  private String getMessageBody(Message message) throws MessagingException, IOException {
    String type = message.getContentType();
    String body = null;
    if (type.contains("TEXT/PLAIN")) {
      return (String) message.getContent();
    }

    if (type.contains("multipart")) {
      MimeMultipart multipart = (MimeMultipart) message.getContent();
      for (int i = 0; i < multipart.getCount(); i++) {
        BodyPart bodyPart = multipart.getBodyPart(i);
        String contentType = bodyPart.getContentType();
        if (contentType.contains("TEXT/PLAIN")) {
          return (String) bodyPart.getContent();
        } else if (contentType.contains("TEXT/HTML")) {
          body = (String) bodyPart.getContent();
        }
      }
    }
    return body;
  }

  private String getMessageInfo(Message message) throws MessagingException, IOException {

    return "Subject: " + message.getSubject() + nl
            + "Date: " + message.getSentDate() + nl
            + "From: " + getAddressAsString(message.getFrom()) + nl
            + "To: " + getAddressAsString(message.getRecipients(Message.RecipientType.TO)) + nl
            + "Cc: " + getAddressAsString(message.getRecipients(Message.RecipientType.CC)) + nl
            + "Bcc: " + getAddressAsString(message.getRecipients(Message.RecipientType.BCC)) + nl
            + "Body:" + nl + nl
            + getMessageBody(message);
  }

  private String getAddressAsString(Address... addresses) {
    if (addresses == null) {
      return "";
    }
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < addresses.length; i++) {
      if (i > 0) {
        sb.append(", ");
      }
      sb.append(addresses[i]);
    }
    return sb.toString();
  }
}