使用 IMAP（javamail API）从 gmail 访问电子邮件

Question

我正在尝试借助 JavaMail API 通过 IMAP 访问来自 Gmail 帐户的电子邮件。我想知道为什么该代码适用于一个电子邮件帐户但不适用于另一个。

我可以访问两个电子邮件帐户的Inbox 文件夹。但是对于其中一个电子邮件帐户，无法访问其他文件夹（如 SPAM([Gmail]/Spam)）并引发 FolderNotFoundException 异常。有人可以解释发生了什么问题吗？

提前谢谢你。

代码如下：

import java.io.*;
import java.util.*;
import javax.mail.*;
import javax.mail.Flags.Flag;
import javax.mail.internet.*;

import com.sun.mail.imap.IMAPFolder;
import com.sun.mail.imap.IMAPMessage;


public class FolderFetchIMAP {


    public static void main(String[] args) throws MessagingException, IOException {
        IMAPFolder folder = null;
        Store store = null;
        String subject = null;
        Flag flag = null;
        try 
        {
          Properties props = System.getProperties();
          props.setProperty("mail.store.protocol", "imaps");

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

          store = session.getStore("imaps");
          store.connect("imap.googlemail.com","myemailid@gmail.com", "password");

          folder = (IMAPFolder) store.getFolder("[Gmail]/Spam"); // This doesn't work for other email account
          //folder = (IMAPFolder) store.getFolder("inbox"); This works for both email account


          if(!folder.isOpen())
          folder.open(Folder.READ_WRITE);
          Message[] messages = folder.getMessages();
          System.out.println("No of Messages : " + folder.getMessageCount());
          System.out.println("No of Unread Messages : " + folder.getUnreadMessageCount());
          System.out.println(messages.length);
          for (int i=0; i < messages.length;i++) 
          {

            System.out.println("*****************************************************************************");
            System.out.println("MESSAGE " + (i + 1) + ":");
            Message msg =  messages[i];
            //System.out.println(msg.getMessageNumber());
            //Object String;
            //System.out.println(folder.getUID(msg)

            subject = msg.getSubject();

            System.out.println("Subject: " + subject);
            System.out.println("From: " + msg.getFrom()[0]);
           System.out.println("To: "+msg.getAllRecipients()[0]);
            System.out.println("Date: "+msg.getReceivedDate());
            System.out.println("Size: "+msg.getSize());
            System.out.println(msg.getFlags());
            System.out.println("Body: \n"+ msg.getContent());
            System.out.println(msg.getContentType());

          }
        }
        finally 
        {
          if (folder != null && folder.isOpen()) { folder.close(true); }
          if (store != null) { store.close(); }
        }

    }



}

Answer 1

它是这样工作的（看起来它不适用于 POP3，但它适用于 IMAP）：

     Properties props = new Properties();
     props.put("mail.store.protocol", "imaps");
     Session session = Session.getDefaultInstance(props, null);
     Store store = session.getStore("imaps");
     store.connect("imap.gmail.com", [theMailAccount@gmail.com], [thePasswordOrAppPassword]);

     // You possibly will have to use [Google Mail]/All Mail instead
     Folder inbox = store.getFolder("[Gmail]/All Mail");

Answer 2

你可以试试下面的代码：

private List<String> getResult1(){
  try {
    Properties props = new Properties();
    props.put("mail.store.protocol","imaps");
    Session session = Session.getDefaultInstance(props, null);
    Store store = session.getStore("imaps");
    store.connect("imap.gmail.com", "Email Id", "App Password");

    //if you want mail from specified folder, just change change folder name
    //Folder inbox = store.getFolder("[Gmail]/Drafts");
    Folder inbox = store.getFolder("inbox");

    inbox.open(Folder.READ_ONLY);
    int messageCount = inbox.getMessageCount();
    Log.e("getFolder ", "getResult1: " + store.getDefaultFolder().list("*"));
    javax.mail.Folder[] folders = store.getDefaultFolder().list("*");

    for (javax.mail.Folder folder : folders) {
      if ((folder.getType() & javax.mail.Folder.HOLDS_MESSAGES) != 0){
        Log.e("getFolder ", "getResult1: " + folder.getName() );
      }
    }

    Log.e("Mail Subject:", "Total Messages:-: " + messageCount );
    javax.mail.Message[] messages = inbox.getMessages();

    System.out.println("------------------------------");
    Log.e("Mail Subject:", "messages: " + messages.toString());
    for (int i = 0; i < messages.length; i++) {
      Log.e("Mail Subject:", "getResult1: " + messages[i].getSubject());
    }
    inbox.close(true);
    store.close();
  } catch (Exception e) {
    e.printStackTrace();
  }
  return null;
}

Answer 3

package com.technicalkeeda;

import java.io.File;
import java.io.FileInputStream;
import java.util.Properties;

import javax.mail.Folder;
import javax.mail.Message;
import javax.mail.Session;
import javax.mail.Store;

public class GmailInbox {

 public static void main(String[] args) {
  GmailInbox gmail = new GmailInbox();
  gmail.read();
 }

 public void read() {
  Properties props = new Properties();
  try {
   props.load(new FileInputStream(new File("C:\\smtp.properties")));
   Session session = Session.getDefaultInstance(props, null);

   Store store = session.getStore("imaps");
   store.connect("smtp.gmail.com", "*************@gmail.com","your_password");

   Folder inbox = store.getFolder("inbox");
   inbox.open(Folder.READ_ONLY);
   int messageCount = inbox.getMessageCount();

   System.out.println("Total Messages:- " + messageCount);

   Message[] messages = inbox.getMessages();
   System.out.println("------------------------------");
   for (int i = 0; i < 10; i++) {
      System.out.println("Mail Subject:- " + messages[i].getSubject());      
   }
   inbox.close(true);
   store.close();

  } catch (Exception e) {
   e.printStackTrace();
  }
 }

}

Answer 4

其中一个帐户是否有任何机会使用非英语用户界面？

Gmail 文件夹名称已根据用户本地化设置进行本地化。

目前获取本地化文件夹名称的唯一方法是使用 XLIST 命令。

Answer 5

我不确定这是否有帮助，但我已经看到 gmail 帐户具有不同邮箱的情况，即..

Gmail 帐户 1：-

[[Google Mail]]
[[Google Mail]/All Mail]
[[Google Mail]/Bin]
[[Google Mail]/Drafts]
[[Google Mail]/Important]
[[Google Mail]/Sent Mail]
[[Google Mail]/Spam]
[[Google Mail]/Starred]

Gmail 帐户 2：-

[[Gmail]]
[[Gmail]/All Mail]
[[Gmail]/Bin]
[[Gmail]/Drafts]
[[Gmail]/Important]
[[Gmail]/Sent Mail]
[[Gmail]/Spam]
[[Gmail]/Starred]