在测试 javax.mail 中的 imap 协议 idle 时会有olderClosedException异常。

原因:

在Messaging对象上调用方法并且拥有该对象的Folder由于某种原因而死亡时，将引发此异常。

由于我没注意看文档，IMAPFolder.idle();是阻塞的而又没有循环读，导致直接关闭了资源~

收件箱中共633封邮件!
收件箱中共78封未读邮件!
收件箱中共0封新邮件!
收件箱中共0封已删除邮件!
------------------------开始解析邮件----------------------------------
支持idle
Got 1 new messages
---------------------------------------------------
-----关闭资源-----
标题: Re:测试邮件推送
javax.mail.FolderClosedException
	at com.sun.mail.imap.IMAPMessage.getProtocol(IMAPMessage.java:169)
	at com.sun.mail.imap.IMAPMessage.loadBODYSTRUCTURE(IMAPMessage.java:1546)
	at com.sun.mail.imap.IMAPMessage.getDataHandler(IMAPMessage.java:808)
	at javax.mail.internet.MimeMessage.getContent(MimeMessage.java:1508)
	at io.qyi.qqBotManage.mail.mail$1.messagesAdded(mail.java:88)
	at javax.mail.event.MessageCountEvent.dispatch(MessageCountEvent.java:154)
	at javax.mail.EventQueue.run(EventQueue.java:170)
	at java.lang.Thread.run(Thread.java:745)

import com.sun.mail.imap.IMAPFolder;

import javax.mail.*;
import javax.mail.event.MessageCountAdapter;
import javax.mail.event.MessageCountEvent;
import java.io.IOException;
import java.util.Properties;

/**
 * @author LuoYe
 * @version 1.0
 * @description: TODO
 * @date 2021/5/12 3:13
 */

public class mail {
    public static void main(String[] args) throws MessagingException, IOException {
        init();
    }

    public static void init() throws MessagingException, IOException {
        Properties props = new Properties();
        props.setProperty("mail.store.protocol", "imap");
        props.setProperty("mail.imap.host", "outlook.office365.com");
        props.setProperty("mail.imap.port", "993");
        /*tls与https需要增加以下代码*/
        props.setProperty("mail.imap.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
        props.setProperty("mail.imap.socketFactory.fallback", "false");
        props.setProperty("mail.imap.socketFactory.port", "993");

        Session session = Session.getInstance(props);
        // 创建IMAP协议的Store对象
        Store store = session.getStore("imap");

        // 连接邮件服务器
        store.connect("账户", "密码");

        // 获得收件箱
        Folder folder = store.getFolder("INBOX");
        // 以读写模式打开收件箱
        folder.open(Folder.READ_WRITE);

        // 获得收件箱的邮件列表
        Message[] messages = folder.getMessages();

        // 打印不同状态的邮件数量
        System.out.println("收件箱中共" + messages.length + "封邮件!");
        System.out.println("收件箱中共" + folder.getUnreadMessageCount() + "封未读邮件!");
        System.out.println("收件箱中共" + folder.getNewMessageCount() + "封新邮件!");
        System.out.println("收件箱中共" + folder.getDeletedMessageCount() + "封已删除邮件!");

        System.out.println("------------------------开始解析邮件----------------------------------");

        // 解析邮件
        /*for (Message message : messages) {
            IMAPMessage msg = (IMAPMessage) message;
            String subject = MimeUtility.decodeText(msg.getSubject());
            System.out.println("[" + subject + "]未读，是否需要阅读此邮件（y/n）？");
            BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
            String answer = reader.readLine();
            if ("y".equalsIgnoreCase(answer)) {
                System.out.println(msg.getContent().toString());
                // POP3ReceiveMailTest.parseMessage(msg);	// 解析邮件
                // 第二个参数如果设置为true，则将修改反馈给服务器。false则不反馈给服务器
                // msg.setFlag(Flag.SEEN, true);	//设置已读标志


            }
        }*/

        folder.addMessageCountListener(new MessageCountAdapter() {
            @Override
            public void messagesAdded(MessageCountEvent e) {
                // super.messagesAdded(e);
                Message[] msgs = e.getMessages();
                System.out.println("Got " + msgs.length + " new messages");
                for (Message msg : msgs) {
                    System.out.println("---------------------------------------------------");
                    try {
                        System.out.println("标题: " + msg.getSubject());
                        System.out.println("内容: " + msg.getContent().toString());
                    } catch (MessagingException messagingException) {
                        messagingException.printStackTrace();
                    } catch (IOException ioException) {
                        ioException.printStackTrace();
                    }
                }
            }

            @Override
            public void messagesRemoved(MessageCountEvent e) {
                super.messagesRemoved(e);
            }
        });

        if (folder instanceof IMAPFolder) {
            System.out.println("支持idle");
            IMAPFolder f = (IMAPFolder) folder;
            f.idle();
        }

        System.out.println("-----关闭资源-----");
        // 关闭资源
        folder.close(false);
        store.close();


    }
}