Getting mail from GMail into Java application using IMAP

问题

I want to access messages in GMail from a Java application using JavaMail and IMAP. Why am I getting a SocketTimeoutException ?

Here is my code:

Properties props = System.getProperties();
props.setProperty("mail.imap.host", "imap.gmail.com");
props.setProperty("mail.imap.port", "993");
props.setProperty("mail.imap.connectiontimeout", "5000");
props.setProperty("mail.imap.timeout", "5000");

try {
    Session session = Session.getDefaultInstance(props, new MyAuthenticator());
    URLName urlName = new URLName("imap://MYUSERNAME@gmail.com:MYPASSWORD@imap.gmail.com");
    Store store = session.getStore(urlName);
    if (!store.isConnected()) {
        store.connect();
    }
} catch (NoSuchProviderException e) {
    e.printStackTrace();
    System.exit(1);
} catch (MessagingException e) {
    e.printStackTrace();
    System.exit(2);
}

I set the timeout values so that it wouldn't take "forever" to timeout. Also, MyAuthenticator also has the username and password, which seems redundant with the URL. Is there another way to specify the protocol? (I didn't see it in the JavaDoc for IMAP.)

回答1:

Using imaps was a great suggestion. Neither of the answers provided just worked for me, so I googled some more and found something that worked. Here's how my code looks now.

Properties props = System.getProperties();
props.setProperty("mail.store.protocol", "imaps");
try {
  Session session = Session.getDefaultInstance(props, null);
  Store store = session.getStore("imaps");
  store.connect("imap.gmail.com", "<username>@gmail.com", "<password>");
  ...
} catch (NoSuchProviderException e) {
  e.printStackTrace();
  System.exit(1);
} catch (MessagingException e) {
  e.printStackTrace();
  System.exit(2);
}

This is nice because it takes the redundant Authenticator out of the picture. I'm glad this worked because the SSLNOTES.txt make my head spin.

回答2:

You need to use the following properties for imaps:

props.setProperty("mail.imaps.host", "imap.gmail.com");
props.setProperty("mail.imaps.port", "993");
props.setProperty("mail.imaps.connectiontimeout", "5000");
props.setProperty("mail.imaps.timeout", "5000");

Notices it's "imaps", not "imap", since the protocol you're using is imaps (IMAP + SSL)

回答3:

In JavaMail, you can use imaps as the URL scheme to use IMAP over SSL. (See SSLNOTES.txt in your JavaMail distribution for more details.) For example, imaps://username%40gmail.com@imap.gmail.com/INBOX.

Similarly, use smtps to send emails via Gmail. e.g., smtps://username%40gmail.com@smtp.gmail.com/. Again, read SSLNOTES.txt for more details. Hope it helps!

回答4:

You have to connect to GMail using SSL only. Setting the following properties will force that for you.

props.setProperty("mail.imap.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
props.setProperty("mail.imap.socketFactory.fallback", "false");

回答5:

If you'd like more sample code on using JavaMail with Gmail (e.g. converting Gmail labels to IMAP folder names, or using IMAP IDLE), do check out my program GmailAssistant on SourceForge.

回答6:

Here is what worked for my team and I, given a classic account nickname@gmail.com and a business account employee@business.com :

            final Properties properties = new Properties();
            properties.put("mail.imap.ssl.enable", "true");

            imapSession = Session.getInstance(properties, null);
            imapSession.setDebug(false);
            imapStore = imapSession.getStore("imap");

            imapStore.connect("imap.gmail.com", USERNAME, "password");

with USERNAME = "nickname" in the classic case, and USERNAME = "employee@business.com" in the business account case.

In the classic case, and if you use an old JavaMail dependency, don't forget to lower the account security here : https://www.google.com/settings/security/lesssecureapps

In both cases check in GMail Settings => Forwarding POP / IMAP if IMAP is enabled for the account.

Hope it helps!

To go further :

• http://www.oracle.com/technetwork/java/javamail/faq/index.html#gmail
• https://support.google.com/mail/accounts/answer/78754

回答7:

Check http://g4j.sourceforge.net/. There is a minimal gmail client built using this API.

回答8:

I used following properties to get the store and It works well.

"mail.imaps.host" : "imap.gmail.com"
"mail.store.protocol" : "imaps"
"mail.imaps.port" : "993"

回答9:

You need to have JSSE installed to use SSL with Java

回答10:

URLName server = new URLName("imaps://<gmail-user-name>:<gmail-pass>@imap.gmail.com/INBOX");

来源：https://stackoverflow.com/questions/61176/getting-mail-from-gmail-into-java-application-using-imap