Java - POP3 programs

POP3 programs

•       POP3 (Post Office Protocol 3) is the most recent version of a standard protocol for receiving e-mail. POP3 is a client/server protocol in which e-mail is received and held for you by your Internet server.

•         Periodically, client e-mail receiver checks your mail-box on the server and downloads any mail, probably using POP3.

•       This standard protocol is built into most popular e-mail products, such as Eudora and Outlook Express. It's also built into the Netscape and Microsoft Internet Explorer browsers.

•       POP3 is designed to delete mail on the server as soon as the user has downloaded it. However, some implementations allow users or an administrator to specify that mail be saved for some period of time. POP can be thought of as a "store-and-forward" service.

Steps to read a remote mailbox

•       Set up the properties use for the connection.

•       Construct the Authenticator use for the connection.

•       Get a Session object with Session.getDefaultInstance( ).

•       Use the session's getStore( ) method to return a Store.

•       Connect to the store.

•       Get the INBOX folder from the store with the getFolder( ) method.

•       Open the INBOX folder.

•       Open the folder inside the INBOX folder. Repeat as many times as necessary to reach the folder you're seeking.

•       Get the messages from the folder as an array of Message objects.

•       IterateMessageothervitalthroughclassinformation.Fortheinstance,arrayofGUImessages,printforoutthe achprocessingusermessagtoselectachor.simplyoneindisplayturnusingthe sender,themethodssubject,of andth

•       Close the folder.

•       Close the store.

Example

A program that downloads and prints out the contents of a specified POP mailbox. Messages are simply dumped on System.out in the default encoding. The servers, usernames, and so forth are all hard coded.

import javax.mail.*;

import javax.mail.internet.*; import java.util.*;

import java.io.*;

public class POP3Client {

public static void main(String[] args) { Properties props = new Properties( ); String host = "utopia.poly.edu"; String username = "myuser";

String password = "mypwd"; String provider = "pop3"; try {

// Connect to the POP3 server

Session session = Session.getDefaultInstance(props, null); Store store = session.getStore(provider); store.connect(host, username, password);

// Open the folder

Folder inbox = store.getFolder("INBOX"); if (inbox == null) {

System.out.println("No INBOX"); System.exit(1);

}

inbox.open(Folder.READ_ONLY);

// Get the messages from the server Message[] messages = inbox.getMessages( ); for (int i = 0; i < messages.length; i++) {

System.out.println("------- Message " + (i+1) + " ---------

"); messages[i].writeTo(System.out);

}

//  Close the connection

//  but don't remove the messages from the server inbox.close(false);

store.close( );

}

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

}

}

•       The first is to set up the properties for the mail session. Properties you might want to set include mail.host, mail.store.protocol, mail.user, mail.pop3.user, and mail.pop3.host. However, you don't absolutely need to set any of these. If the Session will be used only to retrieve mail, then an empty Properties object will be enough.

•       To create an instance of the javax.mail.Authenticator class (more properly, an instance of a concrete subclass of the abstract Authenticator class) that can ask the user for her password. For now, we'll simply hardcode those values and pass null instead of an actual Authenticator.

•       Use Properties and Authenticator objects to get a Session instance.

•       Now the store is connected and ready to open a folder in the store.

•       The Message class provides many methods for working with individual messages. It has methods to get the various header fields of the message, to get the content of the message, to reply to the message, and more. Now print each message on System.out using the message's writeTo( ) method: