简单的收信的例子：SimpleReceiver

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--- 简单的收信的例子：SimpleReceiver (http://www.webasp.net/article/8/7055.htm)
-- 作者：未知
-- 发布日期： 2003-07-26
import javax.mail.*;
import javax.mail.internet.*;
import java.util.*;
import java.io.*;

/**
* A simple email receiver class.
*/
public class SimpleReceiver{
/**
　* Main method to receive messages from the mail server specified
　* as command line arguments.
　*/
    public static void main(String args[]){
        try{
            String popServer=args[0];
            String popUser=args[1];
            String popPassword=args[2];
            receive(popServer, popUser, popPassword);
        }catch (Exception ex){
            System.out.println("Usage: java com.lotontech.mail.SimpleReceiver"+" popServer popUser popPassword");
        }
        System.exit(0);
    }
    /**
    * "receive" method to fetch messages and process them.
    */
    public static void receive(String popServer, String popUser, String popPassword){
        Store store=null;
        Folder folder=null;
        try{
            // -- Get hold of the default session --
            Properties props = System.getProperties();
            Session session = Session.getDefaultInstance(props, null);
            // -- Get hold of a POP3 message store, and connect to it --
            store = session.getStore("pop3");
            store.connect(popServer, popUser, popPassword);
            // -- Try to get hold of the default folder --
            folder = store.getDefaultFolder();
            if (folder == null) throw new Exception("No default folder");
            // -- ...and its INBOX --
            folder = folder.getFolder("INBOX");
            if (folder == null) throw new Exception("No POP3 INBOX");
            // -- Open the folder for read only --
            folder.open(Folder.READ_ONLY);
            // -- Get the message wrappers and process them --
            Message[] msgs = folder.getMessages();
            for (int msgNum = 0; msgNum < msgs.length; msgNum++){
                printMessage(msgs[msgNum]);
            }
        }catch (Exception ex){
            ex.printStackTrace();
        }
        finally{
        // -- Close down nicely --
            try{
                if (folder!=null) folder.close(false);
                if (store!=null) store.close();
            }catch (Exception ex2) {
                ex2.printStackTrace();
            }
        }
    }
    /**
    * "printMessage()" method to print a message.
    */
    public static void printMessage(Message message){
        try{
            // Get the header information
            String from=((InternetAddress)message.getFrom()[0]).getPersonal();
            if (from==null) from=((InternetAddress)message.getFrom()[0]).getAddress();
            System.out.println("FROM: "+from);
            String subject=message.getSubject();
            System.out.println("SUBJECT: "+subject);
            // -- Get the message part (i.e. the message itself) --
            Part messagePart=message;
            Object content=messagePart.getContent();
            // -- or its first body part if it is a multipart message --
            if (content instanceof Multipart){
                messagePart=((Multipart)content).getBodyPart(0);
                System.out.println("[ Multipart Message ]");
            }
            // -- Get the content type --
            String contentType=messagePart.getContentType();
            // -- If the content is plain text, we can print it --
            System.out.println("CONTENT:"+contentType);
            if (contentType.startsWith("text/plain")||
                contentType.startsWith("text/html")){
                InputStream is = messagePart.getInputStream();
                BufferedReader reader=new BufferedReader(new InputStreamReader(is));
                String thisLine=reader.readLine();
                while (thisLine!=null){
                    System.out.println(thisLine);
                    thisLine=reader.readLine();
                }
            }
            System.out.println("-----------------------------");
        }catch (Exception ex){
            ex.printStackTrace();
        }
    }
}
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