pop3message.java

此源码是在sun站点上提供的javamail基础上改进。用来解决中文邮件或很多国际间邮件乱码问题。版权属于sun公司。不过当你开发webmail程序时做邮件展示时

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/*
 * @(#)POP3Message.java	1.18 07/05/04
 */

package com.sun.mail.pop3;

import java.io.*;
import java.util.Enumeration;
import javax.mail.*;
import javax.mail.internet.*;
import javax.mail.event.*;

/**
 * A POP3 Message.  Just like a MimeMessage except that
 * some things are not supported.
 *
 * @author      Bill Shannon
 */
public class POP3Message extends MimeMessage {

    /*
     * Our locking strategy is to always lock the POP3Folder before the
     * POP3Message so we have to be careful to drop our lock before calling
     * back to the folder to close it and notify of connection lost events.
     */

    // flag to indicate we haven't tried to fetch the UID yet
    static final String UNKNOWN = "UNKNOWN";

    private POP3Folder folder;	// overrides folder in MimeMessage
    private int hdrSize = -1;
    private int msgSize = -1;
    String uid = UNKNOWN;	// controlled by folder lock

    public POP3Message(Folder folder, int msgno)
			throws MessagingException {
	super(folder, msgno);
	this.folder = (POP3Folder)folder;
    }

    /**
     * Set the specified flags on this message to the specified value.
     *
     * @param newFlags	the flags to be set
     * @param set	the value to be set
     */
    public void setFlags(Flags newFlags, boolean set)
				throws MessagingException {
	Flags oldFlags = (Flags)flags.clone();
	super.setFlags(newFlags, set);
	if (!flags.equals(oldFlags))
	    folder.notifyMessageChangedListeners(
				MessageChangedEvent.FLAGS_CHANGED, this);
    }

    /**
     * Return the size of the content of this message in bytes. 
     * Returns -1 if the size cannot be determined. <p>
     *
     * Note that this number may not be an exact measure of the
     * content size and may or may not account for any transfer
     * encoding of the content. <p>
     *
     * @return          size of content in bytes
     * @exception	MessagingException
     */  
    public int getSize() throws MessagingException {
	try {
	    synchronized (this) {
		if (msgSize >= 0)
		    return msgSize;
		if (msgSize < 0) {
		    /*
		     * Use LIST to determine the entire message
		     * size and subtract out the header size
		     * (which may involve loading the headers,
		     * which may load the content as a side effect).
		     * If the content is loaded as a side effect of
		     * loading the headers, get the size directly.
		     */
		    if (headers == null)
			loadHeaders();
		    if (contentStream != null)
			msgSize = contentStream.available();
		    else
			msgSize = folder.getProtocol().list(msgnum) - hdrSize;
		}
		return msgSize;
	    }
	} catch (EOFException eex) {
	    folder.close(false);
	    throw new FolderClosedException(folder, eex.toString());
	} catch (IOException ex) {
	    throw new MessagingException("error getting size", ex);
	}
    }

    /**
     * Produce the raw bytes of the content.  The data is fetched using
     * the POP3 RETR command.
     *
     * @see #contentStream
     */
    protected InputStream getContentStream()
					throws MessagingException {
	try {
	synchronized(this) {
	    if (contentStream == null) {
		InputStream rawcontent = folder.getProtocol().retr(msgnum,
					msgSize > 0 ? msgSize + hdrSize : 0);
		if (rawcontent == null) {
		    expunged = true;
		    throw new MessageRemovedException();    //  XXX - what else?
		}
		if (headers == null ||
			((POP3Store)(folder.getStore())).forgetTopHeaders) {
		    headers = new InternetHeaders(rawcontent);
		    hdrSize =
			(int)((SharedInputStream)rawcontent).getPosition();
		} else {
		    /*
		     * Already have the headers, have to skip the headers
		     * in the content array and return the body.
		     *
		     * XXX - It seems that some mail servers return slightly
		     * different headers in the RETR results than were returned
		     * in the TOP results, so we can't depend on remembering
		     * the size of the headers from the TOP command and just
		     * skipping that many bytes.  Instead, we have to process
		     * the content, skipping over the header until we come to
		     * the empty line that separates the header from the body.
		     */
		    int offset = 0;
		    for (;;) {
			int len = 0;	// number of bytes in this line
			int c1;
			while ((c1 = rawcontent.read()) >= 0) {
			    if (c1 == '\n')	// end of line
				break;
			    else if (c1 == '\r') {
				// got CR, is the next char LF?
				if (rawcontent.available() > 0) {
				    rawcontent.mark(1);
				    if (rawcontent.read() != '\n')
					rawcontent.reset();
				}
				break;	// in any case, end of line
			    }

			    // not CR, NL, or CRLF, count the byte
			    len++;
			}
			// here when end of line or out of data

			// if out of data, we're done
			if (rawcontent.available() == 0)
			    break;
			
			// if it was an empty line, we're done
			if (len == 0)
			    break;
		    }
		    hdrSize =
			(int)((SharedInputStream)rawcontent).getPosition();
		}
		contentStream =
		    ((SharedInputStream)rawcontent).newStream(hdrSize, -1);
		rawcontent = null;	// help GC
	    }
	}
	} catch (EOFException eex) {
	    folder.close(false);
	    throw new FolderClosedException(folder, eex.toString());
	} catch (IOException ex) {
	    throw new MessagingException("error fetching POP3 content", ex);
	}
	return super.getContentStream();
    }

    /**
     * Invalidate the cache of content for this message object, causing 
     * it to be fetched again from the server the next time it is needed.
     * If <code>invalidateHeaders</code> is true, invalidate the headers
     * as well.
     *
     * @param	invalidateHeaders	invalidate the headers as well?
     */
    public synchronized void invalidate(boolean invalidateHeaders) {
	content = null;
	contentStream = null;
	msgSize = -1;
	if (invalidateHeaders) {
	    headers = null;
	    hdrSize = -1;
	}
    }

    /**
     * Fetch the header of the message and the first <code>n</code> lines
     * of the raw content of the message.  The headers and data are
     * available in the returned InputStream.
     *
     * @param	n	number of lines of content to fetch
     * @return	InputStream containing the message headers and n content lines
     */
    public InputStream top(int n) throws MessagingException {