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

	try {
	    synchronized (this) {
		return folder.getProtocol().top(msgnum, n);
	    }
	} catch (EOFException eex) {
	    folder.close(false);
	    throw new FolderClosedException(folder, eex.toString());
	} catch (IOException ex) {
	    throw new MessagingException("error getting size", ex);
	}
    }

    /**
     * Get all the headers for this header_name. Note that certain
     * headers may be encoded as per RFC 2047 if they contain 
     * non US-ASCII characters and these should be decoded. <p>
     *
     * @param	name	name of header
     * @return	array of headers
     * @exception       MessagingException
     * @see 	javax.mail.internet.MimeUtility
     */
    public String[] getHeader(String name)
			throws MessagingException {
	if (headers == null)
	    loadHeaders();
	return headers.getHeader(name);
    }

    /**
     * Get all the headers for this header name, returned as a single
     * String, with headers separated by the delimiter. If the
     * delimiter is <code>null</code>, only the first header is 
     * returned.
     *
     * @param name		the name of this header
     * @param delimiter		delimiter between returned headers
     * @return                  the value fields for all headers with 
     *				this name
     * @exception       	MessagingException
     */
    public String getHeader(String name, String delimiter)
				throws MessagingException {
	if (headers == null)
	    loadHeaders();
	return headers.getHeader(name, delimiter);
    }

    /**
     * Set the value for this header_name.  Throws IllegalWriteException
     * because POP3 messages are read-only.
     *
     * @param	name 	header name
     * @param	value	header value
     * @see 	javax.mail.internet.MimeUtility
     * @exception	IllegalWriteException because the underlying
     *			implementation does not support modification
     * @exception	IllegalStateException if this message is
     *			obtained from a READ_ONLY folder.
     */
    public void setHeader(String name, String value)
                                throws MessagingException {
	// XXX - should check for read-only folder?
	throw new IllegalWriteException("POP3 messages are read-only");
    }

    /**
     * Add this value to the existing values for this header_name.
     * Throws IllegalWriteException because POP3 messages are read-only.
     *
     * @param	name 	header name
     * @param	value	header value
     * @see 	javax.mail.internet.MimeUtility
     * @exception	IllegalWriteException because the underlying
     *			implementation does not support modification
     * @exception	IllegalStateException if this message is
     *			obtained from a READ_ONLY folder.
     */
    public void addHeader(String name, String value)
                                throws MessagingException {
	// XXX - should check for read-only folder?
	throw new IllegalWriteException("POP3 messages are read-only");
    }

    /**
     * Remove all headers with this name.
     * Throws IllegalWriteException because POP3 messages are read-only.
     *
     * @exception	IllegalWriteException because the underlying
     *			implementation does not support modification
     * @exception	IllegalStateException if this message is
     *			obtained from a READ_ONLY folder.
     */
    public void removeHeader(String name)
                                throws MessagingException {
	// XXX - should check for read-only folder?
	throw new IllegalWriteException("POP3 messages are read-only");
    }

    /**
     * Return all the headers from this Message as an enumeration
     * of Header objects. <p>
     *
     * Note that certain headers may be encoded as per RFC 2047 
     * if they contain non US-ASCII characters and these should 
     * be decoded. <p>
     *
     * @return	array of header objects
     * @exception  MessagingException
     * @see 	javax.mail.internet.MimeUtility
     */
    public Enumeration getAllHeaders() throws MessagingException {
	if (headers == null)
	    loadHeaders();
	return headers.getAllHeaders();	
    }

    /**
     * Return matching headers from this Message as an Enumeration of
     * Header objects.
     *
     * @exception  MessagingException
     */
    public Enumeration getMatchingHeaders(String[] names)
			throws MessagingException {
	if (headers == null)
	    loadHeaders();
	return headers.getMatchingHeaders(names);
    }

    /**
     * Return non-matching headers from this Message as an
     * Enumeration of Header objects.
     *
     * @exception  MessagingException
     */
    public Enumeration getNonMatchingHeaders(String[] names)
			throws MessagingException {
	if (headers == null)
	    loadHeaders();
	return headers.getNonMatchingHeaders(names);
    }

    /**
     * Add a raw RFC822 header-line. 
     * Throws IllegalWriteException because POP3 messages are read-only.
     *
     * @exception	IllegalWriteException because the underlying
     *			implementation does not support modification
     * @exception	IllegalStateException if this message is
     *			obtained from a READ_ONLY folder.
     */
    public void addHeaderLine(String line) throws MessagingException {
	// XXX - should check for read-only folder?
	throw new IllegalWriteException("POP3 messages are read-only");
    }

    /**
     * Get all header lines as an Enumeration of Strings. A Header
     * line is a raw RFC822 header-line, containing both the "name" 
     * and "value" field. 
     *
     * @exception  	MessagingException
     */
    public Enumeration getAllHeaderLines() throws MessagingException {
	if (headers == null)
	    loadHeaders();
	return headers.getAllHeaderLines();
    }

    /**
     * Get matching header lines as an Enumeration of Strings. 
     * A Header line is a raw RFC822 header-line, containing both 
     * the "name" and "value" field.
     *
     * @exception  	MessagingException
     */
    public Enumeration getMatchingHeaderLines(String[] names)
                                        throws MessagingException {
	if (headers == null)
	    loadHeaders();
	return headers.getMatchingHeaderLines(names);
    }

    /**
     * Get non-matching header lines as an Enumeration of Strings. 
     * A Header line is a raw RFC822 header-line, containing both 
     * the "name" and "value" field.
     *
     * @exception  	MessagingException
     */
    public Enumeration getNonMatchingHeaderLines(String[] names)
                                        throws MessagingException {
	if (headers == null)
	    loadHeaders();
	return headers.getNonMatchingHeaderLines(names);
    }

    /**
     * POP3 message can't be changed.  This method throws
     * IllegalWriteException.
     *
     * @exception	IllegalWriteException because the underlying
     *			implementation does not support modification
     */
    public void saveChanges() throws MessagingException {
	// POP3 Messages are read-only
	throw new IllegalWriteException("POP3 messages are read-only");
    }

    /**
     * Load the headers for this message into the InternetHeaders object.
     * The headers are fetched using the POP3 TOP command.
     */
    private void loadHeaders() throws MessagingException {
	try {
	    synchronized (this) {
		if (headers != null)    // check again under lock
		    return;
		InputStream hdrs = null;
		if (((POP3Store)(folder.getStore())).disableTop ||
			(hdrs = folder.getProtocol().top(msgnum, 0)) == null) {
		    // possibly because the TOP command isn't supported,
		    // load headers as a side effect of loading the entire
		    // content.
		    InputStream cs = getContentStream();
		    cs.close();
		} else {
		    hdrSize = hdrs.available();
		    headers = new InternetHeaders(hdrs);
		}
	    }
	} catch (EOFException eex) {
	    folder.close(false);
	    throw new FolderClosedException(folder, eex.toString());
	} catch (IOException ex) {
	    throw new MessagingException("error loading POP3 headers", ex);
	}
    }
}