/*
* Copyright (c) 1997, 2018 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0, which is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
package org.jvnet.mimepull;
import java.io.*;
This is a utility class that provides various MIME related
functionality.
There are a set of methods to encode and decode MIME headers as
per RFC 2047. Note that, in general, these methods are
not needed when using methods such as
setSubject and setRecipients; JavaMail
will automatically encode and decode data when using these "higher
level" methods. The methods below are only needed when maniuplating
raw MIME headers using setHeader and getHeader
methods. A brief description on handling such headers is given below:
RFC 822 mail headers must contain only US-ASCII
characters. Headers that contain non US-ASCII characters must be
encoded so that they contain only US-ASCII characters. Basically,
this process involves using either BASE64 or QP to encode certain
characters. RFC 2047 describes this in detail.
In Java, Strings contain (16 bit) Unicode characters. ASCII is a
subset of Unicode (and occupies the range 0 - 127). A String
that contains only ASCII characters is already mail-safe. If the
String contains non US-ASCII characters, it must be encoded. An
additional complexity in this step is that since Unicode is not
yet a widely used charset, one might want to first charset-encode
the String into another charset and then do the transfer-encoding.
Note that to get the actual bytes of a mail-safe String (say,
for sending over SMTP), one must do
byte[] bytes = string.getBytes("iso-8859-1");
The setHeader and addHeader methods
on MimeMessage and MimeBodyPart assume that the given header values
are Unicode strings that contain only US-ASCII characters. Hence
the callers of those methods must insure that the values they pass
do not contain non US-ASCII characters. The methods in this class
help do this.
The getHeader family of methods on MimeMessage and
MimeBodyPart return the raw header value. These might be encoded
as per RFC 2047, and if so, must be decoded into Unicode Strings.
The methods in this class help to do this.
Several System properties control strict conformance to the MIME
spec. Note that these are not session properties but must be set
globally as System properties.
The mail.mime.decodetext.strict property controls
decoding of MIME encoded words. The MIME spec requires that encoded
words start at the beginning of a whitespace separated word. Some
mailers incorrectly include encoded words in the middle of a word.
If the mail.mime.decodetext.strict System property is
set to "false", an attempt will be made to decode these
illegal encoded words. The default is true.
The mail.mime.encodeeol.strict property controls the
choice of Content-Transfer-Encoding for MIME parts that are not of
type "text". Often such parts will contain textual data for which
an encoding that allows normal end of line conventions is appropriate.
In rare cases, such a part will appear to contain entirely textual
data, but will require an encoding that preserves CR and LF characters
without change. If the mail.mime.encodeeol.strict
System property is set to "true", such an encoding will
be used when necessary. The default is false.
In addition, the mail.mime.charset System property can
be used to specify the default MIME charset to use for encoded words
and text parts that don't otherwise specify a charset. Normally, the
default MIME charset is derived from the default Java charset, as
specified in the file.encoding System property. Most
applications will have no need to explicitly set the default MIME
charset. In cases where the default MIME charset to be used for
mail messages is different than the charset used for files stored on
the system, this property should be set.
The current implementation also supports the following System property.
The mail.mime.ignoreunknownencoding property controls
whether unknown values in the Content-Transfer-Encoding
header, as passed to the decode method, cause an exception.
If set to "true", unknown values are ignored and 8bit
encoding is assumed. Otherwise, unknown values cause a MessagingException
to be thrown.
Author: John Mani, Bill Shannon
/**
* This is a utility class that provides various MIME related
* functionality. <p>
*
* There are a set of methods to encode and decode MIME headers as
* per RFC 2047. Note that, in general, these methods are
* <strong>not</strong> needed when using methods such as
* <code>setSubject</code> and <code>setRecipients</code>; JavaMail
* will automatically encode and decode data when using these "higher
* level" methods. The methods below are only needed when maniuplating
* raw MIME headers using <code>setHeader</code> and <code>getHeader</code>
* methods. A brief description on handling such headers is given below: <p>
*
* RFC 822 mail headers <strong>must</strong> contain only US-ASCII
* characters. Headers that contain non US-ASCII characters must be
* encoded so that they contain only US-ASCII characters. Basically,
* this process involves using either BASE64 or QP to encode certain
* characters. RFC 2047 describes this in detail. <p>
*
* In Java, Strings contain (16 bit) Unicode characters. ASCII is a
* subset of Unicode (and occupies the range 0 - 127). A String
* that contains only ASCII characters is already mail-safe. If the
* String contains non US-ASCII characters, it must be encoded. An
* additional complexity in this step is that since Unicode is not
* yet a widely used charset, one might want to first charset-encode
* the String into another charset and then do the transfer-encoding.
* <p>
* Note that to get the actual bytes of a mail-safe String (say,
* for sending over SMTP), one must do
* <p><blockquote><pre>
*
* byte[] bytes = string.getBytes("iso-8859-1");
*
* </pre></blockquote><p>
*
* The <code>setHeader</code> and <code>addHeader</code> methods
* on MimeMessage and MimeBodyPart assume that the given header values
* are Unicode strings that contain only US-ASCII characters. Hence
* the callers of those methods must insure that the values they pass
* do not contain non US-ASCII characters. The methods in this class
* help do this. <p>
*
* The <code>getHeader</code> family of methods on MimeMessage and
* MimeBodyPart return the raw header value. These might be encoded
* as per RFC 2047, and if so, must be decoded into Unicode Strings.
* The methods in this class help to do this. <p>
*
* Several System properties control strict conformance to the MIME
* spec. Note that these are not session properties but must be set
* globally as System properties. <p>
*
* The <code>mail.mime.decodetext.strict</code> property controls
* decoding of MIME encoded words. The MIME spec requires that encoded
* words start at the beginning of a whitespace separated word. Some
* mailers incorrectly include encoded words in the middle of a word.
* If the <code>mail.mime.decodetext.strict</code> System property is
* set to <code>"false"</code>, an attempt will be made to decode these
* illegal encoded words. The default is true. <p>
*
* The <code>mail.mime.encodeeol.strict</code> property controls the
* choice of Content-Transfer-Encoding for MIME parts that are not of
* type "text". Often such parts will contain textual data for which
* an encoding that allows normal end of line conventions is appropriate.
* In rare cases, such a part will appear to contain entirely textual
* data, but will require an encoding that preserves CR and LF characters
* without change. If the <code>mail.mime.encodeeol.strict</code>
* System property is set to <code>"true"</code>, such an encoding will
* be used when necessary. The default is false. <p>
*
* In addition, the <code>mail.mime.charset</code> System property can
* be used to specify the default MIME charset to use for encoded words
* and text parts that don't otherwise specify a charset. Normally, the
* default MIME charset is derived from the default Java charset, as
* specified in the <code>file.encoding</code> System property. Most
* applications will have no need to explicitly set the default MIME
* charset. In cases where the default MIME charset to be used for
* mail messages is different than the charset used for files stored on
* the system, this property should be set. <p>
*
* The current implementation also supports the following System property.
* <p>
* The <code>mail.mime.ignoreunknownencoding</code> property controls
* whether unknown values in the <code>Content-Transfer-Encoding</code>
* header, as passed to the <code>decode</code> method, cause an exception.
* If set to <code>"true"</code>, unknown values are ignored and 8bit
* encoding is assumed. Otherwise, unknown values cause a MessagingException
* to be thrown.
*
* @author John Mani
* @author Bill Shannon
*/
/* FROM mail.jar */
final class MimeUtility {
// This class cannot be instantiated
private MimeUtility() { }
private static final boolean ignoreUnknownEncoding =
PropUtil.getBooleanSystemProperty(
"mail.mime.ignoreunknownencoding", false);
Decode the given input stream. The Input stream returned is
the decoded input stream. All the encodings defined in RFC 2045
are supported here. They include "base64", "quoted-printable",
"7bit", "8bit", and "binary". In addition, "uuencode" is also
supported.
In the current implementation, if the
mail.mime.ignoreunknownencoding system property is set to
"true", unknown encoding values are ignored and the
original InputStream is returned.
Params: - is – input stream
- encoding – the encoding of the stream.
Throws: - MessagingException – if the encoding is unknown
Returns: decoded input stream.
/**
* Decode the given input stream. The Input stream returned is
* the decoded input stream. All the encodings defined in RFC 2045
* are supported here. They include "base64", "quoted-printable",
* "7bit", "8bit", and "binary". In addition, "uuencode" is also
* supported. <p>
*
* In the current implementation, if the
* <code>mail.mime.ignoreunknownencoding</code> system property is set to
* <code>"true"</code>, unknown encoding values are ignored and the
* original InputStream is returned.
*
* @param is input stream
* @param encoding the encoding of the stream.
* @return decoded input stream.
* @exception MessagingException if the encoding is unknown
*/
public static InputStream decode(InputStream is, String encoding)
throws DecodingException {
if (encoding.equalsIgnoreCase("base64"))
return new BASE64DecoderStream(is);
else if (encoding.equalsIgnoreCase("quoted-printable"))
return new QPDecoderStream(is);
else if (encoding.equalsIgnoreCase("uuencode") ||
encoding.equalsIgnoreCase("x-uuencode") ||
encoding.equalsIgnoreCase("x-uue"))
return new UUDecoderStream(is);
else if (encoding.equalsIgnoreCase("binary") ||
encoding.equalsIgnoreCase("7bit") ||
encoding.equalsIgnoreCase("8bit"))
return is;
else {
if (!ignoreUnknownEncoding) {
throw new DecodingException("Unknown encoding: " + encoding);
}
return is;
}
}
}