java - MimeMessage 内容传输编码问题

Question

大家好... 我希望有人能给我一些关于我遇到的问题的线索。

阅读 MimeMessage 的 getInputStream() 的 Javadoc，它说“返回此消息内容的已解码输入流” 然而，这不是我所经历的。输出未解码。例如，如果我有一条消息，则如下

Date: Wed, 24 Feb 2010 11:29:13 +1100
From: xxxxxxxxx
To: xxxxxxxxxxxx
Message-ID: <4B8472D9.5050901@xxxxxxxxx>
Subject: xxxxxxxxxxxxxxxxxx
MIME-Version: 1.0
Content-Type: multipart/mixed;
 boundary="------------000801030004000206000901"
Content-Transfer-Encoding: quoted-printable
Organization: xxxxxxxxxxxxxxxxxx
User-Agent: Thunderbird 2.0.0.23 (Windows/20090812)

This is a multi-part message in MIME format.
--------------000801030004000206000901
Content-Type: text/plain; charset=3DISO-8859-1; format=3Dflowed
Content-Transfer-Encoding: 7bit

!

--------------000801030004000206000901
Content-Type: text/plain;
 name=3D"bla.bla"
Content-Transfer-Encoding: 8bit
Content-Disposition: inline;
filename=3D"bla.bla"

 my.username =3D holly
my.host =3D molly
--------------000801030004000206000901--

然后，假设我有一个用上述内容构造的名为“m”的对象，然后调用 m.getInputStream() 并将输出转储到屏幕上显示那些“=3D”字符集。 我做错了什么？

如果我使用 QPDecoderStream 来解码 m.getInputStream() 的输出，那么结果当然是正确的。然而，它达不到目的，因为 Javadoc 说 getInputStream() 返回一个已解码的输入流。

Answer 1

此处的问题是消息格式错误。 You're not allowed to set Content-Transfer-Encoding to quoted-printable on a multipart part :

If a Content-Transfer-Encoding header field appears as part of a message header, it applies to the entire body of that message. If a Content-Transfer-Encoding header field appears as part of an entity's headers, it applies only to the body of that entity. If an entity is of type "multipart" the Content-Transfer-Encoding is not permitted to have any value other than "7bit", "8bit" or "binary".

您可能可以获取顶级 MimeMessage 的解码内容流并从中实例化 MimeMultipart，但这只是解决了损坏消息的基本问题.