此答案扩展 yurin的回答。他提出的问题是 MimeMultipart 的内容本身可能是另一个 MimeMultipart 。下面的 getTextFromMimeMultipart（）方法在这种情况下对内容进行递归，直到消息体被完全解析为止。

This answer extends yurin's answer. The issue he brought up was that the content of a MimeMultipart may itself be another MimeMultipart. The getTextFromMimeMultipart() method below recurses in such cases on the content until the message body has been fully parsed.

private String getTextFromMessage(Message message) throws MessagingException, IOException {
    String result = "";
    if (message.isMimeType("text/plain")) {
        result = message.getContent().toString();
    } else if (message.isMimeType("multipart/*")) {
        MimeMultipart mimeMultipart = (MimeMultipart) message.getContent();
        result = getTextFromMimeMultipart(mimeMultipart);
    }
    return result;
}

private String getTextFromMimeMultipart(
        MimeMultipart mimeMultipart)  throws MessagingException, IOException{
    String result = "";
    int count = mimeMultipart.getCount();
    for (int i = 0; i < count; i++) {
        BodyPart bodyPart = mimeMultipart.getBodyPart(i);
        if (bodyPart.isMimeType("text/plain")) {
            result = result + "\n" + bodyPart.getContent();
            break; // without break same text appears twice in my tests
        } else if (bodyPart.isMimeType("text/html")) {
            String html = (String) bodyPart.getContent();
            result = result + "\n" + org.jsoup.Jsoup.parse(html).text();
        } else if (bodyPart.getContent() instanceof MimeMultipart){
            result = result + getTextFromMimeMultipart((MimeMultipart)bodyPart.getContent());
        }
    }
    return result;
}