JavaMail:带附件的邮件格式解析

待我称王封你为后i 2022-01-11 07:45 589阅读 0赞

最近上课时，用到了JavaMail。JavaMail可以使用POP3协议接受邮件，可用来实现邮件发布文章功能。那么具体该怎么做呢？这就必须先要明白带附件的邮件的格式。当收到邮件后进行解析，我们可以看到如下的邮件代码（注意为了便于阅读，已经将分隔符替换为比较容易阅读的格式）：

Received: from 127.0.0.1 by FMS4711; Fri, 25 Jul 2008 13:02:36 +0800  
Date: Fri, 25 Jul 2008 13:02:36 +0800  
From: "beansoft" <[beansoft@earth.org][beansoft_earth.org]>  
To: "hp" <[hp@earth.org][hp_earth.org]>  
Subject: =?gb2312?B?wb249ri9vP4=?=  
Message-ID: <[200807251302355150265@earth.org][200807251302355150265_earth.org]>  
X-mailer: Foxmail 6, 13, 102, 15 \[cn\]  
Mime-Version: 1.0

Content-Type: multipart/mixed;  
    boundary="===========分割一============"

This is a multi-part message in MIME format.

\--===========分割一============  
  Content-Type: multipart/alternative;  
    boundary="===========分割2================="

--===========分割2=================  
  Content-Type: text/plain;  
    charset="gb2312"  
  Content-Transfer-Encoding: 7bit

Body

--===========分割2=================  
  Content-Type: text/html;  
    charset="gb2312"  
  Content-Transfer-Encoding: 7bit

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">  
  <HTML><HEAD>  
  <META http-equiv=Content-Type content="text/html; charset=GB2312">  
  <META content="MSHTML 6.00.5730.13" name=GENERATOR><LINK  
  href="BLOCKQUOTE\{margin-Top: 0px; margin-Bottom: 0px; margin-Left: 2em\}"  
  rel=stylesheet></HEAD>  
  <BODY style="FONT-SIZE: 10pt; MARGIN: 10px; FONT-FAMILY: verdana">  
  <DIV><FONT face=Verdana size=2><STRONG>Body</STRONG></FONT></DIV><FONT  
  face=Verdana size=2>  
  <DIV>&nbsp;</DIV></FONT></BODY></HTML>

\--===========分割2=================--

\--===========分割一============  
Content-Type: application/octet-stream;  
    name="String2Java.jpg"  
Content-Transfer-Encoding: base64  
Content-Disposition: attachment;  
    filename="String2Java.jpg"

/9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAAgGBgcGBQgHBwcJCQgKDBQNDAsLDBkSEw8UHRofHh0a  
oAKKKKACiiigAooooA//2Q==

\--===========分割一============  
Content-Type: application/octet-stream;  
    name="FoxmailUpdate.log"  
Content-Transfer-Encoding: base64  
Content-Disposition: attachment;  
    filename="FoxmailUpdate.log"

OAAAAPgb7GHGsCG8a8W48hC9ihdb8CcIlHlKXcYwNP+8dPRB30zrsI2K4TPJP0gYLB3Cua0JRtBL  
g/z8XA5PJneuwd9Uiu0nEH4Iobo+12oK9hsKK7xFXYhw++a50FHQuCDXX5kpF2d6

\--===========分割一============--

它对应JavaMail的Message对象，一个Message对象又会有多个子对象如MultiPart对象，更特殊的是整个邮件内容为一个大的MultiPart，然而邮件的正文则在嵌套的一个子MultiPart中，如果不了解这种组织结构，就可能无法正确获得邮件的正文。此结构如下图所示：

邮件Message

头部(主题, 发件人信息等)  
   
MultiPart邮件全部内容, 包含正文和附件

正文 MultiPart

文本正文 text/plain

Content-Type: text/plain;charset="gb2312"

HTML网页格式 text/html

Content-Type: text/html;charset="gb2312"

附件1

Content-Type: application/octet-stream;

name="String2Java.jpg"

Content-Transfer-Encoding: base64

Content-Disposition: attachment;

filename="String2Java.jpg"

附件2

Content-Type: application/octet-stream;

name="FoxmailUpdate.log"

Content-Transfer-Encoding: base64

Content-Disposition: attachment;

filename="FoxmailUpdate.log"

有了这些资料，我们就可以来解析邮件了，代码如下：

import java.io.FileOutputStream;  
import java.io.IOException;  
import java.util.Properties;

import javax.mail.Address;  
import javax.mail.BodyPart;  
import javax.mail.FetchProfile;  
import javax.mail.Flags;  
import javax.mail.Folder;  
import javax.mail.Message;  
import javax.mail.MessagingException;  
import javax.mail.Multipart;  
import javax.mail.NoSuchProviderException;  
import javax.mail.Part;  
import javax.mail.Session;  
import javax.mail.Store;  
import javax.mail.internet.InternetAddress;  
import javax.mail.internet.MimeMultipart;

/\*\*  
\* 邮件接受测试  
\*  
\*/  
public class POP3MailReceiverTest \{

public POP3MailReceiverTest() \{  
        try \{  
            // 1. 设置连接信息, 生成一个 Session  
            Properties props = new Properties();  
            props.put("mail.transport.protocol", "pop3");// POP3 收信协议  
            props.put("mail.pop.port", "110");  
            // props.put("mail.debug", "true");// 调试

Session session = Session.getInstance(props);

// 2. 获取 Store 并连接到服务器  
            Store store = session.getStore("pop3");  
            store.connect("localhost", "[hp@earth.org][hp_earth.org]", "1234");  
            // 3. 通过 Store 打开默认目录 Folder  
            Folder folder = store.getDefaultFolder();// 默认父目录  
            if (folder == null) \{

System.out.println("服务器不可用");  
                return;  
                // System.exit(1);  
            \}

//            System.out.println("默认信箱名:" + folder.getName());  
//  
//            Folder\[\] folders = folder.list();// 默认目录列表  
//  
//            System.out.println("默认目录下的子目录数: " + folders.length);

Folder popFolder = folder.getFolder("INBOX");// 获取收件箱  
            popFolder.open(Folder.READ\_WRITE);// 可读邮件,可以删邮件的模式打开目录  
            // 4. 列出来收件箱 下所有邮件  
            Message\[\] messages = popFolder.getMessages();  
            // 取出来邮件数  
            int msgCount = popFolder.getMessageCount();  
            System.out.println("共有邮件: " + msgCount + "封");

// FetchProfile fProfile = new FetchProfile();// 选择邮件的下载模式,  
            // 根据网速选择不同的模式  
            // fProfile.add(FetchProfile.Item.ENVELOPE);  
            // folder.fetch(messages, fProfile);// 选择性的下载邮件

// 5. 循环处理每个邮件并实现邮件转为新闻的功能  
            for (int i = 0; i < msgCount; i++) \{  
                Message msg = messages\[i\];// 单个邮件  
                // 发件人信息  
                Address\[\] froms = msg.getFrom();  
                if(froms != null) \{  
                    System.out.println("发件人信息:" + froms\[0\]);  
                    InternetAddress addr = (InternetAddress)froms\[0\];  
                    System.out.println("发件人地址:" + addr.getAddress());  
                    System.out.println("发件人显示名:" + addr.getPersonal());  
                \}  
                News news = new News();// 生成新闻对象  
                System.out.println("邮件主题:" + msg.getSubject());  
                news.setTitle(msg.getSubject());

// getContent() 是获取包裹内容, Part 相当于外包装  
                Multipart multipart = (Multipart) msg.getContent();// 获取邮件的内容, 就一个大包裹,  
                                                                // MultiPart  
                                                                    // 包含所有邮件内容(正文+附件)  
                System.out.println("邮件共有" + multipart.getCount() + "部分组成");

// 依次处理各个部分  
                for (int j = 0, n = multipart.getCount(); j < n; j++) \{  
                    System.out.println("处理第" + j + "部分");  
                    Part part = multipart.getBodyPart(j);//解包, 取出 MultiPart的各个部分, 每部分可能是邮件内容,  
                    // 也可能是另一个小包裹(MultipPart)

// 判断此包裹内容是不是一个小包裹, 一般这一部分是 正文 Content-Type: multipart/alternative  
                    if (part.getContent() instanceof Multipart) \{  
                        Multipart p = (Multipart) part.getContent();// 转成小包裹  
                        System.out.println("小包裹中有" + p.getCount() + "部分");  
                        // 列出小包裹中所有内容  
                        for (int k = 0; k < p.getCount(); k++) \{  
                            System.out.println("小包裹内容:" + p.getBodyPart(k).getContent());  
                            System.out.println("内容类型:"  
                                    + p.getBodyPart(k).getContentType());  
                            if(p.getBodyPart(k).getContentType().startsWith("text/plain")) \{  
                                // 处理文本正文  
                                news.setBody(p.getBodyPart(k).getContent() + "");  
                            \} else \{  
                                // 处理 HTML 正文  
                                news.setBody(p.getBodyPart(k).getContent() + "");  
                            \}  
                        \}  
                    \}

// Content-Disposition: attachment;    filename="String2Java.jpg"  
                    String disposition = part.getDisposition();// 处理是否为附件信息  
                    if (disposition != null) \{

System.out.println("发现附件: " + part.getFileName());  
                        System.out.println("内容类型: " + part.getContentType());  
                        System.out.println("附件内容:" + part.getContent());  
                        java.io.InputStream in = part.getInputStream();// 打开附件的输入流  
                        // 读取附件字节并存储到文件中  
                        java.io.FileOutputStream out = new FileOutputStream(part.getFileName());  
                        int data;  
                        while((data = in.read()) != -1) \{  
                            out.write(data);  
                        \}  
                        in.close();  
                        out.close();  
                    \}  
                \}  
                // \}  
                // TODO newsDAO.save(news); // 将邮件所携带的信息作为新闻存储起来

// 6. 删除单个邮件, 标记一下邮件需要删除, 不会真正执行删除操作  
                // msg.setFlag(Flags.Flag.DELETED, true);  
            \}

// 7. 关闭 Folder 会真正删除邮件, false 不删除  
            popFolder.close(true);  
            // 8. 关闭 store, 断开网络连接  
            store.close();  
        \} catch (NoSuchProviderException e) \{  
            // TODO Auto-generated catch block  
            e.printStackTrace();  
        \} catch (Exception e) \{  
            // TODO Auto-generated catch block  
            e.printStackTrace();  
        \}  
    \}

/\*\*  
     \* @param args  
     \*/  
    public static void main(String\[\] args) \{  
        new POP3MailReceiverTest();

[beansoft_earth.org]: mailto:beansoft@earth.org
[hp_earth.org]: mailto:hp@earth.org
[200807251302355150265_earth.org]: mailto:200807251302355150265@earth.org