JavaMail邮件发送解析

旧城等待， 2022-06-14 07:13 178阅读 0赞

电子邮件的应用非常广泛，例如在某网站注册了一个账户，自动发送一封欢迎邮件，通过邮件找回密码，自动批量发送活动信息等。电子邮件在网络中传输和网页一样需要遵从特定的协议，常用的电子邮件协议包括 SMTP，POP3，IMAP。其中邮件的创建和发送只需要用到 SMTP协议，所有本文也只会涉及到SMTP协议。SMTP 是 Simple Mail Transfer Protocol 的简称，即简单邮件传输协议。在邮件寄送方面，Java EE的解决方案是JavaMail，本文简要介绍JavaMail的使用。

要使用JavaMail进行邮件传送，首先必须创建代表当次邮件会话的javax.mail.Session对象，Session中包括了SMTP邮件服务器地址、连接端口、用户名、密码等信息。以连接163邮件为例，可以创建Session对象：

properties = new Properties();
    // 设置发送邮件的邮件服务器的属性（这里使用网易的smtp服务器）
    properties.put("mail.smtp.host", "smtp.163.com");
    properties.setProperty("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
    properties.setProperty("mail.smtp.socketFactory.fallback", "false");
    properties.setProperty("mail.smtp.port", "465");
    properties.setProperty("mail.smtp.socketFactory.port", "465");
    // 需要经过授权，也就是有户名和密码的校验，这样才能通过验证
    properties.setProperty("mail.smtp.auth", "true");
    Session session = Session.getDefaultInstance(properties,
        new Authenticator() {
            protected PasswordAuthentication getPasswordAuthentication() {
                    return new PasswordAuthentication(username, password);
                }
        });

其中username必须是163邮箱的用户名，password必须是163邮件的授权码，所以163邮箱必须开启POP3/SMTP服务和IMAP/SMTP服务，因为程序属于第三方登录（类似于Foxmail这样的第三方邮件客户端），所以登录密码必须使用163的授权码。

在取得代表当次邮件传送会话的Session对象之后，接着要创建邮件信息，设定发信人、收信人、主题、传送日期与邮件本文：

Message message = new MimeMessage(session);
    // 加载发件人地址
    message.setFrom(new InternetAddress(from));
    // 加载收件人地址
    message.setRecipient(Message.RecipientType.TO, new InternetAddress(to));
    // 加载标题
    message.setSubject(subject);
    message.setSentDate(new Date());
    message.setText(text);

最后再以javax.mail.Transport的静态send()方法传送信息：

Transport.send(message);

## **1、设置实验邮箱** ##

登录自己的163邮箱，进入设置菜单，开启 POP3/SMTP服务和IMAP/SMTP服务的结果如图所示。

![SouthEast][]

点击左侧导航栏里的客户端授权密码，可以设置授权码。

![SouthEast 1][]

## **2、发送纯文字邮件** ##

首先创建一个Dynamic Web Project，把下载好的mail.jar 作为类库加入工程，这里不多说。

简单的邮件发送网页：

![SouthEast 2][]

Servlet代码：

package cc.openhome;
    import java.io.IOException;
    import java.util.Date;
    import java.util.Properties;
    import javax.mail.Authenticator;
    import javax.mail.Message;
    import javax.mail.MessagingException;
    import javax.mail.PasswordAuthentication;
    import javax.mail.Session;
    import javax.mail.Transport;
    import javax.mail.internet.AddressException;
    import javax.mail.internet.InternetAddress;
    import javax.mail.internet.MimeMessage;
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebInitParam;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    @WebServlet(
            urlPatterns = { "/mail.do" }, 
            initParams = { 
                    @WebInitParam(name = "mailHost", value = "smtp.163.com"), 
                    @WebInitParam(name = "mailPort", value = "465"), 
                    @WebInitParam(name = "username", value = "xxxx@163.com"), 
                    @WebInitParam(name = "password", value = "xxxxx")
            })
    public class MailServlet extends HttpServlet { 
        private static final long serialVersionUID = 1L;
        private String mailHost;
        private String mailPort;
        private String username;
        private String password;
        private Properties properties;
    
        @Override
        public void init() {
            mailHost = getServletConfig().getInitParameter("mailHost");
            mailPort = getServletConfig().getInitParameter("mailPort");
            username = getServletConfig().getInitParameter("username");
            password = getServletConfig().getInitParameter("password");
            properties = new Properties();
            // 设置发送邮件的邮件服务器的属性（这里使用网易的smtp服务器）
            properties.put("mail.smtp.host", mailHost);
            properties.setProperty("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
            properties.setProperty("mail.smtp.socketFactory.fallback", "false");
            properties.setProperty("mail.smtp.port", mailPort);
            properties.setProperty("mail.smtp.socketFactory.port", mailPort);
             // 需要经过授权，也就是有户名和密码的校验，这样才能通过验证（一定要有这一条）
            properties.setProperty("mail.smtp.auth", "true");
        }
    
        public MailServlet() {
            super();
            // TODO Auto-generated constructor stub
        }
    
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            // TODO Auto-generated method stub
            response.getWriter().append("Served at: ").append(request.getContextPath());
        }
    
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            // TODO Auto-generated method stub
            request.setCharacterEncoding("UTF-8");
            response.setContentType("text/html;charset=UTF-8");
    
            String from = request.getParameter("from");
            String to = request.getParameter("to");
            String subject = request.getParameter("subject");
            String text = request.getParameter("text");
    
            try {
                Message message = getMessage(from, to, subject, text);
                Transport.send(message);
                response.getWriter().println("<h1>邮件发送成功</h1>");
            } catch (Exception e) {
                throw new ServletException(e);
            }
        }
    
        private Message getMessage(String from, String to, String subject, String text) throws AddressException, MessagingException {
            // PS_02: 连接失败的原因通常为以下几点, 仔细检查代码:
            // (1) 邮箱没有开启 SMTP 服务;
            // (2) 邮箱密码错误, 例如某些邮箱开启了独立密码;
            // (3) 邮箱服务器要求必须要使用 SSL 安全连接;
            // (4) 请求过于频繁或其他原因, 被邮件服务器拒绝服务;
            // (5) 如果以上几点都确定无误, 到邮件服务器网站查找帮助。
            Session session = Session.getDefaultInstance(properties,new Authenticator() {
                protected PasswordAuthentication getPasswordAuthentication() {
                    return new PasswordAuthentication(username, password);
                }
            });
             // 设置为debug模式, 可以在控制台上看到发送邮件的过程
            session.setDebug(true);   
            Message message = new MimeMessage(session);
            // 加载发件人地址
            message.setFrom(new InternetAddress(from));
             // 加载收件人地址
            message.setRecipient(Message.RecipientType.TO, new InternetAddress(to));
            // 加载标题
            message.setSubject(subject);
            message.setSentDate(new Date());
            message.setText(text);
            return message;
        }
    }

在这个Servlet中，将连接SMTP基本信息设定为Servlet初始参数，并且在init()方法中，设定好创建Session对象的必要属性。

发送邮件成功的网页如图所示：

![SouthEast 3][]

收到的测试邮件如图所示：

![SouthEast 4][]

## **3、发送多重内容邮件** ##

如果邮件可以包括HTML或附加文件等多重内容，则必须要有javax.mail.Multipart对象，并在这个对象中增加代表多重内容的javax.mail.internet.MimeBodyPart对象。举个例子来说，如果要让邮件内容包括HTML内容，则可以如下：

// 处理HTML内容
    MimeBodyPart htmlPart = new MimeBodyPart();
    htmlPart.setContent(text, "text/html;charset=UTF-8");
    Multipart multipart = new MimeMultipart();
    multipart.addBodyPart(htmlPart);
    message.setContent(multipart);

如果邮件要附加文件，则可以创建MimeBodyPart，设定文件名与内容之后，再加入MultiPart中：

byte [] file=...;
    MimeBodyPart filePart = new MimeBodyPart();
    filePart.setFileName(MimeUtility.encodeText(filename, "UTF-8", "B"));
    filePart.setContent(file,part.getContentType());

在使用MimeBodyPart的setFileName()设定附件名称时，必须做Mime编码，所以借助MimeUtility.encodeText()方法，在使用setContent()设定内容时，还需指定内容类型。

简单的多重内容邮件发送网页：

![SouthEast 5][]

Servlet代码：

package cc.openhome;
    import java.io.ByteArrayOutputStream;
    import java.io.IOException;
    import java.io.InputStream;
    import java.util.Date;
    import java.util.Properties;
    import javax.mail.Authenticator;
    import javax.mail.Message;
    import javax.mail.MessagingException;
    import javax.mail.Multipart;
    import javax.mail.PasswordAuthentication;
    import javax.mail.Session;
    import javax.mail.Transport;
    import javax.mail.internet.AddressException;
    import javax.mail.internet.InternetAddress;
    import javax.mail.internet.MimeBodyPart;
    import javax.mail.internet.MimeMessage;
    import javax.mail.internet.MimeMultipart;
    import javax.servlet.ServletException;
    import javax.servlet.annotation.MultipartConfig;
    import javax.servlet.annotation.WebInitParam;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.Part;
    import com.sun.xml.internal.messaging.saaj.packaging.mime.internet.MimeUtility;
    
    
    @MultipartConfig
    @WebServlet(
            urlPatterns = { "/multipart.do" }, 
            initParams = { 
                @WebInitParam(name = "mailHost", value = "smtp.163.com"), 
                @WebInitParam(name = "mailPort", value = "465"), 
                @WebInitParam(name = "username", value = "xxxx@163.com"), 
                @WebInitParam(name = "password", value = "xxxxx")
            })
    public class MultiPartMailServlet extends HttpServlet { 
        private static final long serialVersionUID = 1L;
        private String mailHost;
        private String mailPort;
        private String username;
        private String password;
        private Properties properties;
    
        @Override
        public void init() {
            mailHost = getServletConfig().getInitParameter("mailHost");
            mailPort = getServletConfig().getInitParameter("mailPort");
            username = getServletConfig().getInitParameter("username");
            password = getServletConfig().getInitParameter("password");
    
            properties = new Properties();
            // 设置发送邮件的邮件服务器的属性（这里使用网易的smtp服务器）
            properties.put("mail.smtp.host", mailHost);
            properties.setProperty("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
            properties.setProperty("mail.smtp.socketFactory.fallback", "false");
            properties.setProperty("mail.smtp.port", mailPort);
            properties.setProperty("mail.smtp.socketFactory.port", mailPort);
             // 需要经过授权，也就是有户名和密码的校验，这样才能通过验证（一定要有这一条）
            properties.setProperty("mail.smtp.auth", "true");
        }
    
        public MultiPartMailServlet() {
            super();
            // TODO Auto-generated constructor stub
        }
    
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            // TODO Auto-generated method stub
            response.getWriter().append("Served at: ").append(request.getContextPath());
        }
    
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            // TODO Auto-generated method stub
            request.setCharacterEncoding("UTF-8");
            response.setContentType("text/html;charset=UTF-8");
            String from = request.getParameter("from");
            String to = request.getParameter("to");
            String subject = request.getParameter("subject");
            String text = request.getParameter("text");
            Part part = request.getPart("file");
    
            try {
                Message message = getMessage(from, to, subject, text, part);
                Transport.send(message);
                response.getWriter().println("<h1>邮件发送成功</h1>");
            } catch (Exception e) {
                throw new ServletException(e);
            }
        }
    
        private Message getMessage(String from, String to, String subject, String text, Part part) throws AddressException, MessagingException, IOException {
            Session session = Session.getDefaultInstance(properties,new Authenticator() {
                protected PasswordAuthentication getPasswordAuthentication() {
                    return new PasswordAuthentication(username, password);
                }
            });
             // 设置为debug模式, 可以在控制台上看到发送邮件的过程
            session.setDebug(true);   
            Message message = new MimeMessage(session);
            // 加载发件人地址
            message.setFrom(new InternetAddress(from));
             // 加载收件人地址
            message.setRecipient(Message.RecipientType.TO, new InternetAddress(to));
            // 加载标题
            message.setSubject(subject);
            message.setSentDate(new Date());
            // 处理HTML内容
            MimeBodyPart htmlPart = new MimeBodyPart();
            htmlPart.setContent(text, "text/html;charset=UTF-8");
            Multipart multipart = new MimeMultipart();
            multipart.addBodyPart(htmlPart);
            //如果有上传文件，就可以取得文件名，处理文件内容
            String filename = getFilename(part);
            if(!"".equals(filename)) {
                MimeBodyPart filePart = new MimeBodyPart();
                filePart.setFileName(MimeUtility.encodeText(filename, "UTF-8", "B"));
                filePart.setContent(getBytes(part), part.getContentType());
                multipart.addBodyPart(filePart);
            }
            message.setContent(multipart);
    
            return message;
        }
    
        private String getFilename(Part part) {
            String header = part.getHeader("Content-Disposition");
            String filename = header.substring(header.indexOf("filename=\"") + 10, header.lastIndexOf("\""));
            return filename;
        }
    
        private byte[] getBytes(Part part) throws IOException {
            InputStream in = part.getInputStream();
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            byte[] buffer = new byte[1024];
            int length = -1;
            while((length = in.read(buffer)) != -1) {
                out.write(buffer, 0, length);
            }
            in.close();
            out.close();
            return out.toByteArray();
        }
    }

成功收到的邮件如图所示：

![SouthEast 6][]

由于窗体会以multipart/form-data类型送出，在Servlet3.0中，如果要使用HttpServletRequest的getPart()等方法，必须加注@MultipartConfig。

[SouthEast]: /images/20220614/a7b4caec8b0a4c3c9aa10f69b4065d90.png
[SouthEast 1]: /images/20220614/94a46b2b75c44121aea597d7d2083776.png
[SouthEast 2]: /images/20220614/a55b60cad6524671be76a758eac20b07.png
[SouthEast 3]: /images/20220614/6808962040b34cb78333813094f554ca.png
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[SouthEast 5]: /images/20220614/84937004b3a94217bfa948b578652fde.png
[SouthEast 6]: /images/20220614/d5ebc8e3eddf42129ac30399585a9423.png