以下内容引用自http://wiki.jikexueyuan.com/project/servlet/sending-email.html：
使用Servlet发送一封电子邮件是非常简单的，但是开始之前必须在计算机上安装JavaMail API和Java Activation Framework(JAF)。
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可以从Java标准网站下载最新版本的JavaMail版本 1.2
- 可以从Java标准网站下载最新版本的JAF版本 1.1.1
下载并解压缩这些文件，在新创建的顶级目录中会发现这两个应用程序的一些jar文件。需要把mail.jar和activation.jar文件添加到CLASSPATH中。
POM项目添加如下依赖：
<!-- JavaMail Library --> <!-- http://mvnrepository.com/artifact/com.sun.mail/javax.mail --> <dependency> <groupId>com.sun.mail</groupId> <artifactId>javax.mail</artifactId> <version>1.5.6</version> </dependency>
一、发送一封简单的电子邮件
//File Name SendEmail.java import java.io.*; import java.util.*; import javax.servlet.*; import javax.servlet.http.*; import javax.mail.*; import javax.mail.internet.*; import javax.activation.*; public class SendEmail extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // Recipient's email ID needs to be mentioned. String to = "abcd@gmail.com"; // Sender's email ID needs to be mentioned String from = "web@gmail.com"; // Assuming you are sending email from localhost String host = "localhost";// This is SMTP Server,Ex:smtp.163.com // set email username String user = "user"; // set email password String password = "password"; // Get system properties Properties properties = System.getProperties(); // Setup mail server properties.setProperty("mail.smtp.host", host); properties.setProperty("mail.user", user); properties.setProperty("mail.password", password); // Get the default Session object. Session session = Session.getDefaultInstance(properties); // Set response content type response.setContentType("text/html"); PrintWriter out = response.getWriter(); try { // Create a default MimeMessage object. MimeMessage message = new MimeMessage(session); // Set From: header field of the header. message.setFrom(new InternetAddress(from)); // Set To: header field of the header. message.addRecipient(Message.RecipientType.TO, new InternetAddress(to)); // Set Subject: header field message.setSubject("This is the Subject Line!"); // Now set the actual message message.setText("This is actual message"); // Send message Transport.send(message); String title = "Send Email"; String res = "Sent message successfully...."; String docType = "<!doctype html public "-//w3c//dtd html 4.0 " + "transitional//en"> "; out.println(docType + "<html> " + "<head><title>" + title + "</title></head> " + "<body bgcolor="#f0f0f0"> " + "<h1 align="center">" + title + "</h1> " + "<p align="center">" + res + "</p> " + "</body></html>"); } catch (MessagingException mex) { mex.printStackTrace(); } } }
现在编译上述Servlet并在web.xml文件中创建以下条目：
.... <servlet> <servlet-name>SendEmail</servlet-name> <servlet-class>SendEmail</servlet-class> </servlet> <servlet-mapping> <servlet-name>SendEmail</servlet-name> <url-pattern>/SendEmail</url-pattern> </servlet-mapping> ....
如果想把一封电子邮件发送给多个收件人，那么使用下面的方法来指定多个电子邮件ID：
void addRecipients(Message.RecipientType type, Address[] addresses) throws MessagingException
这里是对参数的描述：
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type：这将被设置为TO、CC或BCC。这里CC代表抄送且BCC代表密件抄送。例如Message.RecipientType.TO。
- addresses：这是电子邮件ID的数组。当指定电子邮件ID时，需要使用InternetAddress()方法。
二、发送一封HTML电子邮件
这个例子与上一个例子非常相似，除了在这里使用的是setContent()方法来设置内容，它的第二个参数为“text/html”用来指定HTML内容是包含在消息中的。
使用这个实例，可以发送内容大小不限的HTML内容。
//File Name SendEmail.java import java.io.*; import java.util.*; import javax.servlet.*; import javax.servlet.http.*; import javax.mail.*; import javax.mail.internet.*; import javax.activation.*; public class SendEmail1 extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // Recipient's email ID needs to be mentioned. String to = "abcd@gmail.com"; // Sender's email ID needs to be mentioned String from = "web@gmail.com"; // Assuming you are sending email from localhost String host = "localhost";//This is SMTP Server,Ex:smtp.163.com // set email username String user = "user"; // set email password String password = "password"; // Get system properties Properties properties = System.getProperties(); // Setup mail server properties.setProperty("mail.smtp.host", host); properties.setProperty("mail.user", user); properties.setProperty("mail.password", password); // Get the default Session object. Session session = Session.getDefaultInstance(properties); // Set response content type response.setContentType("text/html"); PrintWriter out = response.getWriter(); try { // Create a default MimeMessage object. MimeMessage message = new MimeMessage(session); // Set From: header field of the header. message.setFrom(new InternetAddress(from)); // Set To: header field of the header. message.addRecipient(Message.RecipientType.TO, new InternetAddress(to)); // Set Subject: header field message.setSubject("This is the Subject Line!"); // Send the actual HTML message, as big as you like message.setContent("<h1>This is actual message</h1>", "text/html"); // Send message Transport.send(message); String title = "Send Email"; String res = "Sent message successfully...."; String docType = "<!doctype html public "-//w3c//dtd html 4.0 " + "transitional//en"> "; out.println(docType + "<html> " + "<head><title>" + title + "</title></head> " + "<body bgcolor="#f0f0f0"> " + "<h1 align="center">" + title + "</h1> " + "<p align="center">" + res + "</p> " + "</body></html>"); } catch (MessagingException mex) { mex.printStackTrace(); } } }
现在编译上述Servlet并在web.xml文件中创建以下条目：
<servlet> <servlet-name>SendEmail</servlet-name> <servlet-class>com.jsoft.testservletbasics.SendEmail1</servlet-class> </servlet> <servlet-mapping> <servlet-name>SendEmail</servlet-name> <url-pattern>/SendEmail</url-pattern> </servlet-mapping>
三、在电子邮件中发送附件
//File Name SendEmail.java import java.io.*; import java.util.*; import javax.servlet.*; import javax.servlet.http.*; import javax.mail.*; import javax.mail.internet.*; import javax.activation.*; public class SendFile extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // Recipient's email ID needs to be mentioned. String to = "abcd@gmail.com"; // Sender's email ID needs to be mentioned String from = "web@gmail.com"; // Assuming you are sending email from localhost String host = "localhost";// This is SMTP Server,Ex:smtp.163.com // set email username String user = "user"; // set email password String password = "password"; // Get system properties Properties properties = System.getProperties(); // Setup mail server properties.setProperty("mail.smtp.host", host); properties.setProperty("mail.user", user); properties.setProperty("mail.password", password); // Get the default Session object. Session session = Session.getDefaultInstance(properties); // Set response content type response.setContentType("text/html"); PrintWriter out = response.getWriter(); try { // Create a default MimeMessage object. MimeMessage message = new MimeMessage(session); // Set From: header field of the header. message.setFrom(new InternetAddress(from)); // Set To: header field of the header. message.addRecipient(Message.RecipientType.TO, new InternetAddress(to)); // Set Subject: header field message.setSubject("This is the Subject Line!"); // Create the message part BodyPart messageBodyPart = new MimeBodyPart(); // Fill the message messageBodyPart.setText("This is message body"); // Create a multipar message Multipart multipart = new MimeMultipart(); // Set text message part multipart.addBodyPart(messageBodyPart); // Part two is attachment messageBodyPart = new MimeBodyPart(); String filename = "file.txt"; DataSource source = new FileDataSource(filename); messageBodyPart.setDataHandler(new DataHandler(source)); messageBodyPart.setFileName(filename); multipart.addBodyPart(messageBodyPart); // Send the complete message parts message.setContent(multipart); // Send message Transport.send(message); String title = "Send Email"; String res = "Sent message successfully...."; String docType = "<!doctype html public "-//w3c//dtd html 4.0 " + "transitional//en"> "; out.println(docType + "<html> " + "<head><title>" + title + "</title></head> " + "<body bgcolor="#f0f0f0"> " + "<h1 align="center">" + title + "</h1> " + "<p align="center">" + res + "</p> " + "</body></html>"); } catch (MessagingException mex) { mex.printStackTrace(); } } }
现在编译上述Servlet并在web.xml文件中创建以下条目：
<servlet> <servlet-name>SendEmail</servlet-name> <servlet-class>com.jsoft.testservletbasics.SendFile</servlet-class> </servlet> <servlet-mapping> <servlet-name>SendEmail</servlet-name> <url-pattern>/SendEmail</url-pattern> </servlet-mapping>
四、用户身份认证部分
如果需要向电子邮件服务器提供用户ID和密码来进行身份认证，那么可以设置如下所示的属性：
props.setProperty("mail.user", "myuser");
props.setProperty("mail.password", "mypwd");
电子邮件发送机制的其余部分与上面解释的一致。
测试工程：https://github.com/easonjim/5_java_example/tree/master/servletbasics/test16