要发送一封电子邮件，使用Servlet是很简单的，但首先，你的机器上已经安装了JavaMail API和Java激活框架（JAF）。
您可以从Java标准网站下载最新版本 JavaMail (Version 1.2)
从Java的标准的网站，您可以下载最新版本 JAF (Version 1.1.1)
下载并解压缩这些文件，在新创建的顶层目录，你会发现两个应用程序的jar文件。需要在CLASSPATH添加了mail.jar 和activation.jar文件。
下面是一个例子，从您的计算机发送一个简单的电子邮件。这里假设您的本地主机连接到互联网，并有足够的能力来发送电子邮件。同时确保所有的jar文件从Java电子邮件API包和JAF包ARA在CLASSPATH中。
// 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";
// Get system properties
Properties properties = System.getProperties();
// Setup mail server - by www.gitbook.net
properties.setProperty("mail.smtp.host", host);
// 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\">\n";
out.println(docType +
"<html>\n" +
"<head><title>" + title + "</title></head>\n" +
"<body bgcolor=\"#f0f0f0\">\n" +
"<h1 align=\"center\">" + title + "</h1>\n" +
"<p align=\"center\">" + res + "</p>\n" +
"</body></html>");
}catch (MessagingException mex) {
mex.printStackTrace();
}
}
}
现在让我们来编译上面的servlet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>
....
现在调用这个servlet，使用URL http://localhost:8080/SendEmail，会发送邮件到电子邮件ID为abcd@gmail.com将显示以下回应：
Send EmailSent message successfully.... |
如果你想发送电子邮件给多个收件人，然后下面的方法将被用来指定多个电子邮件ID：
void addRecipients(Message.RecipientType type,
Address[] addresses)
throws MessagingException
下面的参数说明：
type: 这将被设定为TO，CC或BCC。在这里，CC代表抄送BCC的Black Carbon复制。例如Message.RecipientType.
addresses: 这是数组的电子邮件ID。您将需要使用InternetAddress()方法，同时指定电子邮件ID
下面是一个例子，从您的计算机发送HTML格式的电子邮件。这里假设您的本地主机连接到互联网，并有足够的能力来发送电子邮件。同时确保所有的jar文件从Java电子邮件API包和JAF包ARA在CLASSPATH。
这个例子是前一个非常相似的，但在这里我们使用的是setContent()方法来设置内容的第二个参数是“text/html的”指定HTML内容包含在消息中。
使用这个例子中，你可以发送喜欢的HTML内容，内容的大小一般不受限制。
// 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";
// Get system properties - by www.gitbook.net
Properties properties = System.getProperties();
// Setup mail server
properties.setProperty("mail.smtp.host", host);
// 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\">\n";
out.println(docType +
"<html>\n" +
"<head><title>" + title + "</title></head>\n" +
"<body bgcolor=\"#f0f0f0\">\n" +
"<h1 align=\"center\">" + title + "</h1>\n" +
"<p align=\"center\">" + res + "</p>\n" +
"</body></html>");
}catch (MessagingException mex) {
mex.printStackTrace();
}
}
}
编译并运行上面的servlet发送HTML邮件在一个给定的电子邮件ID。
下面是一个例子，从您的计算机发送带有附件的电子邮件。这里假设您的本地主机连接到互联网，并有足够的能力来发送电子邮件。
// 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";
// Get system properties
Properties properties = System.getProperties();
// Setup mail server - by www.gitbook.net
properties.setProperty("mail.smtp.host", host);
// 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\">\n";
out.println(docType +
"<html>\n" +
"<head><title>" + title + "</title></head>\n" +
"<body bgcolor=\"#f0f0f0\">\n" +
"<h1 align=\"center\">" + title + "</h1>\n" +
"<p align=\"center\">" + res + "</p>\n" +
"</body></html>");
}catch (MessagingException mex) {
mex.printStackTrace();
}
}
}
编译并运行上面的servlet发送一个文件作为附件一起在一个给定的电子邮件ID消息。
如果需要提供用户ID和密码的电子邮件服务器进行身份验证的目的，那么你可以设置这些属性，如下所示：
props.setProperty("mail.user", "myuser");
props.setProperty("mail.password", "mypwd");
如上面所解释的电子邮件发送机制，其余部分将保持。