Servlets 简明教程

Servlets - Sending Email

使用 Servlet 发送电子邮件非常简单，但前提是您应该在计算机上安装 JavaMail API 和 Java Activation Framework (JAF) 。

你可以从 Java 标准网站下载 JavaMail (Version 1.2) 的最新版本。
你可以从 Java 标准网站下载 JAF (Version 1.1.1) 的最新版本。

下载并解压缩这些文件，在新建的顶层目录中，你可以找到这两个应用程序的多个 jar 文件。你需要在你的 CLASSPATH 中添加 mail.jar 和 activation.jar 文件。

Send a Simple Email

以下示例演示从您的计算机发送一封简单的电子邮件。这里假设您的 localhost 已连接到互联网并能够发送电子邮件。同时，确保 CLASSPATH 中存在 Java Email API 包和 JAF 包中的所有 jar 文件。

// 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
      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();
      }
   }
}

现在让我们编译上述 servlet，并在 web.xml 中创建以下项

....
 <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>
....

现在使用 URL [role="bare"] [role="bare"]http://localhost:8080/SendEmail 调用此 servlet，它将向给定的电子邮件 ID abcd@gmail.com 发送一封电子邮件，并会显示以下响应 −

Send Email
Sent message successfully....

如果您要向多个收件人发送电子邮件，则将使用以下方法指定多个电子邮件 ID −

void addRecipients(Message.RecipientType type, Address[] addresses)
throws MessagingException

以下是参数说明 −

type − 这将设置为 TO、CC 或 BCC。这里的 CC 表示抄送，BCC 表示密件抄送。示例 Message.RecipientType.TO
addresses − 这是电子邮件 ID 数组。您需要在指定电子邮件 ID 时使用 InternetAddress() 方法。

Send an HTML Email

以下示例演示从您的计算机发送一封 HTML 电子邮件。这里假设您的 localhost 已连接到互联网并能够发送电子邮件。同时，请确保 CLASSPATH 中存在 Java Email API 包和 JAF 包中的所有 jar 文件。

这个示例与之前的示例非常类似，只不过这里我们使用 setContent() 方法设置内容，其第二个参数为“text/html”，用于指定邮件中包含 HTML 内容。

使用这个示例，你可以发送任意长度的 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 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
      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();
      }
   }
}

编译并运行上述 servlet，以便在给定的电子邮件 ID 上发送 HTML 邮件。

Send Attachment in Email

以下示例演示从您的计算机发送带有附件的电子邮件。这里假设您的 localhost 已连接到互联网并能够发送电子邮件。

// 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
      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();
      }
   }
}

编译并运行上述 servlet，以便将一个文件作为附件与邮件一起发送到给定的电子邮件 ID。

User Authentication Part

如果需要向电子邮件服务器提供用户 ID 和密码以用于身份验证目的，则您可以按如下方式设置这些属性 −

 props.setProperty("mail.user", "myuser");
 props.setProperty("mail.password", "mypwd");

其余的电子邮件发送机制如下所述。