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) 。

To send an email using your a Servlet is simple enough but to start with you should have JavaMail API and Java Activation Framework (JAF) installed on your machine.

You can download latest version of JavaMail (Version 1.2) from Java’s standard website.
You can download latest version of JAF (Version 1.1.1) from Java’s standard website.

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。

Download and unzip these files, in the newly created top level directories you will find a number of jar files for both the applications. You need to add mail.jar and activation.jar files in your CLASSPATH.

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。

Here is an example to send a simple email from your machine. Here it is assumed that your localhost is connected to the internet and capable enough to send an email. Same time make sure all the jar files from Java Email API package and JAF package are available in CLASSPATH.

// 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

Now let us compile the above servlet and create the following entries in web.xml

....
 <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 −

Now call this servlet using URL [role="bare"]http://localhost:8080/SendEmail which would send an email to given email ID abcd@gmail.com and would display following response −

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 −

If you want to send an email to multiple recipients then following methods would be used to specify multiple email IDs −

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

以下是参数说明 −

Here is the description of the parameters −

type − This would be set to TO, CC or BCC. Here CC represents Carbon Copy and BCC represents Black Carbon Copy. Example Message.RecipientType.TO
addresses − This is the array of email ID. You would need to use InternetAddress() method while specifying email IDs.

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。

Here is an example to send an HTML email from your machine. Here it is assumed that your localhost is connected to the internet and capable enough to send an email. At the same time, make sure all the jar files from Java Email API package and JAF package are available in CLASSPATH.

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。

This example is very similar to previous one, except here we are using setContent() method to set content whose second argument is "text/html" to specify that the HTML content is included in the message.

使用这个示例，你可以发送任意长度的 HTML 内容。

Using this example, you can send as big as HTML content you like.

// 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。

Compile and run the above servlet to send HTML message on a given email ID.

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。

Here is an example to send an email with attachment from your machine. Here it is assumed that your localhost is connected to the internet and capable enough to send an email.

// 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。

Compile and run above servlet to send a file as an attachment along with a message on a given email 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 −

If it is required to provide user ID and Password to the email server for authentication purpose then you can set these properties as follows −

 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。

Rest of the email sending mechanism would remain as explained above.