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  Servlet - 发送电子邮件

  • 简述

    使用您的 Servlet 发送电子邮件很简单，但开始时您应该 JavaMail API 和 Java Activation Framework (JAF) 安装在你的机器上。
    下载并解压缩这些文件，在新创建的顶级目录中，您将找到两个应用程序的许多 jar 文件。你需要添加mail.jar 和 activation.jar CLASSPATH 中的文件。

  • 发送简单的电子邮件

    这是从您的机器发送简单电子邮件的示例。这里假设您的localhost已连接到 Internet 并且足以发送电子邮件。同时确保来自 Java Email API 包和 JAF 包的所有 jar 文件在 CLASSPATH 中可用。 
    
// 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();
      }
   }
}
    现在让我们编译上面的 servlet 并在 web.xml 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>
....
    现在使用 URL http://localhost:8080/SendEmail 调用这个 servlet，它将发送一封电子邮件到给定的电子邮件 ID abcd@gmail.com并显示以下响应 - 
    

Sent message successfully....
    如果您想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
    这是参数的描述 -
    • type- 这将设置为 TO、CC 或 BCC。这里CC代表Carbon Copy，BCC代表Black Carbon Copy。示例Message.RecipientType.TO
    • addresses- 这是电子邮件 ID 的数组。您需要在指定电子邮件 ID 时使用 InternetAddress() 方法。

  • 发送 HTML 电子邮件

    这是从您的机器发送 HTML 电子邮件的示例。这里假设您的localhost已连接到 Internet 并且足以发送电子邮件。同时，确保所有来自Java Email API 包和JAF 包的jar 文件在CLASSPATH 中可用。
    这个例子与前面的例子非常相似，除了这里我们使用 setContent() 方法来设置第二个参数是“text/html”的内容，以指定 HTML 内容包含在消息中。
    使用此示例，您可以发送尽可能大的 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 以在给定的电子邮件 ID 上发送 HTML 消息。

  • 在电子邮件中发送附件

    这是从您的机器发送带有附件的电子邮件的示例。这里假设您的localhost 已连接到 Internet 并且足以发送电子邮件。 
    
// 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();
      }
   }
}
    编译并在 servlet 之上运行，以将文件作为附件与给定电子邮件 ID 上的消息一起发送。

  • 用户认证部分

    如果需要向电子邮件服务器提供用户 ID 和密码以进行身份​​验证，那么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将保持如上文所述。
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