Servlet - 发送电子邮件

使用 Servlet 发送电子邮件非常简单，但首先您应该在计算机上安装JavaMail API和Java 激活框架 (JAF) 。

您可以从 Java 的标准网站下载最新版本的JavaMail（版本 1.2）。
您可以从 Java 标准网站下载最新版本的JAF（版本 1.1.1）。

下载并解压这些文件，在新创建的顶级目录中，您将找到这两个应用程序的许多 jar 文件。您需要在 CLASSPATH 中添加mail.jar和activation.jar文件。

发送简单的电子邮件

以下是从您的计算机发送简单电子邮件的示例。这里假设您的本地主机已连接到互联网并且有足够的能力发送电子邮件。同时确保 Java Email API 包和 JAF 包中的所有 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 调用此 servlet，它将向给定的电子邮件 ID abcd@gmail.com发送电子邮件，并显示以下响应 -

Send Email

Sent message successfully....

如果您想向多个收件人发送电子邮件，则可以使用以下方法来指定多个电子邮件 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代表抄送，BCC代表黑抄送。示例Message.RecipientType.TO
地址- 这是电子邮件 ID 的数组。在指定电子邮件 ID 时，您需要使用 InternetAddress() 方法。

发送 HTML 电子邮件

以下是从您的计算机发送 HTML 电子邮件的示例。这里假设您的本地主机已连接到互联网并且有足够的能力发送电子邮件。同时，确保Java Email API包和JAF包中的所有jar文件在CLASSPATH中可用。

此示例与上一个示例非常相似，只不过这里我们使用 setContent() 方法来设置第二个参数为“text/html”的内容，以指定消息中包含 HTML 内容。

使用此示例，您可以发送任意大小的 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，以通过给定的电子邮件 ID 发送 HTML 消息。

通过电子邮件发送附件

以下是从您的计算机发送带有附件的电子邮件的示例。这里假设您的本地主机已连接到互联网并且有足够的能力发送电子邮件。

// 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");

电子邮件发送机制的其余部分将保持如上所述。