Servlet - 傳送電子郵件

使用 Servlet 傳送電子郵件非常簡單，但首先您應該在您的機器上安裝 **JavaMail API** 和 **Java Activation Framework (JAF)**。

您可以從 Java 的標準網站下載最新版本的 JavaMail (版本 1.2)。
您可以從 Java 的標準網站下載最新版本的 JAF (版本 1.1.1)。

下載並解壓縮這些檔案，在新建立的頂級目錄中，您將找到這兩個應用程式的多個 jar 檔案。您需要將 **mail.jar** 和 **activation.jar** 檔案新增到您的 CLASSPATH 中。

傳送簡單的電子郵件

這是一個從您的機器傳送簡單電子郵件的示例。這裡假設您的 **localhost** 已連線到網際網路，並且能夠傳送電子郵件。同時確保 Java 電子郵件 API 包和 JAF 包中的所有 jar 檔案都存在於 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
      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();
      }
   }
}

現在讓我們編譯上面的 servlet 並在 web.xml 中建立以下條目

....
 <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>
....

現在使用 URL https://:8080/SendEmail 呼叫此 servlet，它將向給定的電子郵件 ID abcd@gmail.com 傳送電子郵件，並將顯示以下響應：

Send Email

Sent message successfully....

如果要向多個收件人傳送電子郵件，則可以使用以下方法指定多個電子郵件 ID：

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

以下是引數的說明：

type - 這將設定為 TO、CC 或 BCC。其中 CC 代表抄送，BCC 代表密送。例如 Message.RecipientType.TO
addresses - 這是電子郵件 ID 的陣列。在指定電子郵件 ID 時，您需要使用 InternetAddress() 方法。

傳送 HTML 電子郵件

這是一個從您的機器傳送 HTML 電子郵件的示例。這裡假設您的 **localhost** 已連線到網際網路，並且能夠傳送電子郵件。同時，請確保 Java 電子郵件 API 包和 JAF 包中的所有 jar 檔案都存在於 CLASSPATH 中。

此示例與上一個示例非常相似，只是這裡我們使用 setContent() 方法設定內容，其第二個引數為“text/html”，以指定訊息中包含 HTML 內容。

使用此示例，您可以傳送任意大小的 HTML 內容。

// 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();
      }
   }
}

編譯並執行上述 servlet 以向給定的電子郵件 ID 傳送 HTML 訊息。

在電子郵件中傳送附件

這是一個從您的機器傳送帶有附件的電子郵件的示例。這裡假設您的 **localhost** 已連線到網際網路，並且能夠傳送電子郵件。

// 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();
      }
   }
}

編譯並執行上述 servlet 以將檔案作為附件以及訊息一起傳送到給定的電子郵件 ID。

使用者身份驗證部分

如果需要向電子郵件伺服器提供使用者 ID 和密碼以進行身份驗證，則可以按如下方式設定這些屬性：

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

其餘的電子郵件傳送機制將保持如上所述。

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