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发送电子邮件

使用 Servlet 发送一封电子邮件是非常简单的,但是开始之前你必须在你的计算机上安装 JavaMail APIJava Activation Framework(JAF)

下载并解压缩这些文件,在新创建的顶级目录中你会发现这两个应用程序的一些 jar 文件。你需要把 mail.jaractivation.jar 文件添加到你的 CLASSPATH 中。

发送一封简单的电子邮件

这是从你的计算机上发送一封简单的电子邮件的实例。这里假设你的本地主机已连接到互联网并可以发送电子邮件。同时确保来自 Java Email API 包和 JAF 包的所有的 jar 文件在 CLASSPATH 中是可用的。

// 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();
      }
   }
} 

现在让我们来编译上述 servlet 并在 web.xml 文件中创建以下条目:

....
 <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 来调用这个 servlet。这将会给给定的电子邮件 ID abcd@gmail.com 发送一封电子邮件并将显示如下所示的响应:

Send Email

Sent message successfully....

如果你想把一封电子邮件发送给多个收件人,那么使用下面的方法来指定多个电子邮件 ID:

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

这里是对参数的描述:

  • type:这将被设置为 TO、CC 或 BCC。这里 CC 代表抄送且 BCC 代表密件抄送。例如 Message.RecipientType.TO

  • addresses:这是电子邮件 ID 的数组。当指定电子邮件 ID 时,你需要使用 InternetAddress() 方法。

发送一封 HTML 电子邮件

这个例子将从你的计算机上发送一封 HTML 电子邮件。这里假设你的本地主机已连接到互联网且可以发送电子邮件。同时确保来自 Java Email API 包和 JAF 包的所有的 jar 文件在 CLASSPATH 中都是可用的。

这个例子与上一个例子非常相似,除了在这里我们使用的是 setContent() 方法来设置内容,它的第二个参数为 “text/html” 用来指定 HTML 内容是包含在消息中的。

使用这个实例,你可以发送内容大小不限的 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 来在给定的电子邮件 ID 上发送 HTML 消息。

在电子邮件中发送附件

这里的例子将从你的计算机上发送一封带有附件的电子邮件。这里假设你的本地主机已连接到互联网并能够发送电子邮件。同时确保来自 Java Email API 包和 JAF 包的所有的 jar 文件在 CLASSPATH 中都是可用的。

// 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();
      }
   }
} 

编译并运行上面的 servlet 来在给定的电子邮件 ID 上发送附件文件和消息。

用户身份认证部分

如果需要向电子邮件服务器提供用户 ID 和密码来进行身份认证,那么你可以设置如下所示的属性:

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

电子邮件发送机制的其余部分与上面解释的一致。

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