使用Java应用程序发送邮件是很简单的，需要安装JavaMail API 和Java Activation Framework (JAF) 在机器上。

• 可以从Java的标准网站上下载JavaMail（版本1.2）的最新版本。

• 可以从Java的标准网站下载最新版本的JAF（版本1.1.1）。

下载并解压缩这些文件，在新创建的顶层目录，会发现一些jar文件应用。需要添加了mail.jar和activation.jar文件在CLASSPATH中。

发送一个简单的E-mail：

下面是一个例子，从机器发送一个简单的电子邮件。这里假设你的电脑已经可以连接到互联网，并有足够的能力来发送电子邮件。

// File Name SendEmail.java

import java.util.*;
import javax.mail.*;
import javax.mail.internet.*;
import javax.activation.*;

public class SendEmail
{
   public static void main(String [] args)
   {    
      // 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);

      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);
         System.out.println("Sent message successfully....");
      }catch (MessagingException mex) {
         mex.printStackTrace();
      }
   }
}

编译并运行这个程序发送一个简单的电子邮件：

$ java SendEmail
Sent message successfully....

如果想发送电子邮件给多个收件人，然后下面的方法将被用来指定多个电子邮件标识：

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

这里的参数的说明：

• type: 这将被设定为TO，CC或BCC。在这里，CC代表抄送和BCC代表黑抄送。例子Message.RecipientType.TO

• addresses: 这是电子邮件的ID的数组。需要使用InternetAddress() 方法，同时指定电子邮件ID

Send an HTML E-mail:

下面是一个例子，从机器发送的HTML电子邮件。这里假设你的本地主机连接到互联网，并有足够的能力来发送电子邮件。

这个例子非常相似，前一个，除了在这里我们使用的是使用setContent()方法来设置内容的第二个参数是"text/html"类型指定的HTML内容被包含在消息中。

通过这个例子，可以发送大如喜欢HTML内容。

// File Name SendHTMLEmail.java

import java.util.*;
import javax.mail.*;
import javax.mail.internet.*;
import javax.activation.*;

public class SendHTMLEmail
{
   public static void main(String [] args)
   {
      
      // 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);

      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);
         System.out.println("Sent message successfully....");
      }catch (MessagingException mex) {
         mex.printStackTrace();
      }
   }
}

编译并运行这个程序来发送HTML电子邮件：

$ java SendHTMLEmail
Sent message successfully....

发送附件的电子邮件：

下面是一个例子与附件从机器发送电子邮件。这里假设你的本地主机连接到互联网，并有足够的能力来发送电子邮件。

// File Name SendFileEmail.java

import java.util.*;
import javax.mail.*;
import javax.mail.internet.*;
import javax.activation.*;

public class SendFileEmail
{
   public static void main(String [] args)
   {
      
      // 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);

      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);
         System.out.println("Sent message successfully....");
      }catch (MessagingException mex) {
         mex.printStackTrace();
      }
   }
}

编译并运行这个程序来发送HTML电子邮件：

$ java SendFileEmail
Sent message successfully....

用户认证部分：

如果需要提供用户ID和密码的电子邮件服务器进行身份验证的目的，那么可以按如下方法设置这些属性：

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

邮件发送机制的其余部分将继续如上面所述。

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