Java的发送邮件

以下内容引用自http://wiki.jikexueyuan.com/project/java/sending-email.html：

用Java应用程序来发送一封电子邮件是足够简单的，但是开始时应该在机器上安装有JavaMail API和Java Activation Framework(JAF)。

• 可以从Java的标准企业网站上下载最新的JavaMail（1.2 版本）版本。
• 可以从Java的标准企业网站上下载最新的JAF（1.1.1 版本）版本。

下载并解压这些文件，在新创建的顶级目录中将找到许多应用程序的jar文件。需要CLASSPATH中添加mail.jar和activation.jar文件。（POM项目和Eclipse工程省略这一步）

一、发送一封简单的电子邮件

这是从机器中发送一封简单的电子邮件的例子。这里假设本地主机连接到了因特网并且能够发送一封电子邮件。

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";//This is SMTP Server,Ex:smtp.163.com
        
        // set email username
        String user = "user";
        
        // set email password
        String password = "password";

        // Get system properties
        Properties properties = System.getProperties();

        // Setup mail server
        properties.setProperty("mail.smtp.host", host);
        properties.setProperty("mail.user", user);
        properties.setProperty("mail.password", password);

        // 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来发送一封简单的电子邮件：
$ java SendEmail
Sent message successfully....

如果想要给多个收信者发送一封电子邮件，那么以下的方法将被用来发送给指定的多个电子邮件ID：

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

这是参数的描述：

• type：这将被设置为TO，CC或者BCC。这里CC表示副本，BCC表示Black Carbon Copy。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，需要使用InternetAddress()。

二、发送一封HTML电子邮件

这是从机器发送一封HTML电子邮件的例子。这里假设本地主机连接到了因特网并且能够发送一封电子邮件。

这个例子和前一个非常相似，除了在这用setContent()方法来设置第二个参数为"text/html"以指定 HTML 内容被包括在消息中的内容。

使用这个例子，可以发送任何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";//This is SMTP Server,Ex:smtp.163.com
        
        // set email username
        String user = "user";
        
        // set email password
        String password = "password";
        
        // Get system properties
        Properties properties = System.getProperties();

        // Setup mail server
        properties.setProperty("mail.smtp.host", host);
        properties.setProperty("mail.user", user);
        properties.setProperty("mail.password", password);


        // 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一封 HTML 的电子邮件：
$ java SendHTMLEmail
Sent message successfully....

三、发送电子邮件中的附件

这是一个从机器中发送一封带有附件的电子邮件的例子。这里假设本地主机连接到了因特网并且能够发送一封电子邮件。

//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";// This is SMTP Server,Ex:smtp.163.com

        // set email username
        String user = "user";

        // set email password
        String password = "password";

        // Get system properties
        Properties properties = System.getProperties();

        // Setup mail server
        properties.setProperty("mail.smtp.host", host);
        properties.setProperty("mail.user", user);
        properties.setProperty("mail.password", password);

        // 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一封 HTML 电子邮件：
$ java SendFileEmail
Sent message successfully....

四、用户身份认证部分

如果为了身份认证的目的需要给电子邮件服务器提供用户ID和密码，可以像这样设置这些属性：

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

电子邮件发送机制的剩余部分和上述解释的一样。

测试工程：https://github.com/easonjim/5_java_example/tree/master/javabasicstest/test27