使用 SSL/TLS 身份验证通过Java发送电子邮件

JavaMail API 定义了代表邮件系统组件的类。 JavaMail 不实现电子邮件服务器，相反，它允许您使用Java API 访问电子邮件服务器。为了测试提供的代码，您必须有权访问电子邮件服务器。虽然 JavaMail API 规范不要求支持特定协议，但 JavaMail 通常包括对 POP3、IMAP 和 SMTP 的支持。

电子邮件如何工作？

先决条件：

• 有权访问 SMTP 服务器。您必须知道 SMTP 服务器的主机名、端口号和安全设置。 Webmail 提供商可能会提供 SMTP 访问、查看您的电子邮件帐户设置或帮助查找更多信息。请注意，您的用户名通常是您的完整电子邮件地址，而不仅仅是 @ 符号之前的名称。
  
• Java EE IDE 和应用程序服务器，例如 GlassFish 或 Oracle WebLogic Server。 JavaMail 可以作为库下载到Java SE 应用程序中，但本教程假定使用已经包含 JavaMail 的Java EE 应用程序服务器。

使用 JavaMail 发送电子邮件有以下三个步骤。它们如下：

获取会话对象——javax.mail.Session类提供会话对象、Session.getDefaultInstance() 方法和 Session.getInstance() 方法。

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

// mail username and password   
properties.setProperty("mail.user", "user");                   
properties.setProperty("mail.password", "password$$");           

编写消息——javax.mail.Transport类提供发送消息的方法。

// javax.mail.internet.MimeMessage class is
// mostly used for abstraction. 
MimeMessage message = new MimeMessage(session);

// header field of the header.  
message.setFrom(new InternetAddress(from)); 
message.addRecipient(Message.RecipientType.TO, 
                     new InternetAddress(to));  
message.setSubject("subject");  
message.setText("Hello, aas is sending email ");  

发送消息

Transport.send(message);

以下是使用 SMTP 在Java中发送邮件而无需在Java中完整实现的身份验证 -

Java

import java.util.*;
import javax.mail.*;
import javax.mail.internet.*;
import javax.activation.*;
 
public class SendEmail {
     
    public static void main(String[] args)
    {
        // change below lines accordingly
        String to = "[e-mail]";
        String from = "[e-mail]";
        String host = "localhost"; // or IP address
 
        // Get the session object
        // 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);
 
        // compose the message
        try {
 
            // javax.mail.internet.MimeMessage class
            // is mostly used for abstraction.
            MimeMessage message = new MimeMessage(session);
 
            // header field of the header.
            message.setFrom(new InternetAddress(from));
            message.addRecipient(Message.RecipientType.TO,
                                new InternetAddress(to));
            message.setSubject("subject");
            message.setText("Hello, aas is sending email ");
 
            // Send message
            Transport.send(message);
            System.out.println("Yo it has been sent..");
        }
        catch (MessagingException mex) {
            mex.printStackTrace();
        }
    }
}

输出

Yo it has been sent...

该程序易于理解且运行良好，但在现实生活中，大多数 SMTP 服务器使用某种身份验证，例如 TLS 或 SSL 身份验证。因此，我们现在将看到如何为这些身份验证协议创建一个 Session 对象。对于 TLS 和 SSL，您可以知道运行这些服务的邮件服务器所在的端口。我们将为您提供考虑到 Gmail 的代码。以下是使用 SMTP 和 TLS 身份验证在Java中的完整实现在Java中发送邮件 -

Java

import java.util.*;
import javax.mail.*;
import javax.mail.internet.*;
import javax.activation.*;
 
public class SendMail {
 
    public static void main(String[] args) {
         
        // change accordingly
        final String username = "[e-mail]";  
         
        // change accordingly
        final String password = "password";
         
        // or IP address
        final String host = "localhost";
 
        // Get system properties
        Properties props = new Properties();            
         
        // enable authentication
        props.put("mail.smtp.auth", "true");              
         
        // enable STARTTLS
        props.put("mail.smtp.starttls.enable", "true");   
         
        // Setup mail server
        props.put("mail.smtp.host", "smtp.gmail.com");    
         
        // TLS Port
        props.put("mail.smtp.port", "587");               
 
        // creating Session instance referenced to
        // Authenticator object to pass in
        // Session.getInstance argument
        Session session = Session.getInstance(props,
          new javax.mail.Authenticator() {
            
            //override the getPasswordAuthentication method
            protected PasswordAuthentication
                           getPasswordAuthentication() {
                                        
                return new PasswordAuthentication(username,
                                                 password);
            }
          });
 
        try {
             
            // compose the message
            // javax.mail.internet.MimeMessage class is
            // mostly used for abstraction.
            Message message = new MimeMessage(session);   
             
            // header field of the header.
            message.setFrom(new InternetAddress("[e-mail]"));
             
            message.setRecipients(Message.RecipientType.TO,
                InternetAddress.parse("[e-mail]"));
            message.setSubject("hello");
            message.setText("Yo it has been sent");
 
            Transport.send(message);         //send Message
 
            System.out.println("Done");
 
        } catch (MessagingException e) {
            throw new RuntimeException(e);
        }
    }
}

以下是在 Java 中使用带有 SSL 身份验证的 SMTP 发送邮件的Java完整Java-

Java

import java.util.*;
import javax.mail.*;
import javax.mail.internet.*;
import javax.activation.*;
 
public class SendEmail {
public static void main(String[] args)
    {  
        // change accordingly
        String to = "[e-mail]";
         
        // change accordingly
        String from = "[e-mail]";
         
        // or IP address
        String host = "localhost";
         
        // mail id
        final String username = "[e-mail]"
         
        // correct password for gmail id
        final String password = "mypassword";
 
        System.out.println("TLSEmail Start");
        // Get the session object
         
        // Get system properties
        Properties properties = System.getProperties();
         
        // Setup mail server
        properties.setProperty("mail.smtp.host", host);
         
        // SSL Port
        properties.put("mail.smtp.port", "465");
         
        // enable authentication
        properties.put("mail.smtp.auth", "true");
         
        // SSL Factory
        properties.put("mail.smtp.socketFactory.class",
                "javax.net.ssl.SSLSocketFactory"); 
 
        // creating Session instance referenced to
        // Authenticator object to pass in
        // Session.getInstance argument
        Session session = Session.getDefaultInstance(props,
            new javax.mail.Authenticator() {
                 
                // override the getPasswordAuthentication
                // method
                protected PasswordAuthentication
                        getPasswordAuthentication() {
                    return new PasswordAuthentication("username",
                                                    "password");
                }
            });
}
 
 //compose the message
try {
    // javax.mail.internet.MimeMessage class is mostly
    // used for abstraction.
    MimeMessage message = new MimeMessage(session);
     
    // header field of the header.
    message.setFrom(new InternetAddress(from));
     
    message.addRecipient(Message.RecipientType.TO,
                          new InternetAddress(to));
    message.setSubject("subject");
    message.setText("Hello, aas is sending email ");
 
    // Send message
    Transport.send(message);
    System.out.println("Yo it has been sent..");
}
catch (MessagingException mex) {
    mex.printStackTrace();
}
}
}

多个客户端我们可以对上面的代码进行如下改动
 

Java

// This is an array of e-mail ID. You would
// need to use InternetAddress() method
// while specifying email IDs
void addRecipients(Message.RecipientType type,
                        Address[] addresses)