Demo1/src/RealEmailSender.java

import java.io.*;
import java.net.*;
import java.util.Base64;
import javax.net.ssl.*;

/**
 * 真实的邮件发送器
 * 使用原生Java实现SMTP协议发送邮件
 */
public class RealEmailSender {
    
    private static final String SMTP_HOST = "smtp.qq.com";
    private static final int SMTP_PORT = 587;
    
    /**
     * 发送邮件
     */
    public static boolean sendEmail(String fromEmail, String fromPassword, String toEmail, String subject, String content) {
        try {
            // 1. 连接到SMTP服务器
            Socket socket = new Socket(SMTP_HOST, SMTP_PORT);
            BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            PrintWriter writer = new PrintWriter(socket.getOutputStream(), true);
            
            // 2. 读取服务器欢迎信息
            String response = reader.readLine();
            System.out.println("服务器: " + response);
            if (!response.startsWith("220")) {
                throw new Exception("SMTP服务器连接失败");
            }
            
            // 3. 发送EHLO命令
            writer.println("EHLO localhost");
            response = readMultiLineResponse(reader);
            System.out.println("EHLO响应: " + response);
            
            // 4. 启动TLS加密
            writer.println("STARTTLS");
            response = reader.readLine();
            System.out.println("STARTTLS响应: " + response);
            if (!response.startsWith("220")) {
                throw new Exception("启动TLS失败");
            }
            
            // 5. 升级到SSL连接
            SSLSocketFactory factory = (SSLSocketFactory) SSLSocketFactory.getDefault();
            SSLSocket sslSocket = (SSLSocket) factory.createSocket(socket, SMTP_HOST, SMTP_PORT, true);
            sslSocket.startHandshake();
            
            // 6. 重新创建读写器
            reader = new BufferedReader(new InputStreamReader(sslSocket.getInputStream()));
            writer = new PrintWriter(sslSocket.getOutputStream(), true);
            
            // 7. 重新发送EHLO
            writer.println("EHLO localhost");
            response = readMultiLineResponse(reader);
            System.out.println("SSL EHLO响应: " + response);
            
            // 8. 认证
            writer.println("AUTH LOGIN");
            response = reader.readLine();
            System.out.println("AUTH响应: " + response);
            if (!response.startsWith("334")) {
                throw new Exception("认证失败");
            }
            
            // 9. 发送用户名（Base64编码）
            String encodedUsername = Base64.getEncoder().encodeToString(fromEmail.getBytes());
            writer.println(encodedUsername);
            response = reader.readLine();
            System.out.println("用户名响应: " + response);
            if (!response.startsWith("334")) {
                throw new Exception("用户名认证失败");
            }
            
            // 10. 发送密码（Base64编码）
            String encodedPassword = Base64.getEncoder().encodeToString(fromPassword.getBytes());
            writer.println(encodedPassword);
            response = reader.readLine();
            System.out.println("密码响应: " + response);
            if (!response.startsWith("235")) {
                throw new Exception("密码认证失败: " + response);
            }
            
            // 11. 发送邮件
            // MAIL FROM
            writer.println("MAIL FROM:<" + fromEmail + ">");
            response = reader.readLine();
            System.out.println("MAIL FROM响应: " + response);
            if (!response.startsWith("250")) {
                throw new Exception("MAIL FROM失败");
            }
            
            // RCPT TO
            writer.println("RCPT TO:<" + toEmail + ">");
            response = reader.readLine();
            System.out.println("RCPT TO响应: " + response);
            if (!response.startsWith("250")) {
                throw new Exception("RCPT TO失败");
            }
            
            // DATA
            writer.println("DATA");
            response = reader.readLine();
            System.out.println("DATA响应: " + response);
            if (!response.startsWith("354")) {
                throw new Exception("DATA失败");
            }
            
            // 邮件头和内容
            writer.println("From: " + fromEmail);
            writer.println("To: " + toEmail);
            writer.println("Subject: =?UTF-8?B?" + Base64.getEncoder().encodeToString(subject.getBytes("UTF-8")) + "?=");
            writer.println("MIME-Version: 1.0");
            writer.println("Content-Type: text/plain; charset=UTF-8");
            writer.println("Content-Transfer-Encoding: base64");
            writer.println("X-Mailer: MathLearningSystem");
            writer.println("X-Priority: 1");
            writer.println();
            writer.println(Base64.getEncoder().encodeToString(content.getBytes("UTF-8")));
            writer.println(".");
            
            response = reader.readLine();
            System.out.println("邮件发送响应: " + response);
            if (!response.startsWith("250")) {
                throw new Exception("邮件发送失败");
            }
            
            // 12. 退出
            writer.println("QUIT");
            response = reader.readLine();
            System.out.println("QUIT响应: " + response);
            
            // 13. 关闭连接
            sslSocket.close();
            
            System.out.println("邮件发送成功！");
            return true;
            
        } catch (Exception e) {
            System.err.println("邮件发送失败: " + e.getMessage());
            e.printStackTrace();
            return false;
        }
    }
    
    /**
     * 读取多行响应
     */
    private static String readMultiLineResponse(BufferedReader reader) throws IOException {
        StringBuilder response = new StringBuilder();
        String line;
        while ((line = reader.readLine()) != null) {
            response.append(line).append("\n");
            // 如果行不是以'-'结尾，说明是最后一行
            if (line.length() >= 4 && line.charAt(3) != '-') {
                break;
            }
        }
        return response.toString();
    }
    
    /**
     * 创建验证码邮件内容
     */
    public static String createVerificationEmailContent(String verificationCode) {
        return "您好！\n\n" +
               "您正在注册数学学习软件，您的验证码是：\n\n" +
               "验证码：" + verificationCode + "\n\n" +
               "验证码有效期为10分钟，请及时使用。\n" +
               "如果您没有注册我们的软件，请忽略此邮件。\n\n" +
               "祝您学习愉快！\n" +
               "数学学习软件团队\n\n" +
               "此邮件由系统自动发送，请勿回复。";
    }
}