Hướng Dẫn Gửi Email Bằng Gmail Trong Spring Boot / Spring MVC (Từ A Đến Z)

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<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-mail</artifactId>
</dependency>

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implementation 'org.springframework.boot:spring-boot-starter-mail'

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spring:
  mail:
    host: smtp.gmail.com
    port: 587
    username: your-email@gmail.com
    # Khuyến nghị lấy từ biến môi trường: ${MAIL_PASSWORD}
    password: abcd efgh ijkl mnop # Mật khẩu ứng dụng 16 ký tự vừa tạo
    properties:
      mail:
        smtp:
          auth: true
          starttls:
            enable: true
            required: true
          connectiontimeout: 5000
          timeout: 5000
          writetimeout: 5000

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spring.mail.host=smtp.gmail.com
spring.mail.port=587
spring.mail.username=your-email@gmail.com
spring.mail.password=abcd efgh ijkl mnop
spring.mail.properties.mail.smtp.auth=true
spring.mail.properties.mail.smtp.starttls.enable=true
spring.mail.properties.mail.smtp.starttls.required=true
spring.mail.properties.mail.smtp.connectiontimeout=5000
spring.mail.properties.mail.smtp.timeout=5000
spring.mail.properties.mail.smtp.writetimeout=5000

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package com.example.emaildemo.service;

import jakarta.mail.MessagingException;
import jakarta.mail.internet.MimeMessage;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.core.io.FileSystemResource;
import org.springframework.mail.SimpleMailMessage;
import org.springframework.mail.javamail.JavaMailSender;
import org.springframework.mail.javamail.MimeMessageHelper;
import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Service;

import java.io.File;

@Service
public class EmailService {

    private final JavaMailSender mailSender;

    @Value("${spring.mail.username}")
    private String senderEmail;

    public EmailService(JavaMailSender mailSender) {
        this.mailSender = mailSender;
    }

    /**
     * 1. Gửi email văn bản đơn giản (Plain Text)
     */
    public void sendSimpleEmail(String to, String subject, String body) {
        SimpleMailMessage message = new SimpleMailMessage();
        message.setFrom(senderEmail);
        message.setTo(to);
        message.setSubject(subject);
        message.setText(body);

        mailSender.send(message);
    }

    /**
     * 2. Gửi email định dạng HTML phong phú
     */
    public void sendHtmlEmail(String to, String subject, String htmlContent) throws MessagingException {
        MimeMessage message = mailSender.createMimeMessage();
        
        // true: multipart mode hỗ trợ HTML và đính kèm
        MimeMessageHelper helper = new MimeMessageHelper(message, true, "UTF-8");
        
        helper.setFrom(senderEmail);
        helper.setTo(to);
        helper.setSubject(subject);
        helper.setText(htmlContent, true); // true = isHtml

        mailSender.send(message);
    }

    /**
     * 3. Gửi email kèm tệp đính kèm (Attachment)
     */
    public void sendEmailWithAttachment(String to, String subject, String body, String attachmentPath) throws MessagingException {
        MimeMessage message = mailSender.createMimeMessage();
        MimeMessageHelper helper = new MimeMessageHelper(message, true, "UTF-8");

        helper.setFrom(senderEmail);
        helper.setTo(to);
        helper.setSubject(subject);
        helper.setText(body);

        // Đính kèm tệp tin
        FileSystemResource file = new FileSystemResource(new File(attachmentPath));
        if (file.exists()) {
            helper.addAttachment(file.getFilename(), file);
        }

        mailSender.send(message);
    }
}

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package com.example.emaildemo.controller;

import com.example.emaildemo.service.EmailService;
import jakarta.mail.MessagingException;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;

@RestController
@RequestMapping("/api/v1/emails")
public class EmailController {

    private final EmailService emailService;

    public EmailController(EmailService emailService) {
        this.emailService = emailService;
    }

    @PostMapping("/send-simple")
    public ResponseEntity<String> sendSimpleEmail(@RequestParam String to) {
        emailService.sendSimpleEmail(
                to,
                "Chào mừng bạn đến với ứng dụng!",
                "Cảm ơn bạn đã đăng ký tài khoản thành công."
        );
        return ResponseEntity.ok("Gửi email thành công!");
    }

    @PostMapping("/send-html")
    public ResponseEntity<String> sendHtmlEmail(@RequestParam String to) throws MessagingException {
        String html = """
                <div style="font-family: Arial, sans-serif; padding: 20px; border: 1px solid #e0e0e0; border-radius: 8px;">
                    <h2 style="color: #2563eb;">Xác thực tài khoản của bạn</h2>
                    <p>Xin chào,</p>
                    <p>Mã OTP xác thực của bạn là: <strong style="font-size: 20px; color: #dc2626;">892145</strong></p>
                    <p>Mã này có hiệu lực trong vòng 5 phút.</p>
                    <hr/>
                    <small style="color: #6b7280;">Nếu bạn không yêu cầu mã này, vui lòng bỏ qua email.</small>
                </div>
                """;

        emailService.sendHtmlEmail(to, "Mã xác thực OTP đăng ký", html);
        return ResponseEntity.ok("Gửi email HTML thành công!");
    }
}

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export MAIL_USERNAME="your-email@gmail.com"
export MAIL_PASSWORD="your-16-char-app-password"

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spring:
  mail:
    username: ${MAIL_USERNAME}
    password: ${MAIL_PASSWORD}