使用最新技术实现Java邮件发送功能

一、技术选型说明

在Java邮件发送领域，传统的JavaMail API虽然稳定，但配置繁琐。随着微服务和响应式编程的兴起，结合Spring Boot和MailHog等工具，我们可以构建更高效、更易于测试的邮件发送系统。

（一）核心技术栈

• Spring Boot 3.0+：简化配置，提供自动配置功能
• Jakarta Mail API：JavaMail的最新版本，支持Jakarta EE标准
• MailHog：本地邮件测试工具，避免测试邮件发送到真实邮箱
• 响应式编程：使用Spring WebFlux实现异步邮件发送
• Thymeleaf：模板引擎生成HTML邮件内容

（二）依赖管理

在Maven项目中添加以下依赖：

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-mail</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-webflux</artifactId>
</dependency>
<dependency>
    <groupId>org.thymeleaf</groupId>
    <artifactId>thymeleaf-spring6</artifactId>
</dependency>

二、开发环境搭建

（一）本地测试邮件服务器部署

使用Docker快速部署MailHog：

docker run -d -p 1025:1025 -p 8025:8025 mailhog/mailhog

• SMTP服务器地址：localhost:1025（无需认证）
• Web界面：http://localhost:8025 （查看收到的邮件）

（二）Spring Boot配置

在application.yml中配置邮件服务：

spring:
  mail:
    host: localhost
    port: 1025
    username: test
    password: test
    properties:
      mail:
        smtp:
          auth: false
          starttls:
            enable: false
  thymeleaf:
    cache: false
    prefix: classpath:/templates/
    suffix: .html

三、响应式邮件服务实现

（一）邮件配置类

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.mail.javamail.JavaMailSender;
import org.springframework.mail.javamail.JavaMailSenderImpl;
import java.util.Properties;

@Configuration
public class MailConfig {
   

    @Bean
    public JavaMailSender javaMailSender() {
   
        JavaMailSenderImpl mailSender = new JavaMailSenderImpl();
        mailSender.setHost("localhost");
        mailSender.setPort(1025);
        Properties props = mailSender.getJavaMailProperties();
        props.put("mail.transport.protocol", "smtp");
        props.put("mail.smtp.auth", "false");
        props.put("mail.smtp.starttls.enable", "false");
        return mailSender;
    }
}

（二）邮件模板服务

import org.springframework.stereotype.Service;
import org.thymeleaf.TemplateEngine;
import org.thymeleaf.context.Context;

@Service
public class MailTemplateService {
   

    private final TemplateEngine templateEngine;

    public MailTemplateService(TemplateEngine templateEngine) {
   
        this.templateEngine = templateEngine;
    }

    public String generateHtmlContent(String templateName, Context context) {
   
        return templateEngine.process(templateName, context);
    }
}

（三）异步邮件服务

import org.springframework.mail.javamail.JavaMailSender;
import org.springframework.mail.javamail.MimeMessageHelper;
import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Service;
import reactor.core.publisher.Mono;

import javax.mail.MessagingException;
import javax.mail.internet.MimeMessage;

@Service
public class MailService {
   

    private final JavaMailSender mailSender;
    private final MailTemplateService templateService;

    public MailService(JavaMailSender mailSender, MailTemplateService templateService) {
   
        this.mailSender = mailSender;
        this.templateService = templateService;
    }

    @Async
    public Mono<Void> sendHtmlEmail(String to, String subject, String templateName, Object model) {
   
        return Mono.fromRunnable(() -> {
   
            MimeMessage message = mailSender.createMimeMessage();
            try {
   
                MimeMessageHelper helper = new MimeMessageHelper(message, true, "UTF-8");
                helper.setTo(to);
                helper.setSubject(subject);
                helper.setText(buildContent(templateName, model), true);
                mailSender.send(message);
            } catch (MessagingException e) {
   
                throw new RuntimeException("Failed to send email", e);
            }
        });
    }

    private String buildContent(String templateName, Object model) {
   
        var context = new Context();
        context.setVariable("data", model);
        return templateService.generateHtmlContent(templateName, context);
    }
}

四、HTML邮件模板示例

在src/main/resources/templates目录下创建welcome.html：

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>欢迎注册</title>
</head>
<body style="font-family: Arial, sans-serif;">
    <div style="max-width: 600px; margin: 0 auto; padding: 20px;">
        <h1 style="color: #333;">欢迎加入我们，<span th:text="${data.username}">用户</span>！</h1>
        <p style="color: #666;">感谢您注册我们的服务，请点击下方按钮验证您的邮箱：</p>
        <a href="#" th:href="${data.verificationUrl}" 
           style="display: inline-block; background-color: #4CAF50; color: white; 
                  padding: 10px 20px; text-decoration: none; border-radius: 5px;">
            验证邮箱
        </a>
        <p style="color: #999; margin-top: 20px;">如果按钮无法点击，请复制以下链接到浏览器中打开：</p>
        <p style="color: #666; word-break: break-all;"><span th:text="${data.verificationUrl}"></span></p>
    </div>
</body>
</html>

五、邮件发送控制器

import org.springframework.web.bind.annotation.*;
import reactor.core.publisher.Mono;

import java.util.HashMap;
import java.util.Map;

@RestController
@RequestMapping("/api/mail")
public class MailController {
   

    private final MailService mailService;

    public MailController(MailService mailService) {
   
        this.mailService = mailService;
    }

    @PostMapping("/send")
    public Mono<String> sendEmail(@RequestBody EmailRequest request) {
   
        Map<String, Object> model = new HashMap<>();
        model.put("username", request.getUsername());
        model.put("verificationUrl", "https://example.com/verify?token=" + request.getToken());

        return mailService.sendHtmlEmail(
                request.getTo(),
                "欢迎注册",
                "welcome",
                model
            )
            .thenReturn("邮件发送成功")
            .onErrorResume(e -> Mono.just("邮件发送失败: " + e.getMessage()));
    }
}

record EmailRequest(String to, String username, String token) {
   }

六、测试与部署

（一）单元测试

import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import reactor.test.StepVerifier;

@SpringBootTest
public class MailServiceTest {
   

    @Autowired
    private MailService mailService;

    @Test
    public void testSendHtmlEmail() {
   
        Map<String, Object> model = Map.of(
            "username", "测试用户",
            "verificationUrl", "https://example.com/test"
        );

        StepVerifier.create(mailService.sendHtmlEmail(
                "test@example.com",
                "单元测试邮件",
                "welcome",
                model
            ))
            .verifyComplete();
    }
}

（二）生产环境配置

在生产环境中，修改application-prod.yml配置：

spring:
  mail:
    host: smtp.qq.com
    port: 465
    username: your_email@qq.com
    password: your_authorization_code
    properties:
      mail:
        smtp:
          auth: true
          ssl:
            enable: true

七、性能优化与最佳实践

（一）连接池配置

在application.yml中添加连接池配置：

spring:
  mail:
    properties:
      mail:
        smtp:
          connectiontimeout: 5000
          timeout: 3000
          writetimeout: 5000
          pool:
            enabled: true
            max-connections: 5

（二）邮件队列处理

使用RabbitMQ或Kafka实现邮件异步队列处理，避免阻塞主业务流程：

import org.springframework.amqp.rabbit.annotation.RabbitListener;
import org.springframework.stereotype.Service;

@Service
public class MailConsumer {
   

    private final MailService mailService;

    public MailConsumer(MailService mailService) {
   
        this.mailService = mailService;
    }

    @RabbitListener(queues = "mailQueue")
    public void processEmail(EmailMessage message) {
   
        mailService.sendHtmlEmail(
            message.getTo(),
            message.getSubject(),
            message.getTemplate(),
            message.getModel()
        ).subscribe();
    }
}

（三）邮件发送监控

集成Spring Boot Actuator监控邮件发送指标：

import io.micrometer.core.annotation.Timed;
import org.springframework.stereotype.Service;

@Service
public class MonitoredMailService {
   

    private final MailService mailService;

    public MonitoredMailService(MailService mailService) {
   
        this.mailService = mailService;
    }

    @Timed(value = "mail.send.time", description = "Time taken to send an email")
    public Mono<Void> sendMonitoredEmail(String to, String subject, String template, Object model) {
   
        return mailService.sendHtmlEmail(to, subject, template, model);
    }
}

通过以上配置和实现，我们构建了一个现代化的Java邮件发送系统，支持异步处理、HTML模板、邮件队列和性能监控，满足企业级应用的需求。

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代码获取方式
https://pan.quark.cn/s/14fcf913bae6