Spring Boot – 通过 SMTP 发送电子邮件

Spring Boot提供了使用 JavaMail 库通过 SMTP 发送电子邮件的能力。在这里，我们将逐步说明开发可用于发送带或不带附件的电子邮件的 Restful Web 服务的指南。为了开始这些步骤，让我们首先使用 Spring Initializer 创建一个 Spring Boot 项目。

执行：

第一步：在pom.xml中添加spring-boot-starter-mail依赖。

XML

    org.springframework.boot
    spring-boot-starter-mail

这个依赖是使用JavaMail的入门，可以认为是 Spring Framework 的电子邮件发送支持

第 2 步：设置Application.properties文件，其中包含使用Gmail SMTP服务器所需的配置。

spring.mail.host=smtp.gmail.com
spring.mail.port=587
spring.mail.username=
spring.mail.password=
spring.mail.properties.mail.smtp.auth=true
spring.mail.properties.mail.smtp.starttls.enable=true

用于登录您的 Gmail 帐户的 Gmail ID 可以作为用户名提供。对于密码生成，需要为您的帐户启用两步验证，如下所示：

之后，需要使用以下路径创建AppPassword ：

Login to Gmail 
    -> Manage your Google Account 
        -> Security 
            -> App Passwords 
                -> Provide your login password 
                    -> Select app with a custom name 
                        -> Click on Generate

第 3 步：创建包含字段的EmailDetails类，例如 收件人、msgBody、主题和附件。

Java

// Java Program to Illustrate EmailDetails Class
 
package com.SpringBootEmail.Entity;
 
// Importing required classes
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
 
// Annotations
@Data
@AllArgsConstructor
@NoArgsConstructor
 
// Class
public class EmailDetails {
 
    // Class data members
    private String recipient;
    private String msgBody;
    private String subject;
    private String attachment;
}

第四步：创建接口EmailService ，实现服务层的EmailServiceImpl类。

EmailService接口定义了两个方法：

1. String sendSimpleMail(EmailDetails details)：此方法可用于向所需收件人发送简单的文本电子邮件。
2. String sendMailWithAttachment(EmailDetails details)：此方法可用于将电子邮件连同附件一起发送给所需的收件人。

接口和服务实现类如下图示例所示：

文件：电子邮件服务。Java

Java

// Java Program to Illustrate Creation Of
// Service Interface
 
package com.SpringBootEmail.service;
 
// Importing required classes
import com.SpringBootEmail.Entity.EmailDetails;
 
// Interface
public interface EmailService {
 
    // Method
    // To send a simple email
    String sendSimpleMail(EmailDetails details);
 
    // Method
    // To send an email with attachment
    String sendMailWithAttachment(EmailDetails details);
}

这里使用JavaMail API的JavaMailSender接口来发送简单的文本电子邮件。

要发送带有附件的更复杂的电子邮件，可以使用MimeMessage 。 MimeMessageHelper用作MimeMessage的帮助器类，用于添加发送邮件所需的附件和其他详细信息。

文件：EmailServiceImpl。Java

Java

// Java Program to Illustrate Creation Of
// Service implementation class
 
package com.SpringBootEmail.service;
 
// Importing required classes
import com.SpringBootEmail.Entity.EmailDetails;
import java.io.File;
import javax.mail.MessagingException;
import javax.mail.internet.MimeMessage;
import org.springframework.beans.factory.annotation.Autowired;
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.stereotype.Service;
 
// Annotation
@Service
// Class
// Implementing EmailService interface
public class EmailServiceImpl implements EmailService {
 
    @Autowired private JavaMailSender javaMailSender;
 
    @Value("${spring.mail.username}") private String sender;
 
    // Method 1
    // To send a simple email
    public String sendSimpleMail(EmailDetails details)
    {
 
        // Try block to check for exceptions
        try {
 
            // Creating a simple mail message
            SimpleMailMessage mailMessage
                = new SimpleMailMessage();
 
            // Setting up necessary details
            mailMessage.setFrom(sender);
            mailMessage.setTo(details.getRecipient());
            mailMessage.setText(details.getMsgBody());
            mailMessage.setSubject(details.getSubject());
 
            // Sending the mail
            javaMailSender.send(mailMessage);
            return "Mail Sent Successfully...";
        }
 
        // Catch block to handle the exceptions
        catch (Exception e) {
            return "Error while Sending Mail";
        }
    }
 
    // Method 2
    // To send an email with attachment
    public String
    sendMailWithAttachment(EmailDetails details)
    {
        // Creating a mime message
        MimeMessage mimeMessage
            = javaMailSender.createMimeMessage();
        MimeMessageHelper mimeMessageHelper;
 
        try {
 
            // Setting multipart as true for attachments to
            // be send
            mimeMessageHelper
                = new MimeMessageHelper(mimeMessage, true);
            mimeMessageHelper.setFrom(sender);
            mimeMessageHelper.setTo(details.getRecipient());
            mimeMessageHelper.setText(details.getMsgBody());
            mimeMessageHelper.setSubject(
                details.getSubject());
 
            // Adding the attachment
            FileSystemResource file
                = new FileSystemResource(
                    new File(details.getAttachment()));
 
            mimeMessageHelper.addAttachment(
                file.getFilename(), file);
 
            // Sending the mail
            javaMailSender.send(mimeMessage);
            return "Mail sent Successfully";
        }
 
        // Catch block to handle MessagingException
        catch (MessagingException e) {
 
            // Display message when exception occurred
            return "Error while sending mail!!!";
        }
    }
}

第 5 步：创建一个 Rest Controller EmailController ，它定义了用于发送电子邮件的各种 API。

Java

// Java Program to Create Rest Controller that
// Defines various API for Sending Mail
 
package com.SpringBootEmail.controller;
 
// Importing required classes
import com.SpringBootEmail.Entity.EmailDetails;
import com.SpringBootEmail.service.EmailService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;
 
// Annotation
@RestController
// Class
public class EmailController {
 
    @Autowired private EmailService emailService;
 
    // Sending a simple Email
    @PostMapping("/sendMail")
    public String
    sendMail(@RequestBody EmailDetails details)
    {
        String status
            = emailService.sendSimpleMail(details);
 
        return status;
    }
 
    // Sending email with attachment
    @PostMapping("/sendMailWithAttachment")
    public String sendMailWithAttachment(
        @RequestBody EmailDetails details)
    {
        String status
            = emailService.sendMailWithAttachment(details);
 
        return status;
    }
}

第 6 步：运行 Spring Boot 应用程序并点击http://localhost:8080/sendMail发送一封简单的电子邮件

Gmail 收到的邮件如下：

第 7 步：运行 Spring Boot 应用程序并点击http://localhost:8080/sendMailWithAttachment以发送电子邮件和附件。

Gmail 收到的邮件如下：