如何在邮件头中放入图像(Spring Boot)？

在邮件头中放入图像是通过在邮件的HTML内容中嵌入图像的方式实现的。具体步骤如下：

创建一个包含图像的HTML模板。可以使用<img>标签来插入图像，设置src属性为图像的URL或者Base64编码。例如：

<html>
<body>
    <img src="https://example.com/image.jpg" alt="Image">
</body>
</html>

在Spring Boot中，可以使用JavaMailSender发送邮件。首先，确保已经添加了相关的依赖，例如：

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

创建一个邮件服务类，注入JavaMailSender，并编写发送邮件的方法。例如：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.mail.javamail.JavaMailSender;
import org.springframework.mail.javamail.MimeMessageHelper;
import org.springframework.stereotype.Service;

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

@Service
public class EmailService {

    @Autowired
    private JavaMailSender javaMailSender;

    public void sendEmailWithImage(String recipient, String subject, String htmlContent) throws MessagingException {
        MimeMessage message = javaMailSender.createMimeMessage();
        MimeMessageHelper helper = new MimeMessageHelper(message, true);
        helper.setTo(recipient);
        helper.setSubject(subject);
        helper.setText(htmlContent, true);
        javaMailSender.send(message);
    }
}

在需要发送邮件的地方调用邮件服务类的方法，并传入收件人、主题和HTML内容。例如：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.mail.MessagingException;

@RestController
public class EmailController {

    @Autowired
    private EmailService emailService;

    @GetMapping("/sendEmail")
    public String sendEmail() {
        String recipient = "example@example.com";
        String subject = "Test Email with Image";
        String htmlContent = "<html><body><img src=\"https://example.com/image.jpg\" alt=\"Image\"></body></html>";

        try {
            emailService.sendEmailWithImage(recipient, subject, htmlContent);
            return "Email sent successfully";
        } catch (MessagingException e) {
            return "Failed to send email";
        }
    }
}

这样，当访问/sendEmail接口时，会发送一封包含图像的邮件到指定的收件人邮箱中。

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